Outboard Motors

[kevinheynes]

I have a Mercury 9.9 2 Stroke which is located in a well on my Jeanneau Tonic. It has been very recently serviced. It will not idle for more than a few moments and will peter out when changing from neutral to forward or reverse. One suggestion is that there is insufficient airflow at slow speeds or that the engine is taking in exhaust trapped in the well. Has anyone solved this problem?

 

[FullCircle]

Try doing it in a barrel of water. If it still stalls- the venting in your well is the issue.
If not, adjust the idle speed upward a bit and see if that cures it.

 

[kevinheynes]

Thanks. The engine does run well off the boat. What I'm interested in is how to improve the venting sufficiently given that the problem persists even if the hatch cover is kept open.

 

[wotayottie]

when I had a hunter with an outboard in a well, there was no way pou could run the engine with the locker lid down even though there was a vent into the stern.

I suppose you could try one of the engine vent fans.

 

[jeremyshaw]

Some thoughts:

1. If the exhaust is vented into the water, then presumably fumes are coming back up through the low pressure which will exist at the back of the boat. So closing the lid and providing a feed via a hose, scoop or blower (and an exit point) might do the trick.

2. If the exhaust is vented to air, is there some way to duct the exhaust away - I have to do that with a compressor I keep in a locker.

3. Hook up a length of hose of some sort directly to the air intake. That way it can only get clean air.

 

[RobinA]

I have a mercury 6hp 2 stroke (about 10 years old) which I used in a well last year on my Beneteau First 24. Initially we had the same problem.
In addition to the main exhaust which comes out through the prop (I think) there is an additional outlet on the back of the leg which vents into the well. I cannot remember why this is there - something to do with idling maybe when there is no flow of water.
Anyway we had to have a small brass spigot fitted to this outlet with a hose attached which then went out of the transom of the boat. Every thing then worked fine.
As far as I recall the 6hp is identical to the 9.9 with the exception of the carburettor.

 

[Hardley]

Agree with RobinA;
Anyway we had to have a small brass spigot fitted to this outlet with a hose attached which then went out of the transom of the boat. Every thing then worked fine.
Did this on my Yamaha 8, 15 years ago and now have no problems with fumes entering the cabin.
Same length of plastic pipe has survived all those years

 

[William_H]

I think the problem is likely to be more like just a poor performance when cold. ie does it have a choke and if so will it run faster /recover idle revs enough to get it all runnning in gear.
I reckon if the engine can be got running in gear to settle down then it is not a ventilation problem. albeit you says it runs ok off the boat.
good luck olewill

 

[lexi]

Try it with engine cowl off. Sometimes fumes can escape from exhaust below cowl and choke engine.

Alex