Just bought 2 1997 Honda 90hp outboards got a few ?????

[adm1476]

I bought these 2 motors as parts motors. They are complete except for 1 missing starter. I did a compression test on both today, Not good news! I was hoping to make a good engine from both of these. However the compression in both of them is not good. I don't know what the specs are supposed to be but here is what I got. I know they are all supposed to be close. First engine had 110psi on top 118 next one down 125psi on 3rd one down, and 150psi on the bottom. Plugs were black as night. It also had signs of moisture inside the oil pan. I noticed this when I removed the starter to put on the other engine for testing. Engine #2 showed no signs of water in oil pan. Installed starter. top cylinder had about 70psi, next one had about 68psi, next one had 50psi and the bottom one has about 24psi. Plugs looked like new. LOL Ok so here are the questions??? Is there something simple that can cause this bad compression? If not is it worth doing some type of rebuild on one of them? Or should I just do what I did and resell them for parts to recoup my funds? Both lower units seem to be fine both stainless props are like new.

 

[AGENT 37]

Those are pretty rough sounding compression numbers. All the four strokes I have had have been over 150psi compression and matched within about 5 to 8 psi. Boring out and installing oversize pistons and rings are what's generally needed for those kind of results. An engine with water in the oil sump would also probably need bearings replaced, crankshaft overhauled and a significant amount of work on the cylinder head. Kinda sounds like you might have some good lower units and tilt trim assemblies to sell for parts. I personally wouldn't touch them in the condition you have described.

 

[adm1476]

That is kind if what I figured. Just a note which probably won't make much difference. When i did the compression tests on these motors they were laying on the ground, and i was using my battery charger and a screw driver to jump the starter to make it wind over. But bad is still bad. LOL Anyone want to buy 2 1997 Honds 90 4 stroke outboards complete for parts!!!

 

[hondam]

Just making sure you tested the compression properly. When doing a compression test on those motors the throttle needs to be at WOT, if you did not do that those numbers do not mean anything. This is tricky to do and is why i normally do a leak down test instead, its easier to do and produce more accurate results. Also the leak down test will give you an indication of what is going on internally, You can listen for the escaping air and determine what is actually wrong. For example if you hear the air coming out the carburators you have a leaking intake valve, out the prop the exhaust valves, the dipstick bad rings.

Compression tests are completely different on Hondas. Honda actually specifies a compression on those motors of 213psi +/- 14psi. And when testing the compression you have to make sure that the engine is spinning at least 300rpms.

To do the compression test at WOT, first remove the propeller, take the gear shift handle and put it in forward and advance it to WOT. Then get a starter button and hook it directly to the starter solenoid which bypasses the neutral safety switch.