Advice on changing bottom piston in 1993 Force 150

HotTommy

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Mar 15, 2013
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Last summer my 1993 Force 150 outboard suffered damage to #3 and #4 pistons when, apparently, one ring failed triggering an overheat and subsequent damage to the adjoining piston. This is an engine that had already had the #1 piston replaced for a similar reason. With that experience, I have decided to replace all the remaining original pistons. ... Having done #1 already, I know how to do the job, but I have questions about the best way to approach replacing the #5 piston.

The cowl obstructs an easy view into the #5 cylinder. That leaves me to choose from three apparent options. One, leave everything in place and do the job while working around the impediments created by the cowl. Two, remove the cowl. And three, remove the powerhead to do the job. Options 2 & 3 involve a lot more work, so I'd like to hear from any who have experience doing this job. If you'd like to share your opinion on the best way to do this job, please note whether you have actually done it.
 

Nordin

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Jun 12, 2010
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First I want to clarify I have not done it on a 150Hp Force.
But have have done this on a Chrysler 75Hp and I think the problems are similar.

The big problems are.

#1 When you have to remove the piston rod needles and the carriers for the crankshaft.
#2 When you have to assemble the needles and the the carriers.

The chance to drop one or more needles is 95% of 100% !!!!!!!!!
And then you have to fish/pick them up from the crankcase. GOODLUCK!

#3 When you shall line up and torque the bolt for the piston rod assault.

There is no space to check with the pencile and feel that it is lined up.


This can be a really PIA and you must stay really calm and have alot of patience.

If I was in you I would move the powerhead from the leg and work from there.

Sometimes a shortcut can be................PIA.
 

HotTommy

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I'm no expert, so take what follows for what its worth. ... I swapped out pistons 2-5 without removing the cowl that obstructs access to #5. Doing #5 was as challenging as the other 3 combined, but I did get it done. Here are some lessons learned for anyone who stumbles upon this thread in the future. First, I drilled a 1/2" hole in the cowl in line with the center of the cylinder at the back. This allowed me to use a hone to clean up the cylinder. It also allowed me to use a rod to tap the new piston into the cylinder. I used a steel rod with a wooden block on the piston to protect it. ... It was difficult to fit the piston with the ring compressor attached in the small space between the engine block and the cowl. If I put the piston part way in first, I could fit the ring compressor over it, but it was difficult to tighten up the compressor with everything well oiled. I solved that problem by using a 4" hose clamp over the ring compresser. .... I ran into one more problem on #5 that may have had nothing to do with its location. I was having a hard time getting the piston all the way in to fit the connecting rod to its cap. I eventually discovered that the connecting rod was sliding down the wrist pin far enough to allow the cap end to contact the crankshaft. I solved the problem by putting a thick glob of bearing grease around the wrist pin to inhibit the rods downward motion.
 
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tommarvin

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Nov 22, 2015
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I have never done this, and I would never do it without removing the power head, why make an easy job hard.
You have all the time in the world, how much longer is it going to take to remove the power head ,and do it the easy way,and make sure it's done right?
 

HotTommy

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I have never done this, and I would never do it without removing the power head, why make an easy job hard.
You have all the time in the world, how much longer is it going to take to remove the power head ,and do it the easy way,and make sure it's done right?
I would agree if the bolts cooperated. I have broken the heads off several bolts trying to remove things and I'm a little gun shy about removing things that don't absolutely have to be removed. And like I said, I'm no expert either.
 

jerryjerry05

Supreme Mariner
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May 7, 2008
Messages
18,126
I remove the block when I fix a cylinder.
​But I rebuild the whole motor not just 1 cyl.
This included the exhaust chest and the transfer ports and recirc system.
The piston went bad for a reason which is not always evident when you do just 1 cylinder.

Frank does the piston replace without removing the powerhead.

Depending on the damage????
If the piston or cyl. isn't too bad I'd say sure work through the front.
​When rebuilding 1 cyl. the bearings can be a bummer.
Use "bearing assy. grease" regular grease doesn't dissolve very good.
It can stick in place and cause bearing failure.
 
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tommarvin

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Nov 22, 2015
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You are not alone" Hot Tommy" I'm afraid to remove any bolts unless it's snapped off broken too.

I watched You-tube videos on removing snapped bolts, you punch a indent as close to center of bolt as possible, get an 1/8 inch carbide drill bits only on E-bay,a pack of 10 bits, drill on both ends of bits, then get larger and larger, until you get to heli coil size then tap correct size for Helicoil.
Machine shops will remove snapped bolts too,
I think this is one reason why Force motors are so inexpensive, We stole a bay liner trophy 19 ft CC with a 1988 force 125HP for $2,500.00 on CL,and had to drive 16 hours round trip to pick it up and drive home. Side note, get there reach for the hundreds in my front pocket, the guy says aren't you going to offor me less, I said no I want the good karma points . Boat was in very good condition, came with a kicker, downrigger hummingbird depth finder.
The point, fear not, let's not let snapped bolt ruin our day,just think how easy it will be to remove next time.,
 
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