1988 Force 125 low compression in #1

[reelfishin]

I have a Force 125 which appears to have had very little use but was stored back in 1989/90. Its been sitting in a garage since then due to it's owners passing. I've known the motor since it was new, it most likely was only run a handful of times.
Anyhow, it's become my motor now, (along with the boat which I have since sold), I started with just some basic checks, I shot some penetrating oil into the cylinders the night before, changed the lower unit lube, and checked all connections. Upon checking compression I find the following top to bottom, 80-157-155-153. Adding some oil to the cylinders raises all of them by 10 to 15 psi. I borrowed a bore scope, and all 4 cylinders look good, no scoring and no signs of carbon. It was a freshwater motor owned by a guy in his late 70's when new. The fuel tank was still full, the gas actually didn't smell all that bad. The motor wasn't stored in any special way, it was just parked one weekend and left there till I got it last week. Cosmetically it looks new.
Is there anything on these besides stuck rings from sitting I should be aware of?
Should I go ahead and start it and recheck the compression after a good warm up?

The cylinders look mint now, I don't want to ruin a good block.

 

[maxum247]

Re: 1988 Force 125 low compression in #1

Pick up a can of (Quicksilver Power Tune Engine Cleaner) from your local Merc dealer, it is designed to remove combustion chamber deposites and free stuck piston rings. Follow the manufactures directions on can. max!

 

[bman1bpm]

Re: 1988 Force 125 low compression in #1

I'm sure you weren't planning to use the fuel in the tank, but just incase use fresh gas/oil mix!

 

[reelfishin]

Re: 1988 Force 125 low compression in #1

The fuel in the tank went with the boat, which I sold. I pulled the motor since the buyer didn't want it, and I didn't want the boat.

I have Sea Foam, but from what I can see in the cylinders, it's not carboned up at all, it looks pretty much like new. I suspect that the rings got rusty from non use and no lube after sitting untouched for so long.

I suppose there's some chance that just some heat in the engine may free up the rings but if their really bad or more than one are stuck, it could also damage the piston or cylinder.

I soaked the cylinders with penetrating oil for now, it's been too cold to mess with it outside here the past few days.

 

[kandil]

Re: 1988 Force 125 low compression in #1

did you try to start it? I would treat it as if it was new and add more oil to the mix have it run for a 10 min and check comparison.you said it went up 10 to 15 psi I hope that # 1 have the 15 Psi increase? you don't want the deferent more than 10 psi between Cly good luck.
BTW seafoam is good but I think you have to do it in the water

 

[moparman]

Re: 1988 Force 125 low compression in #1

a leak down test will show if its coming past the rings or else where. To do this you have to have a leak down gauge and put the motor on tdc. With the gauge pumped up with shop air ,and the hose from the gauge in the BAD cylinder zero the gauge and apply the shop air. the gauge will show the percentage of any leakage,and depending on where the air is leaking from,what is bad[rings ,piston,head gasket].

 

[Frank Acampora]

Re: 1988 Force 125 low compression in #1

80 PSI is not too low, or so low that it would indicate damaged cylinders. SO: given that, I would start the engine and run it with double oil for a while, after it heats up. If the fresh oil has not freed the rings THEN I would consider it time to try Seafoam.

Sometimes the aluminum piston will gall, wiping aluminum into the ring grooves and keeping the rings from expanding. This can happen without scoring the cylinder liner. No amount of Seafoam will correct this. I would also take off the bypass cover on the affected cylinder to see if I could see scoring of the piston. Unfortunately, this galling usually occurs on the exhaust side, but it's worth a try. Notice I did not say to remove the exhaust cover to look at the affected piston. You can try, but in all likelyhood, you will twist off a couple of bolts and that's a pain. And, the gaskets are expensive.

If the compression does not come up, you have the choice of running the engine like it is and accepting a loss of power with the possibility that after extended running, the rings MAY free up.

OR, you can remove the carb, manifold, and head. Push the piston and rod out, free the rings and re-install or replace the piston.

 

[reelfishin]

Re: 1988 Force 125 low compression in #1

80 PSI is not too low, or so low that it would indicate damaged cylinders. SO: given that, I would start the engine and run it with double oil for a while, after it heats up. If the fresh oil has not freed the rings THEN I would consider it time to try Seafoam.

Sometimes the aluminum piston will gall, wiping aluminum into the ring grooves and keeping the rings from expanding. This can happen without scoring the cylinder liner. No amount of Seafoam will correct this. I would also take off the bypass cover on the affected cylinder to see if I could see scoring of the piston. Unfortunately, this galling usually occurs on the exhaust side, but it's worth a try. Notice I did not say to remove the exhaust cover to look at the affected piston. You can try, but in all likelyhood, you will twist off a couple of bolts and that's a pain. And, the gaskets are expensive.

If the compression does not come up, you have the choice of running the engine like it is and accepting a loss of power with the possibility that after extended running, the rings MAY free up.

OR, you can remove the carb, manifold, and head. Push the piston and rod out, free the rings and re-install or replace the piston.

I don't think its a galled piston, chances are this just sat too long without being properly stored. That piston may have been all the way down or in front of the intake or exhaust ports which exposed it to some moisture or what ever.
I am leaning towards running it and seeing what happens. I think maybe once the aluminum piston expands a bit with heat, it may be fine. If not, I'll pull that rod and piston and free the rings.

 

[TexasBayFisher]

Re: 1988 Force 125 low compression in #1

Reelfishin, was compression restored after running the engine?

 

[reelfishin]

Re: 1988 Force 125 low compression in #1

I haven't bothered much with it yet, I sprayed the cylinders down real well with PB blaster, and let it sit on a stand in the garage. I've been busy with other projects and sold the boat that it was intended for.
Once the weather decides to cooperate and stay warm, I'll roll it out and get it running and then see what happens.