'87 johnson 70 hp low comp on 1 cyl

[ultra353]

Looking at possibly buying this motor , owner says low comp on 1 cyl. Not sure how low or how big of a difference. Has tilt/trim and he's asking $325. Before I go look at it , R these decent motors, is it worth or walk away

 

[metriccrescentwrench]

There are several reasons for low compression. It could be nothing more than a head gasket, stuck rings, or something far more sinister. You might check it with a compression gauge to see just how low it is, but if the guy selling it is saying it's low it's probably very low.

At that price, imo, it's worth the gamble. If it's not an easy fix you could part it out and make money so long as the gearcase is good and the tilt/trim works. If it does turn out to be an easy fix that's a good engine.

 

[Silvertip]

Take a small LED flashlight with you. Remove the plugs and look into each cylinder as best you can. Excess carbon build up can generally be cleaned up with a good de-carbing using a product like SeaFoam. If the cylinder bores are all scratched, gouged, or otherwise damaged, the engine needs a rebuild. If the bores look clean and smooth, a set of rings may be all that's needed.

 

[ultra353]

K, thanks. Just bought a '85 alumacraft pro 17 for dirt cheap that's rated for 75 hp, it has a 50 hp merc on it now. Doesn't currently run, no spark, starter all rusted inside but turns over freely and seems to have good compression. My thinking is the 50 might be a bit small so I wanted to get a 70 or so on it. Get the 50 running and sell it in the spring to help with the cost of a bigger motor.

 

[racerone]

Is it the # 2 cylinder that is low ?---------If you are lucky it is just the head gasket.--------If you need to pay somebody to rebuild this motor then it will add up very quickly.

 

[ultra353]

I believe he said it is center cyl,says it runs but low compression . I haven't heard back for the numbers yet.

 

[racerone]

Well that would be # 2 and that is very common.----If you do the work yourself it may be worth it.-----If not then be prepared to spend big $$$$$$$$