looks like head gasket time,89 force 125

[sportrider]

I had an idling issue going on and after reading a few threads here I was hoping it was just a fouled plug. turns out the plugs were fouled which got it running the way it always has. I decided to run a compression test while the plugs were out and ended up with this. cyl # 1 125psi, cyl#2 120psi, cyl#3 118psi, cyl#4 30psi, I poured a little oil in #4 and retested and got 45psi. I'm thinking blown head gasket. I've yet to pull the head, are force heads prone to cracking?

 

[sportrider]

well.... I pulled the head. head looks good, I found someone has been in there before. one of the head bolts around #4 was stripped. nothing a heli-coil can't fix. the cylinder bores look real good, you can still see the crosshashing. #4 piston doesn't look so pretty. there is some warping on the face at the edge in a spot. I guess that is going to have to be replaced as well. looks like I'm going to learn these engines better then I wanted to.

 

[jerryjerry05]

Not a hard motor to work on.
I sent u a PM(I think) .

 

[sportrider]

I'll be happy to get it running up to par! I was going to try a different prop to try and improve the performance but after finding out I'm really only running on 3 cylinders I think getting those 125 horses back will be what I've been looking for!

 

[sportrider]

No Title

here's a picture of # 4

 

[sportrider]

nevermind

 

[sportrider]

No Title

duplicate post

 

[pnwboat]

Looks like a broken ring on #4.

 

[Jiggz]

Contrary to your belief, this is not warping on the edge but rings catching up on the exhaust port, breaking them and damaging the piston. Search the forum for "piston replacement" to get the details on the process and parts/tools needed to do the job.

 

[sportrider]

I'm going to mic the bore tonight to figure if its still standard. I found a few threads about the pistons but nothing in detail. I'm assuming to access the con rods the entire intake assembly has to be removed. I do have another question in regards to the pistons... what is considered normal play? to me all the pistons seem to have a lot of movement in the bore, I've rebuilt a car engine and the pistons were tight in the bore, all the pistons have noticeable movement side to side.

 

[Frank Acampora]

I can't tell you how many of these pistons with semi-keystone rings I have replaced. In the last year, I have replaced 2 on a 90, 1 on a 125, 3 on a 150 that I am using, and currently 2 on another 150.

They seem to be a weak spot and frequently break the top ring for no reason. If you have the money, replace all four with a quality after-market piston with square rings. Personally, I like Wiseco.

Pistons can be replaced through the reed openings. Take off the carb and the manifold with the reeds and the big end of the rod is accessible. The factory does not publish piston clearances but suffice to say that a normal piston CAN be rocked back and forth quite a bit. Remember: The pistons are cam ground and are not only tapered from skirt to crown (to allow for expansion under heat) but are oval shaped with a major and minor diameter to account for uneven heating and expansion in the bore.

If I remember correctly, Chrysler and Force engines set a tighter tolerance for wear: .002 oversized, tapered or out of round measured in several places just above the ports and higher up. If the ring has only nicked the exhaust port and done no real damage to the cylinder, the engine is usable with just a light honing. Deep scratches that can catch a fingernail must be bored oversized.

 

[sportrider]

I ran the piston through it's entire stroke last night and saw no visible defects in the bore the bore feels smooth. I looked at the ports and saw nothing obvious. I've checked the T-stat and its operating, the water pump seems to be flowing good looking at videos on youtube for comparison. when I bought it the needles where 2 1/2 turns out, they are now just a touch over a turn. i'm hoping it was caused by a tuning issue. I'd like to replace all 4 pistons but it's not in the budget right now and I really don't want to have the boat down long if i can help it. these things can never seem to happen at the end of season!

 

[Jiggz]

With the look of the damaged piston, it indicates the top ring caught the bottom of the exhaust port and sometimes that is hard to see until you remove the piston. Next move is as discussed by the Supreme Mariner, is to remove the piston through the intake opening. Get a detailed analysis of the cylinder, hone and then measure before ordering the new piston. Take note of the original piston as it will tell you if it is still standard or already oversized. This is usually stamped on the head of the piston. And yes, Wiseco piston kit is the only way to go for replacement unless you like doing this frequently.

 

[sportrider]

I probably already know the answer to this because it seems like a dumb question to me but, anyone running mismatched pistons? could I get away with a wiseco on # 4 for now and replace the rest at a latter date?

 

[Jiggz]

I did mine about two years ago on #3 cylinder and so far it is still working great. Although, I might add that the replacement piston was the same size as the broken one, i.e. std. but even with a little oversized piston, I do not think it matters that much. Of course, budget permitting, I'd rather do all the pistons with Wiseco's but that is just not possible right now. This is the very reason I still have my Force. Lol

 

[sportrider]

I guess I'm just outta touch with reality! I was thinking about re-powering the boat I paid $1700 for... then I priced out what a new outboard would cost and thought 125 hp was plenty! lol

 

[Frank Acampora]

The cubic inch displacement of the engine is so small, that it simply will not see the difference if you need to over bore. Running a single Wiseco is acceptable, again, the engine simply does not care and will not notice. I recommended replacing all four piston as a pro[phylactic measure because stock pistons and rings are so prone to breaking the top ring. Better to take an extra 2 hours now than to break another ring down the road. However, If you don't have the money there is no guarantee that the remaining three pistons wont last forever.

 

[sportrider]

here is the piston, no question its done! the port is going to need a touch up. there is a little scrape in the cylinder wall. it measured out at 3.312 so a standard piston is going back in it. I'm going to dremel the port tomorrow and hone the cylinder. any tips on how to reassemble the con rod without the bearings falling everywhere. I had to fish all 16 rollers with a magnet, installation seems like it might be a challenge.

 

[jerryjerry05]

You can run mis-matched pistons.
I can't open any pics.
Did you find any oversized pistons in the other holes?

 

[sportrider]

no all the pistons are standard size, I mic'd all the bores and they are the same. there is no stamping on any of the pistons to indicate oversized bore either. I ended up ordering a Wiseco 3129 piston and the bearing kit it said was required for the piston