Need Help With Force Motor

[brianvolt7]

Re: Need Help With Force Motor

More pics of number 4 and head gasket.
Should I fix the rings put a new head gasket on it and sell it? Or is it worth replacing the piston on number 4 and keep it.

 

[brianvolt7]

Re: Need Help With Force Motor

Can I use JB weld on the chip?

 

[pnwboat]

Re: Need Help With Force Motor

Looks like the bottom two cylinders ran lean. The pitting in #4 piston is due to melting. I would not consider re-using that piston. You can also see some evidence of excessive heat on the head itself in the combustion chamber for #4 cylinder. The missing chip is a piece of the block that supports the steel cylinder liner. There must have been some serious heat or detonation that occurred to break it off like that. I would have a machine shop take a look at it to determine if there is any damage to the steel liner itself. I would also consider the possibility that the block may not be serviceable.

 

[brianvolt7]

Re: Need Help With Force Motor

I am searching for a piston on line and the parts are different for A motors vs. B, C and D. Do you know where I can find this on the motor? I know I had an A forward gear lower until I changed it.

 

[pnwboat]

Re: Need Help With Force Motor

There are two different piston sizes used in the 120 HP motors. Most 1990 120 HP motors use a 3.312 in piston. The other size is a 3.375. It is not advisable to purchase pistons before measuring actual cylinder bore. Measure first, determine if the cylinder needs to be bored out, then purchase piston(s). Without measuring, you're taking a shot in the dark and possibly wasting some time and money. Service limit for replacing piston is .002 - .003 in. of wear. Too close to eyeball.

 

[brianvolt7]

Re: Need Help With Force Motor

I am guessing I need a special tool for this? Some sort of caliper? Can I pick one up at Autozone?

 

[pnwboat]

Re: Need Help With Force Motor

You need a bore gauge. Not sure if Autozone has these to lend. I usually let the machine shop handle those duties. They're the experts and do this on a regular basis.

Sent you a PM.

 

[brianvolt7]

Re: Need Help With Force Motor

pnwboat,

I will check with Autozone for the bore gauge.

If they need bored, would I need to buy all new pistons as well as rings? Will all the cylendars need bored or just the bad ones? Also, do you know roughly what a machine shop charges for this kind of work?

 

[pnwboat]

Re: Need Help With Force Motor

Just the bad ones need to be bored and fitted with new over-size pistons and rings. Some machine shops will try to talk you into boring all of the cylinders, but it's not necessary. Prices for boring run anywhere from $30 - $50 per cylinder. Forged piston kit with wrist pin, bearings and rings run $80 - $100 each. I would have a machine shop take a look at the chipped area. This is where the head gasket seals. It also appears that the head gasket failed at the same spot. No sense in putting any money into a block that keeps blowing head gaskets.

 

[brianvolt7]

Re: Need Help With Force Motor

Yah, I don?t want to keep putting money into it. It may be better for me to put a stock piston in it and re-ring the others, new head gasket and sell. What do you think?

I got the intake manifold bolts out but I can't seem to get it to separate from the top end. Was I supposed to pull the flywheel and all of the electrical stuff as well? Or is there a trick to removing this. I want to pull the pistons out but I think I need this off to reach the piston rod bolts and bearings.

I am also having trouble removing the block from the lower unit so I can take it to be looked at, do I need to remove the flywheel for this as well?

 

[brianvolt7]

Re: Need Help With Force Motor

forget the last post, I got the two bad pistons out, I think the hard part is going to be getting the new ones back in with those bearings. Maybe some grease will hold them in place.

They are pretty bad, I am going to post pics later.

 

[PaulO]

Re: Need Help With Force Motor

I had light scoring in one of my cylinders as a result of detonation melting the top of the pistion and a .010 Oversize bore cleaned it up beautifully. Don't worry about buying a micrometer. Let the engine shop do it. You will know exactly whether to proceed or not with the bore.

This has definately been a thread of commitment for all involved

My bore 1

My bore 2

When I checked the timing after rebuild I found it was set to approx 40? BTDC at cranking so that was probably 42? when running at WOT. No wonder the thing sh1t itself.

It certainly makes me wonder about the quality of work or if it was set up for an insurance claim???

 

[brianvolt7]

Re: Need Help With Force Motor

My biggest problem is that I can't break the block off of the motor. I have removed all of the bolts up top and the lock nuts below and It just wont budge

My cylinders are not scored, but I still want to have a shop look at them for boreing if necessary.

The other problem is the chip on the number 2. Another subscriber sent me a link to a block for sale on line that I am considering.

 

[brianvolt7]

Re: Need Help With Force Motor

And believe me I know this is a long haul thread, and I appriciate everyone who has hung in there with me. Thanks to everyone!!!!

 

[PaulO]

Re: Need Help With Force Motor

I had the same problem. The I realised there is a nut at the back underneath dead centre that was in the shade. I couldn't see it. Then I got a crow bar, sat it on the 2 inch square lug on the back centre leg and leavered the little prong on the block. Be careful, I tried to prize the block with the hidden nut still on and broke one lug off. there are two lugs, one each side of the block down near the attachment to the leg.

 

[brianvolt7]

Re: Need Help With Force Motor

I did get the nut off just above the exhaust boot, is this the one you are refering to? I will need to take off the skirt just under the hood to get a crowbar in there. Do I need to remove the flywheel to remove the block? Once it is broken loose, how much does it weigh? I don't have a cherry picker but I do have a Bobcat that I can hook a chain to if needed. I would rather my sons and me just pull it off, I am not sure where to hook the chain without damaging the motor.

 

[pnwboat]

Re: Need Help With Force Motor

There is usually a bead of silicone sealant between the block and the lower leg that is probably preventing it from coming off. Sometimes you can get a thin bladed putty knife in between the adapter plate (which is bolted to the block) and the lower leg to cut through the sealant. Once you get a small spot started, then you can usually work it off. You don't have to remove the flywheel to remove the block. There is a nut on the shift linkage that is below the bottom carburetor that needs to be removed too. It's really buried in there and is kind of hard to see and get a wrench on.

 

[brianvolt7]

Re: Need Help With Force Motor

Is the silicone the same as the same reason that the intake wont come off? I did get the shifter nut. I will give the blade a shot.

Just as a backup plan, I found an 88 125 force long shaft with good compression and is running perfect, according to the add The seller has provided me with the number for the shop that just serviced it. Comes with cables and tilt unit too. It has new paint and looks nice in the pics.

The good news, $1000 or best offer.

Do you think this is a good deal? Will this bolt up to my boat or will I need to drill new holes? Do you think the shaft is right for my Bayliner cuddy?

 

[pnwboat]

Re: Need Help With Force Motor

$1000 bucks is a bit pricey for my blood. Especially for a used motor. They always run good and have good compression....according to the advertisements.

Don't take their word for it. At least check the compression.

 

[brianvolt7]

Re: Need Help With Force Motor

pnwboat,

I am going to call the marine service today that did the work on the used motor. What do you consider an acceptable compression for this motor?

I am considering this because I broke down the cost to rebuild, about $690.00. This is with purchasing four +.030 piston kits at $100.00 each (bearings, rings, pistons). this is assuming paying 140 for the block (I dont know what the bid is today) and 50 gasket kits and 100 for misc parts/machine work. After hearing your advice, I dont think I will offer 1000, I am thinking 700-800 if the marine service confirms the condition to be good.

Back to the rebuild. What will I have to do to my block to prep it for hone work? Can I leave the flywheel on? Also I was unable to figure out how to get the piston pin out. There were not any clips or anything, does the shop need to do this? One last question can any machine shop do this work or does it have to be a marine machine shop?