1998 Force 120 Exhaust housing

[BoatingCop]

Ever since I bought my boat I've been trying to track down a stumbling/poor acceleration issue. It's also had an idle issue. Compression is good 130 psi all around, Both carbs were removed and cleaned, and spark checked out well. One thing that I haven't thought about is the exhaust housing/cover. I bought this boat damaged from a hurricane. The swells sent the boat into the top of the boat house that it was in. When this happened, it cracked the top of the exhaust housing. The P.O. had JB welded it back together. I notice that while running a little water leaks out of the top of the JB Weld, and has progressively got worse. I recently was running the engine on the hose and the flusher slipped off for a second. As the water pressure in the engine got lower, the better the engine ran. Could this crack in the top of the housing be causing my poor running condition? Does this mean that the block is toast do to the housing being part of the block? As far as I can tell, it's not oil water coming out of the crack. I'm beginning to think that I may just need a new power head. Any thoughts on this? Thanks!

 

[jerryjerry05]

Pics of the crack?
Any water in the cylinders?
Remove the exhaust cover.
Being as it's been in salt water be VERY careful when taking the screws out.
They are 1/4-20 and will twist off in a blink of an eye.
Leaving you with a whole lot of work.
I use PB Blaster and a torch and a hammer.
Spray and heat and tap and GENTLY try to turn the screws.
It took me about 2 hrs. to remove the 2 bottom screws on a motor I rebuilt.

 

[BoatingCop]

I've checked for water in the cylinders in he past but found nothing. I was also checking way later in the day, long after it was ran. I can't pull the cover because the PO epoxied over the top. Here's some pics.

 

[jerryjerry05]

If you decide to remove the cover.
The torch will make short work of the epoxy.
Just heat it and it should cook away.
Look into the throat behind the carbs.
Kinda sounds like it might have a bad reed??

 

[BoatingCop]

Thank you, I'll check that. Should I be able to see well enough without removing the carbs? Here's another one of the pictures I posted. I don't what happened. You don't think that would be letting water in the cylinder though? Thank you!

 

[jerryjerry05]

No you can't see through the carbs to the reeds.

 

[Frank Acampora]

The JB covering the cracked water jacket is VERY suspicious. Yes, depending upon the severity of the crack it can be leaking water into the exhaust and thus into at least one of the cylinders. Do the spark plug(s) look steam cleaned?

While JB is very good for some purposes (I used it to mount towel bars to glass tiles in my bathroom---they are so hard even a diamond drill has trouble drilling them) it is not magic.

You should try to pull off the exhaust cover and examine the top of the water chamber. Judging by the rust on the flywheel it is likely you will break some of the bolts and need to drill them out. Before drilling and re-tapping check the internal exhaust chamber. If it is cracked internally, you have an anchor. Don't bother fixing stripped screws. Unless you can find a very good welder to actually weld the crack start looking for another used but good condition block.

 

[BoatingCop]

Thank you for the reply Frank. I haven't got to tear into it yet, however I was afraid of this. When it ran better, when the flusher slipped off for a split second that one time I figured it may have something to do with water leaking in. I'll try to get the cover off and I'll also take a look at the reeds. I think I'll start looking for a new powerhead as well. Thank yall so much!

 

[BoatingCop]

So I did a little looking and found what looks to be a very clean Force 125. He wants $500 for the whole thing, which I think is a pretty good deal. Of course this is pending a compression test and an overall walk around. The engine looks identical to mine, but the owner is unsure of the year or anything else because the data sticker is missing. The only reason he believes that it's a 125 is because of the cowling. In the late 90's were there any major differences? The reason I'm wondering is because I want to pull this powerhead from this motor and put it on my motor that I have. I know there's some kind of difference between the 120 and 125 but I don't know if its internal or external. I just don't want to go through the trouble if I get all the way to that point and it doesn't line up. Thanks and sorry about the winded post. Here's some pictures of the motor that's for sale.

 

[BoatingCop]

Well, I talked to the guy with the motor and he said he JUST sold it. Dang it!! Oh well, I went out and decided to break off the JB Weld on the top of the exhaust cover to assess the damage. HOLY COW!! It chipped off quite easily and when it came off, there was a hole where the cover is supposed to meet the block. There was nothing separating the water jackets from the inside of the exhaust area. After I took this picture, I was able to chip more away and found that there was a piece of metal that was bend and covered with JB Weld to cover another hole. So all in all, water was streaming straight into the exhaust housing. My block is toast and I'm on the hunt again for another power head. Ugh!! If I could find a 25" complete motor for cheap I'll do that too. These are mostly 20" shafts though. Here's the pictures.




In the picture above you can see in the middle of where the exhaust cover meets the block, that curved piece of metal. That was channeling water straight through the crack in the top and into the exhaust chamber. I'll pull the head in a few days just for kicks.

 

[Frank Acampora]

All may not be lost! If there are only surface defects on the sealing surface of the block, the exhaust chest can be milled down a bit. Then buy a new stainless plate, cover, and gaskets.

If however you decide to buy a replacement block. be careful. While the 120 and 125 blocks use the identical mounting pattern, carbs, and electronics, they are not the same. The 120 has a bigger bore and shorter stroke and is probably the better engine. However, no matter which one you get, be CERTAIN it comes off a late Force with the Mercury lower unit. The crankshaft splines are different. Earlier Force blocks/crankshafts will not mate with the late model driveshafts.

 

[BoatingCop]

Ok, thank you for the info! I was looking for the ones with the Merc lower unit, but was not aware of the difference between the 120 and 125. I'll look for a 120 specifically from '96-'98. I looked on ebay for long blocks but they're kind of pricey and you don't really know what you're getting a lot of the times.

I may look into filing down the block. However when I tried to remove the cover, I only got 3 bolts out without snapping them and the two bottom ones are rounded off. If I do try to mill the block I'll be having a machinist do all the drilling and tapping! Thanks again!!

 

[jerryjerry05]

They stopped making the 125/85 in 1990.
Anything after that is a 120 Like Frank said the Mercury stuff won't work on the older motors.
In 1990 they started changing to a different drive and different equipment.
boats . net has a good selection of parts diagrams.
If you look up any possible new motors on here they can tell you what works and what won't.
Lots of time a model change can be something as small as using a different bolt or screw.

And $500 "was" a GREAT deal. The parts alone were worth that.

 

[BoatingCop]

And $500 "was" a GREAT deal. The parts alone were worth that.

I know!! It's just my luck too, because the motor had been on craigslist for 10 days, and someone called an hour before I did and bought it!! Oh well. Thanks for the info! I'm still on the hunt. I'd like to find another motor and steal the powerhead still, that way I'd still have an extra LU. I'll still do it as long I don't find a good deal on another 25" shaft motor.