Problems with a '88 90hp; UPDATED

[Charlie in TX]

This motor has been on this boat and in the family since new. This problem is new. It is not running on all cylinders. By looking at the new plugs, the port cylinders are amiss.

First, the compression test. Port/upper - 60psi, P/l - 127, S/u - 137 and S/l - 132. For some reason there is water blowing out the 2 port during the test.

I tried to pull the head. One of the bolt heads stripped, it is too rusted. I have to get some different tools after it. I will have it off tomorrow.

Question, what would cause these combination of problems? Were should I be looking?

 

[Daviet]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

I would inspect the head gasket and see if it is blown.

 

[Charlie in TX]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

I hope to get that done in the morning.

 

[Daviet]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

Let us know what you find.

 

[Charlie in TX]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

Ok, the head is off. The gasket was blown on the top cylinder. It was intact on the lower. Both intake ports were loaded with water. I can understand water in the top cylinder, why the lower intake port? Are the 2 connected internally in the crankcase? Is water coming in to the top cylinder, into its intake port, thru the main bearing and into the lowers intake port?

What next? Clean gasket surface, reassemble, see if it holds?

 

[Daviet]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

You found the major problem, could have had a minor leak in the bottom cylinder.
You are correct, clean everthing up. Make sure the head is flat, install a new head gasket and torque to proper spec. Run the engine till it warms up, let it cool down and retorque the head gasket.

 

[Charlie in TX]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

What are the chances it has been running on 3 cylinders for a while? The top piston has a few oxide spots and the head has very little carbon build up.

Whats the proper torque? 25-35 ft-lbs?

 

[Daviet]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

It doesn't take long for water to wash a cylinder clean.
I don't have a manual for your engine in front of me, so I am not sure of the torque for your head gasket, I am sure someone will chime in with the proper torque for you.

 

[boobie]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

18-20 ft lbs. Start in the center and work your way out in a spirial pattern taking them in steps to the final torque. Start mtr, let warm up good and stop and let cool off. Then re-torque again. Check after 20 hrs.

 

[Charlie in TX]

Re: Problems with a '88 90hp

Re: Problems with a '88 90hp

Seems to be fixed. Finally got the head back on. The 60 psi cylinder is back up to 125 psi.

Upon further inspection, I see more signs the gasket had been blown for a while. The lower piston (with 127 psi) had nice sharp machined edges. The top piston (were it was blown) was eroded and looked like a raw casting compared to the lower. Hope it holds together for another 20 years or so.