Yanmar YSE8 Motor Problem

[Kelvin001]

Can anyone help... I've got an old YSE8 which black smokes and will not get to max rev's under load unless the bottom of my 27' sail boat is perfectly clean, good for getting me to keep her clean but here in OZ she gets slim on her within a couple of weeks. Do I need to change my exhaust riser or does the head need coming off and overhauld??

 

[Eeyore]

Welcome!

It could be a fuel problem.....black smoke? Check the injector first.

The engine is relatively easy to remove complete from the boat and rebuild at leisure in shed/workshop if the worst comes to the worst.

 

[PetiteFleur]

Firstly check the water injection elbow - but you'll have to remove it and check it on the bench, I had a similar problem on my Perkins a few years ago and after having the injection pump checked and new injectors, I found it was the elbow! It was an expensive error - I should have checked the elbow first as it was totally blocked, only a 10mm hole instead of 30mm!

 

[steve28]

is the boat new to you ?, has it always been this way. If it has then the props pitch could be wrong. If its something thats been getting worse steadily then i would say the head needs looking at.

 

[oldharry]

Three things - One: YSE8s are prone to black smoke anyway, to the extent that it is regarded as 'normal' when they are on heavy load (i.e struggling against wind and sea)

Two: If the engine is struggling to reach full revs anyway then the prop may be a bit oversize for the boat. An inch less pitch might resolve it.

Third: as suggested the exhaust elbow or engine may be carbon choked.

6-7hp is not a lot for a boat that size so the lump will be struggling anyway in anything less than perfect conditions. Here in cold wet windy UK 15 - 20 hp would be regarded as minimum to get a boat that size home safely.

 

[JAYEL]

The YSE 8 in my trapper 300 (about the same size as yours)will only take the boat up to it's hull design speed when it is super clean, after that it will smoke like crazy and lay down a carpet of black soot (unburnt fuel) on the water in the boats wake. I have a digital tacho on my boat and under perfect hull and weather conditions the engine will push the hull up to just 6 knots at about 2700 rpm. into a sea or headwind you are lucky to get the engine up to 2000 rpm before the smoke and soot starts. If it revs freely in neutral there is probably no problem. If its slugish in neutral it is most likely the exhaust elbow. I overhauled my engine two sesons back, New injector, Gasket set, Main bearing, Exhaust elbow and Fuel filter, for just over £300. Did the work myself, after soaking every nut and boltin WD40 for about a month.