I recently took my RIB out to N Wales and tried to launch, once the 1985 Suzuki DT65 started up I reversed out, and took off, within a few seconds I got on the plane, but then the problems started.. as soon as I turned the power dropped off leaving me with no revs. Then the engine packed in leaving me with choppy waves whacking me silly. I struggled back inland using my 3.5 auxiliary.
I thought it might have been the fact the engine wasn't warmed up before hitting choppy water - but this weekend (like a fool) I took the damned thing out again. It took a while to start, then I left it running for a good 10 mins before whizzing off with loads of power.. once again, I turned, instantly lost the power and it didn't come back!! It would idle and revs fine on idle, as soon as I hit the forward/reverse gear I would get about 2 knots from it before it died.
An epic followed which involved my auxiliary getting trashed (hit a submerged object) then I ended up manually paddling 200m against an undertow.
The Suzuki is firing on all cylinders, has slightly oily plugs, fuel bulb is full when engine switched off.. sounds great on idle, seems to rev fine in gear on flush muffs.
I read something about a valve on the forums - but I'm damned if I can find the thread.