1987 evinrude 90 hp

[EastFLguy]

I just purchased this boat. I believe it has been sitting for about 2 yrs....frozen steering controls, corosion etc. It starts fine with earmuffs but wont idle in the water. I had it out and when run full throtle....it bogs down. Im sure the carbs need cleaning. My main issue is that I did a compression check.....3 cylinders had 100 psi and one had only 50. Do I need a complete rebuild ? I really am frustrated and need some advise. Thanks

 

[racerone]

Remove the cylinder head.-----You may find a blown head gasket.------But these motors are famous for broken piston rings.-----If that is the case then it will need surgery accompanied by some $$$$ spent.

 

[Bosunsmate]

Dont stress, its not too expensive if you do it yourself. Its not hard to rebuild them if you can do just basic mechanical work such as changing a car filter then you have the attitude to do a rebuild and that the most important tool.
There are online manuals how to do it and plenty of advice here. Main thing is to do whats suggested in post two first

 

[emdsapmgr]

When you pull the head off the low compression side of the block, check to see if the top ring is cracked. If it is, you will see what appears to be small dents in the crown of the piston and the face of the head. A sure sign the ring let go. You'll be needing an overhaul and new ringsets and at least one new piston. Maybe a new head. Hopefully, your engine compression test before purchase indicated a problem and that you took that into account in the purchase price.

 

[EastFLguy]

Thanks for responding guys. I will pull the head and have ordered the manual for this engine. I have some mechanical experience but not with outboards. I actually thought 2 strokes had real valves...LOL. And emdsapmgr....I did the unthinkable and trusted the seller without doing a compression test. Im old enough to know better but I seen the center consol/ bimini top and went stupid.

 

[EastFLguy]

Update... I pulled off the head and Racerone got it right. A ring broke and chewed up the cylinder walls and head. I am pulling the powerhead and trying to find a local machine shop to maybe re-sleve the cylinder. Thanks to all for responding to my post. Maybe I can help someone else here in the future.