Opti Sport Jet Questions

[Bob the fisher]

Got a question for you Sport Jet fellas, (hopefully AKGravelpumper will advise as I hear you are the man)....when taking off the motor goes to 5600-5700 rpms, boat gets on step, kinda slugishly then the rpms drop to 5000-5200...why??? Does something need adjusting or did I break something already? Please help as I like 41-42 mph better than 35-36 mph....thanx and "fishon"...

 

[Dupont Spinner]

Sounds like an impeller problem or a slight blockage.

 

[Exactboats]

Take a long feeler gauge and slip it through the grate and check your blade clearance from the impeller housing. It sounds like your pump is slipping to get on step with those high rpm's. Once your on step the rpm's will drop. The only adjusting you can do is rebuild your impeller and install a ss wear ring to tighten up the clearances to 30 thou or less.

Claude:

 

[tjm]

I hope you don't mind me jumping in here Bob...Perhaps I can help clarify the problem...I have no idea what is causing your issue but maybe I can add a few tid bits to help you get a diagnosis...

I think the issue is basically the motor won't get to full RPM's when cruising...I don't know what would cause that...

I checked the impeller clearance and it is what you'd expect with 20 hours on the impeller, basically rather new looking with the standard sloppy clearance that comes standard with the pump from mercury....the stator did show that he was pumping a little bit of gravel...the little bit of over rev you reported could be from a little bit of wear on the impeller or even just junk you picked up from the river, but that wouldn't cause you to not get to full RPM's...

based on what your impeller and clearance looked like I'd rule out any issue related to that, hitting 5700 when stepping doesn't indicate a worn out impeller...perhaps a little bit worn, but certainly not worn out...

what is odd is that at full throttle you are only getting 5000 RPM's, hopefully someone will know what could cause that...the only thing I can think of is your exhaust is getting blocked as that would drop your R's a lot, but I highly doubt that is happening, especially when going forward...

I hope you get your issue fixed quickly, I know you've been enjoying the heck out of your new boat and summer is too short to be having motor issues...

 

[Buzz]

hmmm. It's like you're cavitating a bit at take off but not enough to prevent from running. The RPMs are getting me though. Does it feel or sound like you're cavitating when you first take off? Sluggish at 5600-5700? Something is missing. If the jet has no obstructions, I would check a few engine items. Confirm that the throttle cable is physically opening the throttle all the way. Also, spark plug wires do come loose. You'll definitely lose RPM. Sounds dumb but just check. I've seen it happen on the sport jet.

 

[pa18tony]

Had a simular problem with my outboard and it was the reverse linkage.

 

[pa18tony]

The engine would run up to full rpm out of the hole and then drop in rpm's the same as what yours is doing. The linkage was letting the reverse bucket drop into the jet flow causing the reudced rpm. Stumped me for a while.

 

[Bob the fisher]

Hey guys, I got a call from Mel this morning. It appears that Phantom and/or Mercury read my post (how frickin cool is that) anyway, he/they said that mercury reported that these motors (3 star rated) do not like negative back pressure from the exhuast. My rubber pipes go right into the water when idling and are barely above the water when moving. Was told to remove them and see if that works. Will do that tonite. Also, the new buckets are at marita, heading there in about 5 minutes to get mine. Going to Knik on Saturday to get me another King if anyone wants to join. Probably take a ride as well as my wife is finally going with...thanx for all your advise fellas and keep it coming....I'm trying to avoid as much down time on this puppy as possible..."fishon"

 

[kgrant]

I have an installation manual and it states:

IMPORTANT: When installing muffler assemblies, a 2.0 inch minimum distance beween bottom of muffler and water line must be kept. This minimum distance must be calculated with boat under its maximum load.

 

[Armed_alaskan]

First real problem

First real problem

Bob the fisher I need to see if my boat does the same thing, I haven't really looked to see what it does at take off, but will look as soon as wed (8th) thru Sat, I'll check the rpms.

I do know after the ranger helped me get back into the water I could not go faster then 4350 rpm and would get a loud beep due to cavatation. At the pull out I found eight+ rocks and small chunks of wood stuck in the grate.

I didn't even think about the stomp gate until driving to the pull out.

Old to soon and smart to late; I'm a green horn with a nice boat.

This was getting stuck for the first time on 4 Jun 11; Little Su 17.3 miles up river from the boat launch. Tried to turn around to fast and then to slow slid right up to the tough spot.
Had to call for help :think:a few phone calls and some advice from friends; I called the ranger on the river and he came up and helped me get it back into the water. This boat getting back into action was a tough job. :topjob:
Picture 059.jpg

 

[tjm]

armed alaskan...Glad you decide to take a U-turn and come chat a bit with me the other day...I'd be happy to meet up with you anytime to assist if you are experiencing issues with your boat...perhaps after work one evening at knik...

 

[Bob the fisher]

I was advised to remove the two rubber exhuast hoses that come off the back of the boat, I did and that sucker runs flat out @ 5400-5500 rpms. Runs like it should. Noticed an immediate result. If you have the pipes (rubber hoses) I would remove them asap. Also...the stompgrate is your freind...just an FYI..ha! ha! ...going to Knik this Saturday (bout 9am) if you want to go...."fishon"

Bob the fisher I need to see if my boat does the same thing, I haven't really looked to see what it does at take off, but will look as soon as wed (8th) thru Sat, I'll check the rpms.

I do know after the ranger helped me get back into the water I could not go faster then 4350 rpm and would get a loud beep due to cavatation. At the pull out I found eight+ rocks and small chunks of wood stuck in the grate.

I didn't even think about the stomp gate until driving to the pull out.

Old to soon and smart to late; I'm a green horn with a nice boat.

This was getting stuck for the first time on 4 Jun 11; Little Su 17.3 miles up river from the boat launch. Tried to turn around to fast and then to slow slid right up to the tough spot.
Had to call for help :think:a few phone calls and some advice from friends; I called the ranger on the river and he came up and helped me get it back into the water. This boat getting back into action was a tough job. :topjob:
Picture 059.jpg View attachment 49682

 

[Armed_alaskan]

tjm,,,going to a new area would be great, and every water patch for me has been new so far. Other than driving past the knik on the Glenn, is as close to it I've been. I can meet up, but don't know where the river launchs are at; as for time off, I have Wed-Sat off.

 

[Armed_alaskan]

Steep learning curve

Steep learning curve

I think my problem was (head space and timing) due to all the junk in the grate and not thinking "stomps the grate". I'm so new at the boating world I wasn't thinking *immediate action* was to clean out the grate. It’s got to be a little funny to the experts :lol: I believe that was my main issue and didn't even know it.

 

[Bob the fisher]

Ya it took me a bit to remember to stomp the grate as well. As for the boat launch at knik, you take the Knik river access, it is just north of the highway bridge going over the knik river...its not really a boat launch as we know it but it works just fine. Go to the end of the parking lot, far right side next to the bigger rocks and drop it off the edge...piece of cake man...maybe see you there saturday...."fishon"

 

[OzAK]

Answer me this

Answer me this

Hi Bob, glad you tracked down your problem, now let me toss this out. For those of you that were at the gathering, perhaps you got a look at the business end of my boat, but most maybe not. The question for all is this: If the rubber hoses you had on your boat caused all the problems, then why havn't I ever experienced any problems like you described? The attachments you see have been on my jetsled since just after the 10 hour break-in period with no apparent ill effects. They are completely submerged when idling and I presume because of the added backpressure this allows/produces the result of the engine actually warming up to where it shows 150* on the temp gauge. Crack the throttle a bit and the temp comes down to its "normal" below the lowest mark on the gauge, too cold to read anything. I've also experienced 0 RPM loss or anything else for that matter. The outlets are obviously parallel with the centerline of the craft but seem to be just barely submerged when on step. Perhaps thats the answer, the pipe outlets on yours were perpendicular to the C/L exhausting straight down into the water. The angle cut on mine doesn't hurt either, helps the water flow past the pipe outlet pull whatever exhaust is there out


of the pipe. Whatever it is, it also quieted the boat down a dB or 2. It's a quiet beast from behind especially, and helps it be a quieter boat overall. Stuff to make us scratch our heads. :think: What's next? As for the stomp grate, look into the remote activated stomp grate and lever like Fozzy and I have on our boats. It will allow you the luxury of opening the grate from the captains chair before you start and after you've pulled out from shore into deeper water. Don't forget to shut the motor down before "stomping" just to be cautious. I know of at least one incident that the grate was opened at idle with a grate full of rocks and one entered just wrong and locked the engine up from the rock digging into the liner and wedging the impeller. Bad day on the river then, had to beach the boat and either pull the back end off or chisel it out from up under the boat. Took awhile. Later, Oz

 

[Bob the fisher]

OzAk, my rubber pipes hung straight down about 2 inches below the boat so even when on step they were both in the water. I see your pix and like that setup. I have noticed that mine is a bit louder but It doesn't really bother me that much. It rips through the water now and I'm pretty happy with it. Also got the aftermarket bucket on there and that sucker backs up/pulls the boat right off the bank with the quickness. What a difference. As for the stomp grate, Fossy's setup is really kool but I don't know that I have the inginuity to design/build something like that. I usually give that job the the passenger right from the gitgo. Thanx for the advise though buddy and keep it coming...I really do appreciate all your help in learning about these jetboats..."fishon"

Hi Bob, glad you tracked down your problem, now let me toss this out. For those of you that were at the gathering, perhaps you got a look at the business end of my boat, but most maybe not. The question for all is this: If the rubber hoses you had on your boat caused all the problems, then why havn't I ever experienced any problems like you described? The attachments you see have been on my jetsled since just after the 10 hour break-in period with no apparent ill effects. They are completely submerged when idling and I presume because of the added backpressure this allows/produces the result of the engine actually warming up to where it shows 150* on the temp gauge. Crack the throttle a bit and the temp comes down to its "normal" below the lowest mark on the gauge, too cold to read anything. I've also experienced 0 RPM loss or anything else for that matter. The outlets are obviously parallel with the centerline of the craft but seem to be just barely submerged when on step. Perhaps thats the answer, the pipe outlets on yours were perpendicular to the C/L exhausting straight down into the water. The angle cut on mine doesn't hurt either, helps the water flow past the pipe outlet pull whatever exhaust is there out


View attachment 49771 of the pipe. Whatever it is, it also quieted the boat down a dB or 2. It's a quiet beast from behind especially, and helps it be a quieter boat overall. Stuff to make us scratch our heads. :think: What's next? View attachment 49770 As for the stomp grate, look into the remote activated stomp grate and lever like Fozzy and I have on our boats. It will allow you the luxury of opening the grate from the captains chair before you start and after you've pulled out from shore into deeper water. Don't forget to shut the motor down before "stomping" just to be cautious. I know of at least one incident that the grate was opened at idle with a grate full of rocks and one entered just wrong and locked the engine up from the rock digging into the liner and wedging the impeller. Bad day on the river then, had to beach the boat and either pull the back end off or chisel it out from up under the boat. Took awhile. Later, Oz

 

[William Brown]

Nice post. There have so many information which I need. Thanks for sharing this post.

 

[f0zzy2]

Hey Bob I think Compeaus might sells a kit for the Phantom/SJX. It's just a piece of pipe couple brackets and a cable. You might need a little longer cable is the only difference.

 

[Bob the fisher]

Is that right or are you yankin my chain buddy???.

Hey Bob I think Compeaus might sells a kit for the Phantom/SJX. It's just a piece of pipe couple brackets and a cable. You might need a little longer cable is the only difference.