Need help - 1998 Speedster 787s, one engine dies at 3000-3500 rpm, 132/135 psi

[CaptM]

Hi guys,

Finally bough a 1998 Speedster with twin 787s which I love how they look!

Ran 43.2 kts GPS with rope around starboard impeller shaft

Anyway, Port engine was very hard to start and wouldn't stay at idle, also sounded very rough, like lots of metal sloppy noise to it, a little worse than starboard. 131/135 psi compression.

Starboard engine runs great 150/150 psi.

Trailer had SBT stickers, so I assume one (or both?) engine was SBT..

What I did is replaced the fuel filter on port engine with Yamaha larger unit (Local Seadoo dealership said this is what they use for replacement). Didn't mess with cheap automotive non original fuel filter on good running STBD engine.

All 4 carbs leaked, so all carbs were just rebuilt.
On a problematic port engine idle was raised so it will stay idling.

Tests showed both run ok (44 kts GPS with 1' waves)

But 1st time out after about 30 min ride and 60 min at anchor, trip back home - port is really hard to start (full throttle start) and then it will only start running and will only (slowly) accelerate to about 3000-3500-3800 rpm, when the rpm drops down slowly, if I pull the throttle back it catches and runs ok, if I keep giving it throttle it dies around 3500-4000 rpm.

Also what is new now that engine fails to be shut off by stop/start switch and keeps running and tach doesn't work?

Mechanic advise was to replace the engine, because with 131/135 psi things look bad..

What can I do? Replace Top end only? Any ideas on what is going on?

Other engine runs great..

Thank you!

 

[racerxxx]

Comp is getting really low on that, you could posibly do a top end....possibly. Did you replace the needle and seat when you rebuilt the carbs? What kits did you use.

 

[CaptM]

Was done by a mechanic, he said used full kit, everything was replaced.. not sure which one, will find out..

The question is how to check condition of bottom end and decide on doing top end only or full engine?
Also not sure why would it progress from running ok, to 3500 limit with no tach output/no stop?

 

[CaptM]

Is there any way to check the condition of the bearings without tearing it apart? Trying to decide top-end vs rebuild vs new engine..

Talked to a guy he says rebuild will cost me $2200 with "non Chinese" parts..

Other guys says for $1700 I can swap SBT with labor..

What you think?

 

[Summit154]

i work on my own boats i don't bring them to anyone, but i can check out some of the bottom end when i pull off the top end, you said it's sounds like theres metal in it, sounds like your starter is goin and i would suggest redoing the top end just for shits and giggles, but no there really isnt a way of checking if its damage unless you pull the jugs or carbs and the plate behind it off thats really the only other way i can think of checking for piston scarring or metal in the bottom end

 

[racerxxx]

I think I need to move to Florida with prices like that. I could under cut and make a killing installing engines.


If you want to check the crank and bearings out it has to come out of the cases, there is no way you can do it in the cases.

 

[snikwad003]

$1700 with sbt engine with labor? The guy I bought my boat from sed he spent $1600 on that exact set up. Should be the quickest option but I question sbt and their head milling, to me you would only lower compression to lower power because of cheap parts. My boat has 1 rebuilt 787 and one sbt 787, the rebuilt is 3-4 years older than the sbt and has 150&145 psi while the sbt has 135&130psi. Sbt has a good warranty and they are the quickest option out there so im not knocking them on that but 20 psi of compression lowered on purpose from what spec is is alot.