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9.9 vs 15. (4 stroke Yamaha)

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  • 9.9 vs 15. (4 stroke Yamaha)

    Hey you guys. I am seriously considering eating crow.

    I discovered today that a 15 hp 4-stroke Yamaha weight within a pound or two of my 9.9 2 stroke Johnson. Furthermore, the Yamaha 9.9 weight LESS than my 2 stroke 9.9. Needless to say, I'm shocked. SHOCKED! I have 3 outboards for only one boat, and I'm considering selling two of them and buying one 4 stroke Yamaha to be the only outboard for my Grumman Sportboat.

    The price difference between the 9.9 and the 15 is about $300, $2700 and $3000 respectively, so that's not really an issue. With the 9.9, I'm dropping about 25 pounds, from 111# to 87# (that's about a 20% drop in weight) while keeping the same horsepower. With the 15, I'm gaining 50% more power for the same weight-the 9.9 two-stroke and the 15 four-stroke both weigh in at or close to 111#.

    Which is the better deal?

  • #2
    Keeping in mind of course the 9.9 2-stroke and the 15 4-stroke are very close in power output. I've always gone for max horsepower for an application and had a sportboat and it just got more unstable with speed...it just really isn't a planning hull. I always used a 4hp Yami 2-stroke but did try my evinrude 9.9 and it was a lot more powerful but became very unstable/uncomfortable.
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    • #3
      Originally posted by AK2AZ View Post
      Keeping in mind of course the 9.9 2-stroke and the 15 4-stroke are very close in power output. I've always gone for max horsepower for an application and had a sportboat and it just got more unstable with speed...it just really isn't a planning hull. I always used a 4hp Yami 2-stroke but did try my evinrude 9.9 and it was a lot more powerful but became very unstable/uncomfortable.
      Hmmmm. Yeah I don't really "plane" a canoe. I don't think it's possible-not truly planing, at least not with a traditional canoe hull. (A Gheenoe will do it.) Anyway, the 9.9 2-stroke pushes a load (me, a friend, his toddler son = 600 lbs not counting the engine and fuel) pretty good, if they're in the bow. Now, if it's just me in the back of an empty boat, then yeah, the bow just climbs higher and higher, and I get that with my 4 hp as well. I've maxed it out at 7mph with the 4 hp empty and 10mph with the 9.9 loaded.

      Curious....why would you think the older 9.9 2-stroke was close in power to the newer 15hp 4-stroke? In the old days (my 2 stroke is a 1975) the hp was measured at the power head; today, it's measured at the prop. In theory, I would think the older 9.9 was actually less than that at the prop and so even further apart from the modern 15.

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      • #4
        PS: I'm not so much looking for "speed and performance" as I am ability to go upstream loaded. There has been some discussion around here, and some members think a 9.9 might not be enough to go upstream loaded on rivers, such as the Tanana and Yukon, etc. Guess what I'm saying is I measure performance in miles per day, not miles per hour.

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        • #5
          Originally posted by FL2AK-Old Town View Post
          PS: I'm not so much looking for "speed and performance" as I am ability to go upstream loaded. There has been some discussion around here, and some members think a 9.9 might not be enough to go upstream loaded on rivers, such as the Tanana and Yukon, etc. Guess what I'm saying is I measure performance in miles per day, not miles per hour.
          I can speak from experience. I paddled upriver the other day. I had to get in close to shore and it was a bugger because of the bugs but it's doable.

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          • #6
            Originally posted by Yukon Cornelius View Post
            I can speak from experience. I paddled upriver the other day. I had to get in close to shore and it was a bugger because of the bugs but it's doable.
            I know what that's like. I spun a hub once going up the confluence of two rivers. I had to walk back cross-country while my friend took the Gheenoe down river to the nearest bridge.

            One thing that is different with this boat is that it rows really well. If the outboard could at least hold steady in the current, that would allow me to row back/upstream without fighting the current. Slow going though and physically exhausting.

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            • #7
              FL2AK-Old Towen a PM has been sent

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              • #8
                there is other 9.8 & 9.9 HP 4 cycle motors out there also in the 85 LB class I got one an still waiting to use it SID roud:

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                • #9
                  I wonder if we aren't up against hull speed in the Grumman Sport Boat when we get to about 10mph?

                  I had mine in the Tanana today at the foot of Chena Pump Road, maybe one river mile down from the Chena mouth. I was looking for how much weight I had to put in the bow to to get my trim "right" - I am looking for shallowest possible running draft first and best possible speed second.

                  I know I could just get a jet boat and run 40 mph in four inches of water, but I don't have $30k to play with. Total for Sport Boat, trailer and 5hp 4 cycle Honda I am in about $2000, maybe 2200. I can run 10mph in about 11 inches of water and I'll take it.

                  I found my shallowest overall draft -and top speed- at the same trim. Running upriver my Garmin Rhino was showing me 8.0 to 8.4 mph. Downstream I was seeing 11.0 to 11.4 with one glimpse of 12.2. I think that tells me my boat would be running 9.9mph in still water with no current, and the Tanana relatively close to shore today was running about 1.5mph.

                  My best trim was with 4 bags of tube sand, the 1/2 cubic foot ones lots of folks run in their truck beds in the wintertime. Felt like about 60 pounds each to me, so there is 240# in front of the bow seat, plus a 15# anchor, plus 10# of chain, plus my tool bag at close to 10#, I am calling it 275# in front of the front seat.

                  With my 190# self not in the boat, it trimmed out like the picture attached.

                  However, I did notice that if I moved to the middle seat I could get it to plow real real easy. I am going to come up with a kind of long tiller extension to see what happens if I sit in the middle and leave some sandbags on the shore.

                  EDIT:PS: If you decide to sell your 9.9 after I pay my property taxes I'd like a crack at it.
                  Attached Files

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                  • #10
                    Originally posted by swmn View Post
                    I wonder if we aren't up against hull speed in the Grumman Sport Boat when we get to about 10mph?

                    I had mine in the Tanana today at the foot of Chena Pump Road, maybe one river mile down from the Chena mouth. I was looking for how much weight I had to put in the bow to to get my trim "right" - I am looking for shallowest possible running draft first and best possible speed second.

                    I know I could just get a jet boat and run 40 mph in four inches of water, but I don't have $30k to play with. Total for Sport Boat, trailer and 5hp 4 cycle Honda I am in about $2000, maybe 2200. I can run 10mph in about 11 inches of water and I'll take it.

                    I found my shallowest overall draft -and top speed- at the same trim. Running upriver my Garmin Rhino was showing me 8.0 to 8.4 mph. Downstream I was seeing 11.0 to 11.4 with one glimpse of 12.2. I think that tells me my boat would be running 9.9mph in still water with no current, and the Tanana relatively close to shore today was running about 1.5mph.

                    My best trim was with 4 bags of tube sand, the 1/2 cubic foot ones lots of folks run in their truck beds in the wintertime. Felt like about 60 pounds each to me, so there is 240# in front of the bow seat, plus a 15# anchor, plus 10# of chain, plus my tool bag at close to 10#, I am calling it 275# in front of the front seat.

                    With my 190# self not in the boat, it trimmed out like the picture attached.

                    However, I did notice that if I moved to the middle seat I could get it to plow real real easy. I am going to come up with a kind of long tiller extension to see what happens if I sit in the middle and leave some sandbags on the shore.

                    EDIT:PS: If you decide to sell your 9.9 after I pay my property taxes I'd like a crack at it.
                    Scott do you mind sharing how you are going to do the extension?

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                    • #11
                      When I was a in my teens my dad had a 24' river boat and a 12 foot lake boat.

                      We were moving to the bush so we had alot of stuff to move.

                      He took the 12' lake boat and attached it to the front of the bigger boat and it worked great.

                      Then he went a little further and took the little lake boat and put a 25 hp jet on it ( reinforced the transom) and installed a stick with cables like a supercub in the front of it so he could get around pretty quick without the longer boat.

                      It worked pretty good but you want to keep your wits about you, lol. That thing was scary fast.

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                      • #12
                        from your photo, you do need to have a tiller extension on the tiller, that way you can stand up to stear, an see what is in front of you when going up a shallow stream , for the most part that is only in shallow water , you can move your gas tank forward with a long gas hose
                        { NAPA up to 25 FT works for me } , only problem you need to get the air out of the line every time you disconnect it front your rig
                        [ both ends ] that is not hard if you under stand what you are doing , SID roud:

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                        • #13
                          For the extension I am just going to get a piece of PVC pipe about the same ID as the OD of my tiller handle. Cut some slits in it and I'll probably use the same hose clamp that's on my existing tiller extension too short for this chore.

                          It won't be a permanent solution, I would need Inspector Gadget arms to steer the boat from the middle seat. But it will let me (hopefully) drop some weight out of the bow and maintain trim.

                          I have figured out how to work the lift from the middle seat if I go there, but having the motor on a working lift dramatically complicates setting up a whipstick to run the throttle, gear lever and tiller direction.

                          Current extension pic (about 18" long) attached. Link thingy re: whipstick: http://forums.outdoorsdirectory.com/...ler?highlight=
                          Attached Files

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                          • #14
                            Originally posted by swmn View Post
                            EDIT:PS: If you decide to sell your 9.9 after I pay my property taxes I'd like a crack at it.
                            Sure no sweat. It will be after hunting season, though.

                            BTW: it already has a factory made adapter on the grip (replaces the OMC rubber grip) for an extension tiller handle. All you need is a piece of metal conduit. Has a locking clip and everything.

                            Awesome looking boat,BTW

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                            • #15
                              Oh thanks. Black and green tigerstripe was the paint job I wanted in the first place, the spruce bough and fern prints are bonus. It was painted that way by the guy (a duck hunter) who owned it before the guy I bought it from. Gas tank is the same.

                              I went googling for "Sport Boat hull speed" but didn't find any scientifically informed discussion. It's going to have a good Froude number (though not as good as the canoe I sold to YC), http://en.wikipedia.org/wiki/Froude_number ; I am starting to suspect, given your results with a presumably healthy 9.9, that the hull speed for a GSB is right around 10mph.

                              If I am right that hull speed is 10mph the only reason we have to adjust our trim once we reach 10mph is to reduce our absolute draft. All we will get with more than 5hp is the ability to maintain 10mph with heavier loads.

                              Hmmmph.

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