1989 Force 125 with one weak cylinder

[dancewithme951]

Just acquired a 1989 Bayliner with 125HP Force. This boat had been sitting for at leat 2 years so I expected the worst (but got a sweet deal so why not?!). A number of relatively minor issues need to be addressed but first attempt at starting and the motor would barely crank with fresh battery...starter checked out fine I removed all 4 plugs and poured about 1/4 cup of Seafoam into all 4 cylinders and let that sit overnight. The next day, with all plugs reinstalled, water hooked to lower unit with ear muffs, she cranked right up and easily started. I was amazed! It ran surprisingly well but with occasional miss. Once sufficiently warmed I did a compression test, screw in teter and with throttle wide open. All cylinders tested out at 140 PSI but one - not sure the # but third one down from the top - which was 80 PSI...YIKES! My question for any takers: is there a possible cylinder specific quick fix for that one cylinder? Cannot afford to have engine rebuilt. Decarbonization perhaps? Any advice is appreciated.

 

[gregmsr]

Re: 1989 Force 125 with one weak cylinder

Did the previous owner tell you anything about the motor; "It ran good when I parked it"?
Setting 2 years may just have a stuck compression ring. I would dump more Seafoam in it, run it a little, more Seafoam. It may de carb itself and free up the rings.
No luck with this? Then pull the head and check out the condition of rings, cylinder walls, and piston in that cylinder compared to the other four.
Sounds like you have something to work with and you'll find great help here.

 

[gregmsr]

Re: 1989 Force 125 with one weak cylinder

Or rather, other three cylinders.

 

[hmantractors]

Re: 1989 Force 125 with one weak cylinder

I will bet a broke ring or it seized lightly and gouged the cylinder. Hope you get lucky. Carbon build up is not going to cause low compression.

 

[gregmsr]

Re: 1989 Force 125 with one weak cylinder

I wouldn't worry about the fuel lines. When the engine is cold, take out all the spark plugs and turn the engine over a couple times. Hook up your gauge and turn the engine over so the cylinder compresses three or four times (as long as you do them all the same), take & record your reading and watch to make sure your gauge is holding at pressure. ( some leak back thus effecting your reading, if you find yours is leaking, use a little WD-40 on the release valve until it holds pressure) Move on until all cylinders are read and recorded. Put it back together and run it up to operating temperature, and repeat the process. The hope is that all cylinders are within 10-15% of each other. (A 5 or 10 pound difference is nice, but if a high cylinder was 130, a low of 110 is acceptable) If not then the troubleshooting begins, worn rings, head gasket, etc....if an engine has been sitting a while, it is possible rings are stuck, giving a low reading, sometimes running up to temp a few times or decarbing may free them up. In your situation I would suspect/hope your gauge is leaking back.

What he said....

 

[dancewithme951]

Re: 1989 Force 125 with one weak cylinder

Thanks for all yor feedback. I'll apply a few more rounds of seafoam as suggested and see if I get improvement. I'd love to just head over to my nearby lake a run her a bit which may alone help. But I also need to replace the water pump and awaiting parts. Got a trim pump to replace as well...gotta love it!! Thanks again!

 

[dancewithme951]

Re: 1989 Force 125 with one weak cylinder

Oh, BTW: on the possibility of a blown head gasket, is that likely with only one cylinder involved? I read somewhere that when two adjacent cylinders experience abnormally low compression compared to the others that head gasket is more likely...your thoughts?

 

[Jiggz]

Re: 1989 Force 125 with one weak cylinder

At this point of your troubleshooting, your next best move is to remove the head and visually inspect the affected cylinder and head gasket. If there is scoring, the next move is to remove the piston. Search this forum on how to remove the piston without disassembling the engine block but through the intake side. Post pics of the cylinder if there is any scoring and also the piston for proper diagnosis.

 

[jerryjerry05]

Re: 1989 Force 125 with one weak cylinder

Got a small flash light?
Shine it in the hole and see if there is any damage to the piston.
Carbon'd rings WILL drop the compression.
When I first bought my boat the oil was tcw-1 and not good for the motor.
Went fishing and tried to start the motors,one started right up and the other just wouldn't go.
Took it home and did a compression test.1 cylinder was at 80#
Took it apart and found the rings stuck solid with carbon.
No damage to the cylinder or piston.
I like to use Mercury's power Tune or OMC's Engine Tuner.
Never had much luck with Seafoam.
That said, DON"T run it as any running with a stuck ring could do some damage.
Take the head off and check.
The #3 down also runs the fuel pump make sure the diaphragm isin't bad and flooding the cylinder.
Blowing a piston can be caused by:a carb not set right,or the recirc system clogged,or the timing being off,or the exhaust chest full of sand making it overheat.
Fill out the profile,you might be close to someone who can help.
Just remember if you run it like this,your gonna do a lot more damage and possibly ruin it beoynd repair.
If your lucky and it's just stuck rings,then it's not that expensive or that hard to fix.

 

[dancewithme951]

Re: 1989 Force 125 with one weak cylinder

Very sage advice...thanks. Particularly interisting what you said about my weak cylinder - #3 down - being the one pulling vacuum for the fuel pump. Despite it's lower compression, it seems to running the fuel pump satisfactorily - at least in the limited number of minutes I've run it - in that it runs nicely at least at idle. I do plan to pull the head once I order a replacement head gasket. I need to replace the water pump first as there's no telltale coming out the exhaust and i found the thermostat was faulty (replacing it as well).

And thanks for the prod to complete my profile info...doing that this very minutr!

 

[dancewithme951]

Re: 1989 Force 125 with one weak cylinder

Found the likely cause for low compression in cylinder 3. Removed the head and there are small metal fragments welded to the top of the piston, I prsume from a ring as it dstroyed itself. The good news - I think - is that the cylinder wall is as smooth as silk. I saw a post recently suggesting there was a way to replace a single piston/rings without doing a complete overhaul. I cannot let this recently acquired motor become a money pit - I haven't even had it on the water yet - so can't afford a complete shop overhaul. And I don't think I'm skilled enough to attempt an overhaul on my own. Any help on the one only piston/rings method? And BTW: the head gasket looks completely intact so that possible cause for the low #3 compression is ruled out.

 

[Justinde]

Re: 1989 Force 125 with one weak cylinder

If you can put on a shirt, you can fix one of these engines, especially with help from the guru's here. Plenty of pics, and the guys will be able to walk you through any repair......

GO FOR IT

 

[Jiggz]

Re: 1989 Force 125 with one weak cylinder

You will need to post a pic of the cylinder and also of the metal parts found. And then the next move is to search this forum for "Piston Replacement". There is one old thread that actually shows you the step by step procedure on how to replace a piston without having to disassemble the block.

 

[hmantractors]

Re: 1989 Force 125 with one weak cylinder

I was afraid it might have a broken ring. The rings, the top ring is very thin. I thought the rings would be more like 2 stroke motor cycle rings. But is not the case. My Force 70 had one good cylinder out of three. Found a very good 75 power head and put that on. If the weather will ever break will hit the water. If you can get the parts, you can repair the bad cylinder yourself. Just make sure you get all the needle bearings back in both ends of the rod. Good luck.

 

[dancewithme951]

Re: 1989 Force 125 with one weak cylinder

I found the post on single piston replacement and it seems pretty straightforward. And I found some nice looking pistons already attached to the rod on Ebay so then I won't need to deal with the special tool procedure of attaching the rod to the piston. There's very little damage to the head in that one cylinder so I think I'll just clean it up and deal strictly with the piston replacement. I'll post an update later. Thanks all for hints, advice...I may need more as things progress. I'm actually love the learning process. Just finished a Mercarb rebuild on a 1988 4.3L Mercruiser on a Celebrity 180 Bowrider. She purrs like a kitten now! And I also just replaced the water pump on my Force outboard. Apart from the awkwardness of getting the lower end back on (shaft/spline alignment while also trying to thread that damn shift through that tiny hole at the same time while basically sitting on the ground) that went well. On the Force I still have the new tilt/trim motor to install (and HOPEFULLY not find out cylinders need rebuilding...a-r-r-g-h). Hey, I'm having a good time! Hell, the more I read - and talk to you guys - I might even man up and opt to split the head and service all cylinders...we'll see!

Your worst day on the water is better than your best day at the office!!

 

[jerryjerry05]

Re: 1989 Force 125 with one weak cylinder

I have a piston and connecting rod that I'll give you for postage.
As long as you use a new head gasket and remove the recirc system and clean it.
One of the biggest thing in a complete rebuild is making sure the pins for the crank bearings aren't missed or mashed.
The gasket set can be found for as low as $60(last one I bought) look around.
Sent U a PM

 

[dancewithme951]

Re: 1989 Force 125 with one weak cylinder

Hey thanks. I responded to your PM.

 

[chestypuller]

Heck ill take the piston if he dont want it.

 

[jerryjerry05]

Chesty, you need a piston for a repair?
If so? What motor?