1990 3.0 OMC Cobra

[wrench 3]

If you get what's left of the bolts red hot or close to it and then let them cool completely, they should pretty well turn out with your fingers.
The cranks should be the same but I'd be more inclined to do a compression test on the other engine, pull the pan and make sure that none of the crank bearings have been hot, and if all's OK use the hole engine.
I don't believe that they use the dowel in flywheel any more. It was only for assembly purposes anyway.

 

[josh08]

I managed to get all 6 out. I did have to tap one. I have ordered 6 new studs and locknut's. I have never seen flywheel studs and nuts be this exspensive, it was $145 shipped with a new outdrive gasket kit. I am going to apply blue loctite 243 when I reassemble. I am still however trying to find out the reason they all sheared.

 

[josh08]

I received the new studs and nuts today. They fit good in the crankshaft but are loose going through the flywheel and coupler. I was thinking they should be a snug fit. Does anyone have any opinions on this?

 

[alldodge]

The flywheel should fit on the crankshaft and will be keyed. Once placed on the crankshaft, there should be next to no play between the two.

The studs do not need to be a tight fit and usually go on with fingers

I'm finding 65 Ft Lb for the bolts

 

[josh08]

The studs do go in the crankshaft finger tight, but they do have some play on the flywheel and the alot of play on the coupler. The coupler is wobbly on the studs.

 

[wrench 3]

The studs do go in the crankshaft finger tight, but they do have some play on the flywheel and the alot of play on the coupler. The coupler is wobbly on the studs.

As long as the holes are still round and not worn oval I wouldn't worry about it.

 

[josh08]

The variance between the stud od and the hole in the coupler is .057 or just under 1/16. But the coupler does wobble some on the studs. I have noticed the studs i removed were not the correct ones. They were fine thread on the crank side and not on the nut side. I'm assuming the short threaded side goes in the crankshaft with the side having the most thread going through the flywheel and coupler for the nut to go on. An I correct about this?

 

[wrench 3]

You're correct, short end into the crank, long end through the flywheel.
As I said before if the holes in the coupler were worn they would be oval. Make sure the mating surfaces are clean and the washers are on the studs. Then torque it to specs.

 

[josh08]

I'm attaching pictures of the coupler and flywheel

 

[josh08]

This is the broken stud and piece I removed from the crankshaft. Whoever installed it prior installed it backwards apparently and with the wrong stud. The piece I extracted from the crankshaft was around 1 inch.

 

[alldodge]

If the threads are not correct don't use them

the coupler does wobble some on the studs

The coupler should not wobble, the center of it should fit inside and flat against the flywheel. If it wobbles just holding it in place see what is causing it

 

[wrench 3]

The studs were probably a grade 3 or 5 instead of an 8. Plus the course thread would reduce the clamping load.
A couple of the holes on the coupler definitely look damaged. It should be replaced.
I could't get as good a look at the flywheel. There may be damage around the holes but I can't say for sure.

 

[josh08]

I got everything back together and the first time I turn the key it sounds like the starter grinds or makes a strange noise maybe not engaging, then I turn the key the second time and it starts right up with no noise and runs great. It done this repeatedly the several times I tried it. Keep in mind it was making that same noise when the flywheel studs were sheared. The starter was replaced last year prior to me buying the boat. Also one of the screws that attached the motor mount down into the fiberglass on the front of the motor doesn't want to tighten down.

 

[alldodge]

The starter was replaced but sounds like it has an issue. Its not engaging and therefore grinding but does probably move the flywheel, trying again the teeth fully engage

Also one of the screws that attached the motor mount down into the fiberglass on the front of the motor doesn't want to tighten down.

Should have looked at prior to installing the motor. Need to determine how much rot is in the mount. Then dig and/or drill out the bad. Fill with new wood and secure with epoxy, then redrill for bolt

 

[wrench 3]

I'd replace the starter drive and clean the plunger in the solenoid that pulls the drive in. It may be rusted.
I'm hopping that that stringer is in fair shape.