compression problem

[fmfmedic]

I recently bought a 14' Bayliner Capri with a 1985 Force 50 on it. It runs, but when I put it in the water and advanced the throttle it died every time. Checked the compression and it has well over 100 lbs on one and 0 on the other. It also has a leak in the lower unit, letting water in. got a kit for the lower unit. Now I need to know two things. 1: Is it worth fixing, and two; Where should I start looking in the powerhead? I've never seen a cylinder with NO compression. There is no visible damage to the piston through the spark plug hole, the piston does move, a broken ring would leave (I should think) scoring on the cylinder and there isn't any. There is no evidence of a leaking head gasket. I thought a broken reed valve? Any suggestion? I don't want to tear this thing completely apart if I can avoid it.

 

[Justinde]

Re: compression problem

Some of the other guys may want to elaborate here, but a head gasket is an easy fix, especially on a 2 stroke. No valves to worry about, just torque it up in the right sequence and to the correct torque. At least taking the head off you will see the actual condition of your pistons and cylinders. If it was me, I would definately do the head gasket, especially if you are going to kit the lower unit. I am so unbelievably happy with my Force Engine, it is easy to work on, runs very well, it has a couple of things I'd like to fix, which are more quirks than repairs required, but all in you can't go wrong. There was another post on this site with 3 healthy cylinders, and one showing 0 psi. He did the head gasket and bingo, runs strong.

Cheers

 

[jerryjerry05]

Re: compression problem

Gotta remove the head and see what's hiding in there.Post some pics.J

 

[fmfmedic]

Re: compression problem

Will do. Might be a couple days. It's outside on the boat and the temp hasn't been above 30 for the last week. Supposed to go up tomorrow. Thanks.

 

[jason32038]

Re: compression problem

Like jerry said start with removing the head. Check pistons and cylinder walls. Even with a leaky head gasket you shouldnt have 0 psi. Could be scored rings/cylinder/piston or stuck rings. One powerhead I have has 2 scored cylinders. If the scoring is bad enough it will score the rings closed (basically welds or distorts the metal on the pistons to hold the rings closed and you will have 0 compression. The reed valves will not affect compression they only allow fuel and air to enter the block. Sort of works like an air compressor without the fuel.

 

[antique fisherman]

Re: compression problem

Had the same problem with a Chrysler after it overheated . I removed the head and couldn't see any damage . The gasket also looked great . I replaced the head gasket with a new one . I have run it about 20 hours since with NO problems. Good Luck and HAPPY BOATING.

 

[fmfmedic]

Re: compression problem

OK, it warmed up and I got the cylinder head off. Head gasket looks relatively new, no gaps or breaks, as you can see. However, the top piston looks like a ring broke and got caught in the exhaust ports, or something else broke and poked through the port. The damage to the piston matches the ports exactly. Now what should I do. It looks like I need to disasemble the power head and pull the piston, and I still don't know if the motor is worth it. The local shops won't work on it.

 

[Justinde]

Re: compression problem

I'm lost! Hard to tell from the pics ( from here), however, If the damage is as you say, look for a new block/powerhead on ebay, or iboats, and decide for yourself if it is worth the hassle. All I know is that my Force engine is as reliable as **** and easy as so far, to work on. I would look at the investment in a new block, and compare to a new engine. I reckon you will still be ahead by miles.

 

[jason32038]

Re: compression problem

Cant tell how bad the cylinder wall is but the piston is def. damaged. You most likely need that cylinder resleeved and bored to the next borable size of the other cylinder. New pistons and rings. Usually the bearings are reusable. If you cant find anyone to work on it try a machine shop. Some auto machine shops do marine work.

 

[fmfmedic]

Re: compression problem

Thank you Justine and Jason32038. I checked on iboat and they don't sell power heads, just the parts. Rebuild, assuming all I need are piston with rings, gasket set and head gasket, will run about $150.00 in parts. Haven't checked for sleeve prices yet, and I'm not certain I need to. There doesn't appear, by visual or touch, to be any damage to the cylinder wall. There aren't even any ding marks on the exhaust ports where the damage to the piston is. Personally, I think something came loose and was bouncing around in the exhaust area and got caught by the piston when in happened to hit the ports. I'll look for it, but it's probably gone now. The motor turns very easy, with no sound at all.

My motor is a 507X5A. I found a 507Y8D (1988) 50hp powerhead for $300 on ebay. Could anyone tell me which power heads will fit on the lower unit? If I'm going to replace the entire power head, I'd like to put a bigger one on it, maybe 60 hp, or possibly a newer model year. I don't know where to look for that information.

 

[fmfmedic]

Re: compression problem

Answered my own question, partly. 81-87 'A' powerheads were the same. 1988 used totally different spacer plate.

 

[fmfmedic]

Re: compression problem

Went out and took another look, trying to find what damaged the piston. Noticed that the lower cylinder, with a good piston, has scoring on the cylinder wall. Looks kinda like something got caught between the piston and the cylinder wall and just scratched it's way up and down. I think this is what damaged the upper piston, until is fell down and got caught. You can see and feel it when piston is at TDC. Scoring isn't deep, and I can't find replacement sleeves on the net yet.

I'm going to tear it down and see just what is going on. It gives me a good excuse to buy a dial guage to measure the cylinder anyway

 

[Justinde]

Re: compression problem

Before I bought my 125 Force, the guy I bought it from had done the powerhead/gearbox/ignition etc. New piston's, bored and honed, and they spent some good coin on her. $4500 Australian dollars ( about the same in US now ). My boat pulls 44MPH and I am sure it has a little more. I am stoked with it. Again, I could probably replace the engine for a late model 4 stroke injected, but then I could not work on it.

Best of luck with yours- do you have the Clymers manual for it?

Cheers

 

[jeffersondodson561]

Re: compression problem

I personally would stay away from Force's all together, they were very reliable, easy to work on but after Mercury dropped them the died. Murphy's law says after all the headaches of rebuilding it you will have problems with the gearcase etc.
F*cked
Over
Rebuilt
Chrysler
Engine

 

[Justinde]

Re: compression problem

Thanks Jeff!!

Every engine. Every Car. Every PLane. Everything you pretty much own will take care of you if you take care of it. A neglected Mercedes will be a ****box. A loved Hyundai will be a dream. If you do rebuild, every year, change gearbox oil, change plugs, and do you routine maintenance. If you take care of it, it will take care of you! There are no bits that will just pop or go bang unless they are neglected.

Easy to work on, parts availability mostly! I'd rebuild if the $150 or so plus your time is about right.

Shame on you Jefferson!

Your loving Force Owner in Sydney

Justin

 

[jeffersondodson561]

Re: compression problem

If it F*cks, Flys, or Floats, its goint to give you problems!

 

[jerryjerry05]

Re: compression problem

These motors are EASY to rebuild.Any competent machine shop can rebore a sleeve. Don't think about resleeving.Not worth it.
If you really want to work on it.Get it bored out .010 and new pistons/rings.
Look on e-bay they will have something sooner or later.
Some people who shouldn't post if they don't have any help to add.

 

[Justinde]

Re: compression problem

Thanks Jerry

I think I was more subtle! Look around for bits- they are NOT hard to come by, and rebuild if ou have the inclination to do so. Again, my boat is a monster, and now pulls 46mph. Take good care of it, and it will take care of you!

 

[JIMMIKRON]

Re: compression problem

I have the same boat & motor. The Force 50 has poor cooling jackets. Check for piston slap. My opinion is this motor is crap. Hate to be the bearer of bad news.

 

[dustinbrown42]

Re: compression problem

I am new to this site and this was a similar post to my question. Site wont let me post my own thread for some reason. I have a 1994 Force 70 HP. Compression in 2 of the cylinders is in the 90s and the 3rd cylinder is in low 80s. Marine shop told me need to rebuild as there is scoring in the cylinder walls. With this motor, would I be able to recore, new pistons, and rings for a rebuild, or is there more required? Costs, etc? I'm not motor savvy, but a buddy of mine is and want to know if this is something he could fix, and be able to get the parts to.