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150hp Force shearing flywheel key

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budguyal

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"I was looking at a boat for s

"I was looking at a boat for sale today , it's a 91 Cobra and the guy says it keeps shearing the key for the flywheel, has done it several times since last year.
Any one ever had a similiar experience? Wondering what the problem might be, other potential problems to look for that could be causing this. Need some info to help decide if this is something I want to get into, price aint bad if repair costs are reasonable. Thanks for any info that could help."
 
"Alan, there are two common ca

"Alan, there are two common causes of a flywheel key shearing.

1) timing is a little out of whack so when the motor first fires it gives a hard jolt which shears the key (easy - fix the timing before it causes piston damage as well)

2) the flywheel either isn't torqued down to spec OR the upper crank taper has been deformed (most likely because the flywheel wasn't torqued down).

If the crank taper is past the point of where it can be used, the fix will cost more than the motor is worth.

Onto the motor itself, even if it was running without issue. It's a 150 Force, an orphan even for a Force (which is no longer produced). This is a weird 5 cylinder design.

To replace the ignition system on it will cost you a small fortune - and they break - alot - OEM parts would go over 2 grand if the stator goes and takes out the CDM's (a common thing with these at this age).

Best advice I can give you is determine a fair price for the boat/trailer without the motor, because a 150 Force, in and of itself, that is shearing flywheel keys is worth maybe 300-400 bucks as a "parts motor" as long as it remains whole - it's worth more than that if it's disassembled, with individual parts tested and the good stuff sold off.

Force wasn't a terrible motor, but they were made from parts left over from the bankrupt Chrysler Outboard. This particular model was assembled by Merc who also threw on some stuff they had kicking around the discontinued warehouse. So the day the motor was built it was almost 20 years old "technology" wise, and now nobody builds them at all....

It may be a decent project that could leave you with a functioning motor, but just don't place much value on it when you are trying to determine a fair price - plan on replacing the motor if you buy this boat."
 
"Graham,

Thank you so much,

"Graham,

Thank you so much, this was exactly the type of advice I was looking for. I appreciate it a bunch.
This is really a great site, thanks to guys like yourself."
 
"If the flywheel and shaft are

"If the flywheel and shaft are not too bad and the flwheel isn't cracked, I would try a cold hi perf epoxy like "Marine Tech" to fill the imperfections and stabilize the tapered union. Torque to specs with a new keyway making sure you are degreed right on. You might save the motor for awhile if this is done by a very competant tech. Its my hunch that some work requiring flywheel removal was done at one point in this motors life and flywheel nut wasn't torqued properly, resulting in the damage. Now the flywheel is out of time. Good luck Alan"
 
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