Yamaha 30 Problems

[Stuart M]

Posting this for a friend who has just joined Ribnet:

I have a Yamaha 30 DEOL 1996 6J8L 461498 which stalls when the controls are in neutral and once the engine warms up. I can run it at home and it will tick over using the override throttle. when I use the boat and move the controls to neutral it stalls. I can only restart it using the override controls but when I move these back to engage the drive controls it stalls. I have had it back to the Yamaha agent who assures me it is fixed!! Can anyone help or even send me a copy of the relevant pages from a workshop manuel

[Nos4r2]

Do a compression test on it. Sounds like the rings might be going-it's usual for them to play up when in the water but be fine out of the water when the compression drops.

[Stuart M]

Surely if the compression is poor then it'll effect the engine all the time?

Any ideas what the compression should be?

[Biggles]

I had a similar problem to this on my Yamaha 50 when I bought it second hand last year.
It was sorted by the dealer cleaning the carbs.
It used to cough splutter and conk out.
If I remember rightly when I took the engine out for its initial run I got about 1/2 a mile then I got the problems. It probably sucked some old crap up that had been sat around whilst the engine was in the shop.

I had some problems at the end of last year with sand in the fuel system but that didn't seem to be as bad. The sand came off my anchor which was stored next to the fuel tank. Its amazing where sand gets to.

Its just one of those things with engines and the sea I suppose. Lots of nasty saltwater and sand waiting to get everywhere.

[Nos4r2]

Originally Posted by Stuart M

Surely if the compression is poor then it'll effect the engine all the time?

No-when your engine is out of the water there's less backpressure in the exhaust. Increasing the backpressure increases the blowback past the rings, hence the stalling.

Originally Posted by Stuart M

Any ideas what the compression should be?

Compression should be over 100psi and within 15% max of each other. Within 10% is best.

[jwalker]

Originally Posted by Nos4r2

Increasing the backpressure increases the blowback past the rings, hence the stalling.

Does it?

[Matt]

Originally Posted by jwalker

Does it?

[Nos4r2]

Originally Posted by jwalker

Does it?

Yes-IF you've got low compression due to excessive bore wear/damage on a 2-stroke.