Page 1 of 2 12 LastLast
Results 1 to 20 of 28

Thread: Jet Motor--Inboard vs. Outboard?

  1. #1

    Default Jet Motor--Inboard vs. Outboard?

    Can anyone tell me the benefits and drawbacks of an inboard jet vs. an outboard jet? I understand that the inboard takes up more room in the boat, however, from my understanding, you can get more power with an inboard. Is this the only benefit?

    With an outboard jet, is it more likely that the jet unit will get bashed on rocks and other obsticles more easily? It just seems that with an inboard jet, the unit is more protected, as some boats have the welded bars surrounding them (excuse my terminology, as I'm new to jet boating). It just seems that with an inboard, you may be able to go shallower and over more extreme obsticles.

    Any other input on one option vs. the other is appreciated!

  2. #2
    Member Dirtofak's Avatar
    Join Date
    Apr 2006
    Location
    Beaver Creek
    Posts
    2,267

    Default

    I have an outboard jet. The only thing that I can think of that sucks is that I cannot put a cab heater that uses the engine coolant. I don't have a big table to walk around in the back of the boat either. I use less fuel than my friends with inboards. There are alot of variables to compare apples with apples. HP, # of people or load, etc..... A boat needs to fit the intended purpose of its owner. I got the biggest motor that I could justify with my needs and fuel prices.

  3. #3

    Default outboard vs. inboard

    I went through the same process. I now have an older Wooldridge Classic with a 351 inboard engine. My take is that with the inboard you get a much heavier boat with less room inside that may burn more gas than a similar sized outboard equipped boat when not loaded. The flip side is, as you said, you get the heater and when you compare the two boats loaded down my guess is that the inboard will may have the advantage with regards to fuel burned per mile traveled. My boat burns around 9 gallons an hour at 3500 rpm with an average speed of 33 mph with fuel tanks full (80gal) and a couple adults with little gear. Load the boat up with hunting gear and add 75 gallons of extra fuel and its 9 gph at 3500 rpm but the average speed is down to around 26 mph. That's still not shabby for a boat that is a lot heavier than a comparable outboard model from the start. It really does come down to what your intended use is for the boat.

  4. #4
    Member alaskanmoosehunter's Avatar
    Join Date
    Apr 2007
    Location
    Next to my trashy neighbor
    Posts
    362

    Default I'm a outboard fan...With the exception of

    the Phantom sport Jon.

    Otherwise outboards are nicer, at least for me.

    I would not go as far as saying inboards have more power than outboards. You would be amazed what a honda 150hp jet can do vs. inboard 351 or simular.

    The best thing I like about a outboard is if you suck something in your foot (or grate) you just have to raise it up and remove it. Inboards have stomp grates that work good to remove obstructions, but if that doesn't fix the problem you might be in for a rude awakening.

    I also like outboard jets better because the boat is usually lighter and I don't always have to find deep water, if I want to stop the boat a get out to the shore. For instance I have taken my flatbottom 80 hp up rivers and seen a moose on the shore I just cut the motor and raise it up a few inches to keep out of the gravel and take care of the moose. The inboard with a big block powerplant ahead of me seen the moose and had to keep going cause if he would have came off step he would have been stuck for sure.

    Maybe I bias, but I feel outboards are more versatile....You could buy a lower unit (prop) for deeper water too.


    I'm not knockin' inboards when I freezin' my butt off on cold days though.

  5. #5
    Moderator stid2677's Avatar
    Join Date
    Apr 2006
    Location
    Fairbanks Area
    Posts
    7,274

    Default

    I went with the outboard, I used the money saved on fuel to stay warm with a small propane buddy heater. Those V-8s sounds nice, but not after 8 hours, with my Honda 150 even at WOT it is very quite. Fuel use is 4.5 GPH at 4000 RPM. Plus I switch from Prop to Jet.


    Steve

  6. #6
    Member Xerophobic's Avatar
    Join Date
    Nov 2007
    Location
    Calgary Alberta
    Posts
    85

    Default

    As a general rule OB jets make less power than inboard jets. (the biggest production Mercury jet OB is currently only the 60/40, Honda 105, Yamaha 115 -yes I am aware you can buy bigger aftermarket legs) For this reason they tend to be mounted on light boats constructed with this power restriction in mind. This is unimportant untill one enters inteded use into the equation.
    For extreme rough usage where bottom contact is likely/inevitable a lightweight hull is a generally a bad idea. add in lots of cargo into that "spacious" OB boat and you now have a heavy boat with lightweight construction, Im sure you can see where that is heading...
    You would also be correct in assuming the OB is more vulnerable to strikes being mounted as it is.

    Inboards come in a vast array of powers and weights. yes they take up more room in the boat but they also are well protected and tend to have far more forgiving pumps when it comes to injesting debris etc. It is a rare impact on a properly built boat which takes an inboard jet out of action entirely. There are many options before you're into a "gas guzzling V8 and berkeley pump"

    We have seen a dramatic decline in the OB market and while we still are a distributor for OB jet legs (and we stock parts)we no longer build a single hull for OB's. Whether that is due to the popularity of Mercury SJ's or the simple decline in factory made OB jets who's to say but it seems for our market anyway inboards are/have taken over.

    For me personally OB jets do not have the performance required to do what I want. They are certainly not cheap and for me far too vulnerable to damage from extreme boating(shut up Chris we're not THAT hard on boats lol) to me something like a Mercury Sportjet would be a far better bet to allow shallow water running in a tough little boat designed to take all the hits I can give it while being relatively easy on fuel and deadly reliable. Also SJ's are not that heavy when it comes time to push(which i see as inevitable) yet they make 240 hp which you certainly would have a hard time getting from a OB jet. Generally inboards are far less limiting in terms of what the boat will be capable of and will certainly haul cargo far better.

    I would have to say the biggest difference, if I had to narrow it down to one, would be the differences in how the hulls are constructed and thus the durability of the boats in question.

    For lighter duty river running or where bottom contact is very unlikely or completely avoidable they serve their purpose well

    Cheers

    p.s. I dont think ANYONE would even consider doing this with an OB jet...





    Skinny water addict

  7. #7
    Member
    Join Date
    Jun 2006
    Location
    Fairbanks
    Posts
    106

    Cool OB v IB

    Ruger-

    The physics of an outboard jet are limiting. An outboard jet has flow characteristics that limit it's thrust. You will get about the same thrust from a 225hp OB jet that you will from a 150hp OB jet. Consequently, putting a bigger OB motor on your boat (above 150hp) will not gain you much in the way of improved thrust at the nozzle. Additionally, efficiency is about 20% less vs. an inboard jet.
    I am a big fan of sprint boats as well and will compare them below.
    Check out Xerophobics sprint boat page, you will want one!

    There are advantages and disadvantages to both...of course!

    Examples:

    Several years ago I went way too far (140 miles) in way too little water up an unnamed interior river (you river experts or people that know this story can probably guess which one) in a 351 powered IB. The boat got me home, but not before I inflicted extensive damage to the hull.
    I'm happy I had that boat because of payload capability, but I also sacrificed increased boat weight.
    The sprint boat could NOT have carried the gas needed, but would've probably survived the terrain.
    An outboard might have made payload, but I would have ripped the motor off the transom 3/4 the way there.

    Cost is also a factor.
    An OB is EXPENSIVE, eats less gas but is less efficient at the nozzle.
    An IB engine is less expensive, eats more gas but is more efficient at the nozzle.

    Each has a purpose...so get 3 boats and be happy.

  8. #8

    Default

    I personaly like the inboards for what I use a boat for. For me I like the feeling that I can throw a rod or spin a crank bearing and run down to NAPA and get a new 350 long block fairly inexpensive compared to a new or rebuilt 4 stroke honda. I sure like the heat that the engine provides as well. One other thing to keep in mind if you plan on useing it in the Sound an inboard weighs more and will cut the chop better. With the intake for the pump located under the hull you also experiance less cavitation. Just my thoughts.

  9. #9
    Member
    Join Date
    Oct 2006
    Location
    Alaska
    Posts
    1,283

    Default

    Quote Originally Posted by Xerophobic View Post
    As a general rule OB jets make less power than inboard jets. (the biggest production Mercury jet OB is currently only the 60/40, Honda 105, Yamaha 115 -yes I am aware you can buy bigger aftermarket legs) For this reason they tend to be mounted on light boats constructed with this power restriction in mind. This is unimportant untill one enters inteded use into the equation.
    For extreme rough usage where bottom contact is likely/inevitable a lightweight hull is a generally a bad idea. add in lots of cargo into that "spacious" OB boat and you now have a heavy boat with lightweight construction, Im sure you can see where that is heading...
    You would also be correct in assuming the OB is more vulnerable to strikes being mounted as it is.

    Inboards come in a vast array of powers and weights. yes they take up more room in the boat but they also are well protected and tend to have far more forgiving pumps when it comes to injesting debris etc. It is a rare impact on a properly built boat which takes an inboard jet out of action entirely. There are many options before you're into a "gas guzzling V8 and berkeley pump"

    We have seen a dramatic decline in the OB market and while we still are a distributor for OB jet legs (and we stock parts)we no longer build a single hull for OB's. Whether that is due to the popularity of Mercury SJ's or the simple decline in factory made OB jets who's to say but it seems for our market anyway inboards are/have taken over.

    For me personally OB jets do not have the performance required to do what I want. They are certainly not cheap and for me far too vulnerable to damage from extreme boating(shut up Chris we're not THAT hard on boats lol) to me something like a Mercury Sportjet would be a far better bet to allow shallow water running in a tough little boat designed to take all the hits I can give it while being relatively easy on fuel and deadly reliable. Also SJ's are not that heavy when it comes time to push(which i see as inevitable) yet they make 240 hp which you certainly would have a hard time getting from a OB jet. Generally inboards are far less limiting in terms of what the boat will be capable of and will certainly haul cargo far better.

    I would have to say the biggest difference, if I had to narrow it down to one, would be the differences in how the hulls are constructed and thus the durability of the boats in question.

    For lighter duty river running or where bottom contact is very unlikely or completely avoidable they serve their purpose well

    Cheers

    p.s. I dont think ANYONE would even consider doing this with an OB jet...






    Do that with our outboard seaarks all the time.

    Its actually safer with an outboard I think - The engine kicks up so that it doesnt get damaged.

  10. #10
    Member
    Join Date
    Oct 2006
    Location
    Alaska
    Posts
    1,283

    Default

    Also - The reason for Engine manufactures not making as many outboard jet options anymore is because of EPA regulations they have had to pretty much move away from 2-strokes, and into 4-stroke technology.

    Most river runners want 2-Stroke outboards because of the hole-shot you get with a 2-stroke. They need that instant power to get on up out of the whole and on plane so they dont stick it right away. You wont get that with a 4-stroke. Plus you also have to deal with the added weight.


    Go run most of the watersheds in SE Alaska. I gurantee almost everyone is running an outboard jet.

  11. #11

    Default

    Quote Originally Posted by skinnyriver View Post
    Ruger-

    The physics of an outboard jet are limiting. An outboard jet has flow characteristics that limit it's thrust. You will get about the same thrust from a 225hp OB jet that you will from a 150hp OB jet. Consequently, putting a bigger OB motor on your boat (above 150hp) will not gain you much in the way of improved thrust at the nozzle. Additionally, efficiency is about 20% less vs. an inboard jet.
    I am a big fan of sprint boats as well and will compare them below.
    Check out Xerophobics sprint boat page, you will want one!

    There are advantages and disadvantages to both...of course!

    Examples:

    Several years ago I went way too far (140 miles) in way too little water up an unnamed interior river (you river experts or people that know this story can probably guess which one) in a 351 powered IB. The boat got me home, but not before I inflicted extensive damage to the hull.
    I'm happy I had that boat because of payload capability, but I also sacrificed increased boat weight.
    The sprint boat could NOT have carried the gas needed, but would've probably survived the terrain.
    An outboard might have made payload, but I would have ripped the motor off the transom 3/4 the way there.

    Cost is also a factor.
    An OB is EXPENSIVE, eats less gas but is less efficient at the nozzle.
    An IB engine is less expensive, eats more gas but is more efficient at the nozzle.

    Each has a purpose...so get 3 boats and be happy.

    Where can I find this "Xerophobics sprint boat page"?

  12. #12
    Member alaskanmoosehunter's Avatar
    Join Date
    Apr 2007
    Location
    Next to my trashy neighbor
    Posts
    362

    Default

    Quote Originally Posted by OneLunG View Post
    Do that with our outboard seaarks all the time.

    Its actually safer with an outboard I think - The engine kicks up so that it doesnt get damaged.

    I agree...My hunting buddys sea ark w/150 honda OB can go places only one could imagine and we have hit somethings in pure accident that would total other boats and it keeps goin with no problem.


    Some of these videos and pictures show boats doing amazing things that are "HARD" on boats. The fact is many of us aren't out doing this to our boats let alone afford to do this or even want to do these things to our boats.

    But, if I had a boat shop and sponsers I would be HARD on boats too.

  13. #13
    Member Xerophobic's Avatar
    Join Date
    Nov 2007
    Location
    Calgary Alberta
    Posts
    85

    Default

    Im sure that type of thing "can" be done in almost any boat. The real question is how many times can it be done before the boat suffers some form of damage?

    For myself personally an outboard powered jet is designed for extreme light weight and travellig with limited cargo. If you hunt/fish with one or two then it can be a very practical effective way to get into the shallows. If you plan to do alot of heavy rock bashing, hauling gear and really abusing your boat(and expecting it to take it) getting to those ultra hard to reach places I dont think one can compare with an inboard jet. You need a durable boat and a durable boat needs power to push it. Outboard jets are inherantly inefficient, even worse than a conventional jetdrive!

    The Mercury SJ's have not yet gone to four stroke platforms altho I suspect they will likely do so in the near future. For now the EPA has allowed them to continue with the Optimax series and while heavier than the previous 175/240 series are still light powerful packages.

    Its very hard to make generalizations about any boat but many 4 stroke packages can plane extremely quickly and that is usually more a function of pump type that whats spinning it. Id have to say again I think the main reason OB jets may plane so quickly is due to their lightweight

    I can't say why so many run OB jets in a given area but in more remote area's that can also often be due to whats available and generally accepted. What history and education is present on certain drive systems. There are alot of places our boats are not popular but where they should be popular. I can't see anyone prefering a lightweight hull after driving something like the Tomcat pictured once they have driven one, but if you never see one then you wont likely even know what they are capable of. Certainly in Alberta it would seem that OB jets are an entry level jetboat of sorts and there is certainly nothing wrong with that.
    We just have not seen enough business in that feild to continue to persue it

    Cheers
    Skinny water addict

  14. #14
    Member Xerophobic's Avatar
    Join Date
    Nov 2007
    Location
    Calgary Alberta
    Posts
    85

    Default

    Quote Originally Posted by alaskanmoosehunter View Post
    I agree...My hunting buddys sea ark w/150 honda OB can go places only one could imagine and we have hit somethings in pure accident that would total other boats and it keeps goin with no problem.


    Some of these videos and pictures show boats doing amazing things that are "HARD" on boats. The fact is many of us aren't out doing this to our boats let alone afford to do this or even want to do these things to our boats.

    But, if I had a boat shop and sponsers I would be HARD on boats too.
    Dont ya love it when you're typing a reply and another question pops up lol

    I think this raises another good point. Is it that you "don't want to" do this type of thing to your boat or do you realize to do this repeatedly WILL damage that boat and thus it becomes an unattractive prospect?

    Personally I believe one should have the durability and construction to handle anything you can throw at a boat so you do not have to hesitate or wonder if you boat will survive a given encounter. This is what true back country boating is to me. If you have to second guess your equipment and if it will get you back to the trailer then you may be missing out on some aspects of the great outdoors.

    We see very few boats return to us for damage caused by rough use. It happens now and again sure but we feel strongly that a boat built well can handle years and years of abuse and come back for more. Thats what we want to provide our customers and I sincerely hope thats what they apreciate when they speak of their Outlaw boats.

    Im uncomfortable commenting on another builders boats and so at this stage I wont lol

    Cheers
    Skinny water addict

  15. #15
    Member Xerophobic's Avatar
    Join Date
    Nov 2007
    Location
    Calgary Alberta
    Posts
    85

    Default

    Quote Originally Posted by Ruger01 View Post
    Where can I find this "Xerophobics sprint boat page"?
    Im not sure that "sprint" word is being used in the correct context. We have built "sprint" style boats in the past(and still can) but dont offer them as part of a standard lineup.

    I believe he may be actually refering to our 16 and 17 sport models and they appear on our web page. There are numerous video's of them in action on our media page and youtube as well.
    They run about 60 mph and with a 1/2" keel and steel skid plate are fast fun and very rugged. Ask Chris he has 2 in his "stable". They actually have our patented Steptec bottom which is quite different than your typical sprint style boat.

    Cheers
    Skinny water addict

  16. #16

    Default

    Quote Originally Posted by skinnyriver View Post
    Cost is also a factor.
    An OB is EXPENSIVE, eats less gas but is less efficient at the nozzle.
    An IB engine is less expensive, eats more gas but is more efficient at the nozzle.
    No question there are big, fuel thirsty inboards. But...The 200 Opti inboard Sport Jet offers 5 plus MPG when pushing a 2000 pound craft @ 30 MPH. Are there any outboard jets that can match it for static thrust & fuel efficiency?

  17. #17
    Member
    Join Date
    Oct 2006
    Location
    Alaska
    Posts
    1,283

    Default

    You say Outboard driven boats cant take a beating?

    I'd love to show you my seaark.

    I've hit huge rocks with it. I've sunk it from hitting rocks and it flipping.

    It still does not even have a CRACK on it anywhere.

    To say one is better over the other is impossible to do. It comes down to a preference a person has.

    I personally will never buy an inboard jet. That is just me. I've driven them, and I have yet to be sold on them.

    A decent sea-ark with a good engine and a jet will always be the way to go in my mind. They are one of the most durable boats I have ever riverboated in, and have earned my respect above all else.

  18. #18
    Member
    Join Date
    Oct 2006
    Location
    Alaska
    Posts
    1,283

    Default

    Quote Originally Posted by Kevin Turner View Post
    No question there are big, fuel thirsty inboards. But...The 200 Opti inboard Sport Jet offers 5 plus MPG when pushing a 2000 pound craft @ 30 MPH. Are there any outboard jets that can match it for static thrust & fuel efficiency?

    Even the Optimax outboards get great fuel efficiancy, they are one of the most fuel efficient outboards on the market right now (even over 4-strokes)

  19. #19
    Member Xerophobic's Avatar
    Join Date
    Nov 2007
    Location
    Calgary Alberta
    Posts
    85

    Default

    Quote Originally Posted by OneLunG View Post
    You say Outboard driven boats cant take a beating?

    I'd love to show you my seaark.

    I've hit huge rocks with it. I've sunk it from hitting rocks and it flipping.

    It still does not even have a CRACK on it anywhere.

    To say one is better over the other is impossible to do. It comes down to a preference a person has.

    I personally will never buy an inboard jet. That is just me. I've driven them, and I have yet to be sold on them.

    A decent sea-ark with a good engine and a jet will always be the way to go in my mind. They are one of the most durable boats I have ever riverboated in, and have earned my respect above all else.
    A comperable beating to an inboard jet? IMO no I dont believe they can.

    Again please do not misunderstand where I am coming from I just believe those who run inboard jets have higher performance expectations than those running OB jets, which is understandable. OB jets have their place and they "are what they are"

    I just dont think you can deny that there is no comparison to what a boat built like "this" will take in terms of abuse compared to a boat with a simple box stringered 0.125" or 0.1875" bottom

    Cheers

    Skinny water addict

  20. #20

    Default

    Quote Originally Posted by OneLunG View Post
    Even the Optimax outboards get great fuel efficiancy, they are one of the most fuel efficient outboards on the market right now (even over 4-strokes)
    No question the Opti power head is fuel stingy. The difference is in the pump designs.

    I've tested the 200 Opti SJ / 200 Opti OB Jet (140 @ the pump) / 250 Opti XS Ob Jet (175 @ the pump)
    The 200 Opti Sport Jet performed best in all categories.

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •