Force 125 (1987) Cylinder Help

[grininmonkey]

I had a much lower compression on the #4 cylinder than the rest which was 135lbs and the rest where very close to 145, after cleaning carbs and everything else I could do on the easy and cheap, I still had poor (warm) idle and cutting off issue. So I decided to pull the cylinder head off.

Attached shows the cylinders which all look to be the same except #4 which appears to have a different bevel, the build up feels like metal, I can not scrape it with my finger nails (solid).

Is it a bad cylinder?
Is it suppose to be shaped different?

The picture with the cylinder that has a "B" engraved is the same on #1,2 and 3, #4 has "EXT" engraged?

Please advise!

 

[pnwboat]

Re: Force 125 (1987) Cylinder Help

What you see in #4 cylinder is a piston that was overheated. The crown of the piston has actually started to melt. That's why it has that rounded look to it. Most likely either from a lean fuel condition, or spark detonation due to timing too far advanced....or maybe something else. Need to take a look at your carbs, especially the lower carb. Also check the timing.

The markings on #4 piston are EXH, meaning exhaust and the little doohickey is an arrow indicating which way the piston should be oriented. The arrow should be pointing towards the exhaust ports. Looks like #4 piston may have been replaced.

 

[Jiggz]

Re: Force 125 (1987) Cylinder Help

There seems to be a sign of water intrusion on #4 caused by either a broken head gasket or improperly torqued head bolts causing overheating (steam, thus reducing lubrication). The pittings indicate it has been going on for awhile. And also the #4 piston seems to be of different maker. The "EXH" with the "< " indicates the required orientation of the piston when installed showing which side is to face the exhaust. I believe you will be better off replacing the piston, de-glazing the cylinder and then ordering the right size piston and rings. There are "fleet admirals" in here who will have better assessment but most likely will also recommend replacing the piston and rings at the least.

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

So I do need to replace #4 right?

I just bought the boat a month ago and have been working on the idle cut off issue since then. Before and after cleaning both carbs it was the bottom carb which had the best idle screw adjustment response. The top adjustment can be barely observed just by sound, which was making me wonder about the top, but it appears its fine and there may be an issue with the bottom carb or the reeds?

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

That makes perfect sense now. When I fist got the boat and had the cowl off I spotted water spitting up from the water exhaust boot and quickly replaced it. It had a small rip near the clamp.

Little 5 dollar rubber boot damaged the piston... geezz :-(

 

[Jiggz]

Re: Force 125 (1987) Cylinder Help

The bottom carb feeds both #4 and #3 cylinders. From the look of the #3 cylinder, the idle mixture setting seems to be fine. What is happening with #4 cylinder seems to be confined to that cylinder. And my personal assessment as previously mentioned is water leaking into the cylinder creating steam during combustion, reducing lubrication and eventually overheating. You might also want to investigate further on the source of water leak, i.e. crack cylinder or warped head. Either way, I would recommend piston and ring replacement which would also require at least de-glazing the cylinder.

 

[Jiggz]

Re: Force 125 (1987) Cylinder Help

That makes perfect sense now. When I fist got the boat and had the cowl off I spotted water spitting up from the water exhaust boot and quickly replaced it. It has a small rip near the clamp.

Little 5 dollar rubber boot damaged the piston... geezz :-(

I doubt the water leak came from the torn exhaust relief boot. Anyways, if you search this forum using "piston replacement" you will find detailed info on how to do it and the approximate cost and time required.

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

I found some good threads on replacing a cylinder, but I really worry about the process of removing/replacing the rod clamp and bearing cage threw the vertical reed ports. I really don't have an easy/good way to completely remove the powerhead, so I'm wondering if it is possible for me to just remove the crankcase cover, replace the cylinder and slap it back together?

From what I can see, looking around a bit, it does seem doable, I just don't know if I would be setting myself up for more headache?

 

[pnwboat]

Re: Force 125 (1987) Cylinder Help

When you say crankcase cover, if you are referring to the part of the block that the carburetors sit on, then no. You have to remove the powerhead from the leg to get the split the block open to gain access to the rod bolts to replace the piston.

 

[jerryjerry05]

Re: Force 125 (1987) Cylinder Help

FrankA changes the pistons without taking it all apart.
Somehow he goes through the reeds openings and works on it that way.
Like Jiggz says the exhaust bellows leaking wouldn't affect the piston like that.
It would contribute to poor idle as the exhaust gases get up in the cowl.
If the carbs set and 1 piston's burning right then it's probbly ok.
The reason could be the recirc system clogged,bad reeds,sucking air somewhere ETC!!!

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

That makes sense, more and more it seems I would be better off if I took the powerhead off and gave it a good inspection while replacing the piston. I do not have a hoist or anything to pull the motor so Im worried about going down that path. If I remove as much as I can, how much weight would I be dealing with?

I also noticed the gasket for the transfer port cover just above the fuel pump was sticking out much further on one side than any other, there is also a lot of oily build up in the area, not dirty but just a layer of film or wetness in the area.

 

[pnwboat]

Re: Force 125 (1987) Cylinder Help

The whole motor weights about 300LBS. Power head itself probably weighs 150LBS - 180LBS range. Kind of awkward to handle, unless you are up high enough, but not that bad. I know guys that have constructed a simple gantry out of 2 X 4 lumber that worked just fine.

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

Any suggestions on a good way to strap or hook up the motor. I have a come-along that I use to lift the hard top off of my jeep, which I route the cable using pulleys clipped into some eye bolts in the doorway of my garage. This rigging might handle 180lbs?

Thanks for all quick replies and knowledge, it's a great experience so far in this forum!

 

[pnwboat]

Re: Force 125 (1987) Cylinder Help

I just take a lifting strap or rope and look for some spots on the block to wrap it around. The hardest part of getting the power head off is separating it from the leg once all the bolts/nuts are loosened. The factory uses some pretty tough Silicone RTV between the adapter plate (which is bolted to the block) and the lower leg. Getting the two apart can be tough sometimes. Just be sure you pry between the adapter plate and the leg, and not the adapter plate and the block. May also have to take a single edge razor blade and slide in between the plate and leg to cut through the RTV sealant. Once it starts to come loose, it's a breeze. Of course, you have to remove the wiring harness and fuel line, battery cables etc. first.

 

[Jiggz]

Re: Force 125 (1987) Cylinder Help

I found some good threads on replacing a cylinder, but I really worry about the process of removing/replacing the rod clamp and bearing cage threw the vertical reed ports. I really don't have an easy/good way to completely remove the powerhead, so I'm wondering if it is possible for me to just remove the crankcase cover, replace the cylinder and slap it back together?

From what I can see, looking around a bit, it does seem doable, I just don't know if I would be setting myself up for more headache?

Remember for now it is about replacing the piston and rings and not the cylinder. I understand it is harder to do the bottom (#4) but it is still doable to do it through the intake manifold (where #2 carb is mounted). By removing the piston , then you can do a full visual of the cylinder to see if there is a crack or damage to it. From there you will decide if it only requires piston & ring replacement and for sure a new head gasket. Take a digital camera with you and take a lot of pics while disassembly so you have a good reference when putting it back. The rod caps require a 12-pt 1/4" socket to remove and install. After disassembly then order the parts and gaskets required.

 

[jasonbailey]

Re: Force 125 (1987) Cylinder Help

Remember for now it is about replacing the piston and rings and not the cylinder. I understand it is harder to do the bottom (#4) but it is still doable to do it through the intake manifold (where #2 carb is mounted). By removing the piston , then you can do a full visual of the cylinder to see if there is a crack or damage to it. From there you will decide if it only requires piston & ring replacement and for sure a new head gasket. Take a digital camera with you and take a lot of pics while disassembly so you have a good reference when putting it back. The rod caps require a 12-pt 1/4" socket to remove and install. After disassembly then order the parts and gaskets required.

If the cylinder is good to go and you decide to repair, I'd have the head checked by a machine shop to make sure it is not warped. If you do all this and put a warped head back on, you'll be doing it again. Just my .02. Been there done that.

 

[Jiggz]

Re: Force 125 (1987) Cylinder Help

If the cylinder is good to go and you decide to repair, I'd have the head checked by a machine shop to make sure it is not warped. If you do all this and put a warped head back on, you'll be doing it again. Just my .02. Been there done that.

The above recommendation is highly recommended if not mandatory. The reason being the #4 piston is different with the other pistons it is probably because this is not the first time this kind of thing happened and the real source of the overheating was never really identified and corrected.

 

[jerryjerry05]

Re: Force 125 (1987) Cylinder Help

The head weighs about 110# I just shipped one.
With the box I made it was 121#
If you've got a "leak" on the fuel pump side??
It's possible that's you problem?
Trying to lift it off, it has the exhaust tube connected.
It's about 14-16 in long.
So your gonna have to lift straight up and over the cowl and clear the tube.
I'm fairly strong but doing this aint easy with out help.

IF???? You decide to redo the whole motor?? You have to be real careful when removing the 4 screws/bolts holding the tube on.
Fill out the pofile,location? You might be close to someone who can help??
It's the easiest place to twist off a nut.
The exhaust passage cover, the bottom screws are the next place it's easy to break off the screws.
Fill out the profile? You might be close to someone who can help.

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

I completely agree with what everyone is saying... thus...

I'm torn between looking for a used head known to be good with good pistons, vs trying to work with what I have which might have hidden issues. What makes me wonder, is the whole reason I took the cylinder head off in the first place was because I had cleaned the carbs and they are fine to the best of my knowledge and research and yet I still had the poor idle / shutoff issue. My #4 is damaged for sure, but I can't tell if it's recent or how much the damaged piston crown would contribute to my original issue. The plug and the inside cup of the cylinder head for that cylinder had plenty of gas/oily residue to tell me that after cleaning the carbs it was firing and working at least.

I only have enough patients and money to commit to one thing right now and I can't make up my mind yet... spend a few hundred in bits and pieces and hope to have it all right, or spend 600/800 bucks in one shot for a one time swap out of a good working powerhead?

Yall might can tell I am a bit indecisive ;-)

It wouldn't hurt or cost much to remove the two lower return valve covers (fuel pump and one above) and remove the manifolds and inspect what I can... but to be honest I don't know much about what I am looking at except for the guidance of Youtube/Google and the shop manual I have... lol

 

[grininmonkey]

Re: Force 125 (1987) Cylinder Help

I know someone who works with glass and has some sheets, I'll check out the cylinder head using the method described in the shop manual I have... thank you for bringing that up!