Barn find with low compression, cheer me up

[cgodfrey]

Dug a late 50's 25hp out of a shed.

Didn't run when it was put away decades ago. $40 as is. So I rolled the dice.

Got it home on the stand, squirt of WD40 in each cylinder. Fingers crossed...

48lbs on each cylinder. At least it's even, but not what I was hoping for.
Really not excited about the prospect of opening up the powerhead.

What are my chances that once I get this motor refreshed and running, the compression's going to bounce back?

 

[nwcove]

Re: Barn find with low compression, cheer me up

you could try soaking it with seafoam, could be just stuck rings. but you need to come up with the right model year.....no 25hp built in the late 50's....none till 1969.

 

[HighTrim]

Re: Barn find with low compression, cheer me up

What is the model number?

Good news is that they are even. Not every gauge is accurate, nor the same. The big twins are also not the easiest to pull over effectively without compression relief.

I would maybe start by testing your gauge on a known motor. Or, try another one if a neighbour has one.

If still low, dont fret yet. The rings could be stuck due to carbon build up, or the head gasket may be shot. Either issue can be a relatively easy fix without much dissassembly.

Take the head off, dress it, then reinstall with a new gasket. Torque to spec, in the correct fashion. Let us know if you need help with any of this.

Then remove the bypass covers. Will the rings bounce when you push on them with a small screwdriver? If not, SeaFoam, or OMC Engine Tuner will help free them up.

Once you get it good enough to run, decarb the motor with a heavy dose and recheck compression.

Any pics?

 

[cgodfrey]

Re: Barn find with low compression, cheer me up

It's a '58 Wards Sea King 25.
I know.... this is the J/E forum... but since it's an OMC product, and virtually identical to a J/E 25 big twin, I feel it's more appropriate to post here than the "other" forum.

Anyway... $40, bought it from a Swing musician, who sold it to me in full hepcat attire (gelled pompadour hair, sunglasses, purple velvet tuxedo)

Got the hood off, got the flywheel off, immediately noticed the coil held together by glue.

 

[colbyt]

Re: Barn find with low compression, cheer me up

Hightrim gave you some really good advice. I will add one thing, don't waste any money on other parts until you get the compression up.

A head gasket is cheap and so is the bypass cover gasket.

I wasn't so lucky when I did this, the blown head gasket allowed a little water in and the rings were really stuck. I got them unstuck after a complete tear down. They came out in pieces with no piston damage. Some day I may put that OB back together.

 

[HighTrim]

Re: Barn find with low compression, cheer me up

Cool I have the same motor but in Buccanneer trim.

Hopefully the rings are not rusted stuck. As he said, you have to open her up to cure that. Carbon buildup would be what you are hoping for.

 

[cgodfrey]

Re: Barn find with low compression, cheer me up

Took the Head Gasket and bypass covers off. Rings are free and springy. Tops of pistons, domes and old plugs are filthy. Cylinder walls aren't as good as I'd hoped, but aren't awful. A few little scratches, but no big scuffs.

 

[HighTrim]

Re: Barn find with low compression, cheer me up

Doesnt look bad at all. Ive seen much worse!

How are the sides of the pistons from what you can see through the bypass holes when your spin the flywheel?

OMC Engine Tuner, or Sea Foam should clean the pistons right up.

Hopefully if you lap the head, and install a new gasket you will be good to go.

 

[cgodfrey]

Re: Barn find with low compression, cheer me up

What's the best way to use Seafoam as a cleaning agent in this case? Put it in a spray bottle, soak the carbon soot for x amount of time, and then take a brush to it?
Will a stiff wire brush damage the surface of the metal, or should i stick to a plastic brush?
I always thought heat, by virtue of a pre-warmed engine, was a key factor in Seafoam's effectiveness, but that won't be a factor here.

 

[bonz_d]

Re: Barn find with low compression, cheer me up

I also add not to worry too much by those compression numbers and the reason I say this is because it is very difficult to get good numbers on a big 2 cylinder like that using an manual pull start to turn it over. A lot of times they just don't turn fast enough or get enough revolutions to allow a good reading.

For now just use a nylon parts brush, the big round ones, then before you put the head back on you might want to wipe down the cylinders with an oily rag and turn ot over a few times to get some lube into the rings.

 

[HighTrim]

Re: Barn find with low compression, cheer me up

It is more effective while running, but will clean up the piston tops just fine. I switch back and forth between the OMC Engine Tuner and Seafoam. Both work well. Spray it on, then let it soak, wipe off the next day.

I have freed up rings by removing all the covers and soaking the carboned rings until they will bounce.

 

[nwcove]

Re: Barn find with low compression, cheer me up

did you ever get the sea king put back together???