1996 150XP Offshore Bad Cylinder

[PilotPat24]

Hi Everyone,

I currently have a 1996 150 XP Offshore Mercury engine. It's a 25" shaft and it has been in saltwater for it's whole life.

I am very meticulous with this engine. It's has been flushed with fresh water after everytime it was used. I service the engine every year including fuel filters, gear oil, water pump, grease fittings, thermostats, spark plugs, power tune, etc.

At the end of last year (2006), when I was winterizing the engine, I decided to the a compression check. I had one weak cylinder. The one weak cylinder was at 70 psi while the others were at 120.

I then pulled of the head and noticed that cylinder is scored. All of the piston tops are in great shape and clean.

My questions is, what should I do with that cylinder? The engine still runs great!

Should I try to clean the cylinder with crocus cloth?

I was kinda thinking that since it's still running great, I should just put on 2 new head gaskets and go off on my way.

Any ideas or thought would be greatly appreciated.

Thanks,

Pat

 

[JUSTINTIME]

Re: 1996 150XP Offshore Bad Cylinder

how badly scored?
u could hone and put new rings, but that would be half a$$

 

[PilotPat24]

Re: 1996 150XP Offshore Bad Cylinder

Hi Everyone,

I currently have a 1996 150 XP Offshore Mercury engine. It's a 25" shaft and it has been in saltwater for it's whole life.

I am very meticulous with this engine. It's has been flushed with fresh water after everytime it was used. I service the engine every year including fuel filters, gear oil, water pump, grease fittings, thermostats, spark plugs, power tune, etc.

At the end of last year (2006), when I was winterizing the engine, I decided to the a compression check. I had one weak cylinder. The one weak cylinder was at 70 psi while the others were at 120.

I then pulled of the head and noticed that cylinder is scored. All of the piston tops are in great shape and clean.

My questions is, what should I do with that cylinder? The engine still runs great!

Should I try to clean the cylinder with crocus cloth?

I was kinda thinking that since it's still running great, I should just put on 2 new head gaskets and go off on my way.

Any ideas or thought would be greatly appreciated.

Thanks,

Pat

 

[PilotPat24]

Re: 1996 150XP Offshore Bad Cylinder

ll, the scores are bad enough to give the cylinder compression of 70psi. You can feel the scores with the tip of your fingernail.

To hone that one cylinder, you have to pull the powerhead off correct? or can you do it in place?

 

[andy6374]

Re: 1996 150XP Offshore Bad Cylinder

A good machine shop that deals in marine inboards and outboards will be able to tell you if you can get away with just honing or if you'll need to rebore.

More important is that you figure out the root cause of the cylinder scoring. Since it was only on one cylinder, I am willing to bet that you have a lean jet in the carb feeding that cylinder. When's the last time you had your carbs cleaned or rebuilt?

 

[PilotPat24]

Re: 1996 150XP Offshore Bad Cylinder

Actually, on the same side, the tip cylinder has much smaller score marks. I didn't pull off the other head yet to see if anything is going there.

I never toched the carbs since new since I've never had any fuel problems with the engine. I've had a Racor Fuel in use since new. The engine has been great since brand new.

The engine ran great right up to when I took the boat out of the water.

 

[PilotPat24]

Re: 1996 150XP Offshore Bad Cylinder

I also Power Tune (Carbon Cleaner) the engine every year before the boat come out of the water.

 

[andy6374]

Re: 1996 150XP Offshore Bad Cylinder

My point really was, if it was an overheating or oil injection problem that all cylinders would look bad.


11 years without a carb cleaning or fuel pump rebuild...I'm willing to bet a lean condition is the culprit.

You never want to be in a position where you NEED to rebuild your carbs or fuel pump, as this increases the odds of cylinder scoring. Although almost all of us don't clean carbs or rebuild fuel pumps until there is a sign of bogging. At the same time it is a good idea to do these sorts of things every 3 seasons or so for good measure, ya know preventative maintenance.

Can you post some pics of the cylinder damage?

Good luck and keep posting-
andy

 

[PilotPat24]

Re: 1996 150XP Offshore Bad Cylinder

I can post pictures. I'll take pictures of the cylinders tomorrow.

Pat

Doesen't the Power Tuning clean the carburators? I've done that every year since new.

 

[JUSTINTIME]

Re: 1996 150XP Offshore Bad Cylinder

if scoring is on exhaust side, it was running lean

 

[andy6374]

Re: 1996 150XP Offshore Bad Cylinder



Nope. This removes all the carbon buildup on your piston, rings and cylinders. Decarbing (not carb cleaning but ridding the engine of carbon deposits) is also a good preventative maintenance procedure and should be done yearly as you have.

To clean the carbs they need to be taken off the engine, disassembled, cleaned out with carb cleaner, dry and blown out with compressed air, and then reassembled with new gaskets. Gasket kits will run you about $8 per carb.