Cylinderhead....

[puddlesplasher]

Hi All,

The O/B is a Johnson 30hp. Recently overhauled and then after the second session the thing would take it's time in starting. Usually once in around every 10 attempts. When it runs it runs but when it wont start it wont start.

It was returned to the shop and the cylinderhead gasket was replaced as there was evidence of damage to the gasket, between the cylinders. Again it ran fine for 2 sessions and now its happened again.

So where do I go from here? In 18 months I have spent ?700 for servicing and major overhauling yet I am no further forward.

I have been told that it is likely that the cylinderhead needs skimmed. If so then who is there that you guys know that is reputable within the Glasgow, Scotland, UK area?

Also, at WOT I only get 10 knots approx for a 16 foot Microplus day cruiser with 2 people on board and all the fishing gear. Rev counter must be defective as it rests at 1000 and tops out at 2300.

Is this a prop problem?

So there we go, 2 problems and hopefully some advice.

Thanks,

Puddle.

 

[Cofe]

Re: Cylinderhead....

Welcome to IBoats!

The cylinder head needs to be made flat. You will continue to blow the gasket between the cylinders until you fix this problem.

Hard to start, and low RPM's indicate that you may be running on one cylinder. Check the spark and make sure it is good.

Also the carb and timing may not be in sync. A good mechanic should have fixed all these problems.

Do you plan on making these checks and repairs yourself?

 

[puddlesplasher]

Re: Cylinderhead....

The engine has only been used twice since a ?450 overhaul then I experienced the problems described. The lower spark-plug was rusted slightly hence the thought that the gasket had blown.

Cyl-head gasket was then replaced by the mechanic and the engine ran sweet as a nut. It started first time every time but the revs still appear to be lacking and without a working tacho it si hard to judge if there should be more power.

So, after the Cyl-head gasket was replaced (free of charge) the same problems with starting the O/B ocurred after its second outing.

Today I examined the plugs and they both have no water damage but the lower one was slightly brown looking (not rust) with some black soot deposits. They have been cleaned up and 2 new spark-plugs, properly gapped are waiting to be replaced if necessary.

The cyl-head was tightened slightly (1/8 of a turn per bolt) to seat the gasket as instructed by the mechanic.

Now I need to get the boat back in the water and see what happens.

 

[Cofe]

Re: Cylinderhead....

The fuel pump pulse suction is powered by the bottom cylinder. If the fuel pump diaphragm has a hole in it, fuel leaks into the bottom cylinder making a fuel rich condition.
Just a thought to check if you continue to have problems.

 

[puddlesplasher]

Re: Cylinderhead....

Hopefully it is not the fuel pump.

Many thanks though for taking the time and effort to assist me.

Ammendment: The O/B started first time, everytime today whilst out fishing. Plugs were cleaned and replaced.

Phewwwww *wipes brow*