Compression problem 4-stroke 90

[Andre77]

I purchased a Mercury 4-stroke 90hp in 2002.

I used the motor not much more than 30 hours a year and have had it professionally serviced each year. I have always been extremely careful using it, and serviced it well (i.e. the dealer replaced the water pump at recommended intervals, I used only Mercury oil and filters, etc).

This spring, I had problems starting the motor. The dealer said that there was no compression in one of the cylinders, and very low compression in one of the others.

He installed a reconditionned head (BTW, it took two months to get the required "shims" because the dealer claims they have to be ordered from China because the head is manufactured by Yamaha (!).

The repairs cost me 1 700$.

My question : given that the motor has only 200-300 hours on it, what could have caused this compression problem so soon?

I would very much appreciate any information about this, such as recalls or frequently reported problems similar to mine with this motor. And any advice about how to avoid a repeat ...

 

[Dave1027]

Re: Compression problem 4-stroke 90

Probably overheated and warped the head. Maybe sucked up some debree clogging the cooling system. This is what can happen with boat motors and their open cooling systems

 

[starcraft1982]

Re: Compression problem 4-stroke 90

couldve overheated as stated,or,you clogged a carb through dirt or debris and ran the affected cylinders too lean.

 

[Andre77]

Re: Compression problem 4-stroke 90

Very much appreciate the input.

I suspect that the problem may be cooling system related. I am super careful about the cleansiness of the gas i put in.

We are on Lake St-clair where the water is very shallow. I anchor my boat in front of my house and it takes nearly 20 minutes to reach a depth of 5 feet where I can tilt the motor vertically.

During those twenty minutes, the motor is probably less than a foot off the bottom. So it must be sucking a lot of dirt and weeds as I head out. Also, to start it, I have to tilt it up because it won't start if it is at an angle. So for a few seconds, it is running with the foot extremely close, if not right on, the bottom. Don't know what to do about that though.

Maybe I should install a temperature gauge (if such a thing exists) that would warn me if the motor heats up?