1988 35 hp crank/Flywheel question

[spence88]

I have a 1988 mercury 35 hp outboard. Four of the eight bolts holding the flywheel together sheard off. Long story short. I broke the main flywheel nut trying to remove it. I didn't realise the crank was tapered. Can the nut be replaced, or am I screwed?

 

[Chinewalker]

Bigger question is how are the threads on the crankshaft? Nothing special about the nut, but the crankshaft can't be boogered up. Did you take the flywheel apart? It needs to go back together the same way it came apart for timing purposes.

 

[spence88]

No Title

Is it common for these nuts to break like this? The threads on the crank are fine. I didnt know the eight bolts were holding the flywheel on. I didn't need to remove the main nut. Guess I should have done some research, instead of assuming. Is it common for these bolts to shear off on this motor?

 

[racerone]

The flywheel is removed by removing that nut and using the proper puller !----No need to remove those 8 bolts at all.

 

[Faztbullet]

Threads look mushroomed to me......

 

[60sboater]

You only needed to remove 2 of the 8 bolts....180 apart and use a harmonic balancer puller and two long bolts where the short ones were removed.

 

[Chinewalker]

Yep, your crankshaft tip looks mushroomed. I'll bet that's why your flywheel nut split - it was trying to expand. I've never split a nut like that, so that's the only thing that makes sense to me. You might be able to use a die to re-do the threads, but it'll take some effort.

And, yes, it's likely you'll break those bolts on the outer rim - they use a thread locker on them as you really don't want a bolt loosening up on you when the flywheel is spinning 5500 RPM...

 

[spence88]

No Title

Yep, your crankshaft tip looks mushroomed. I'll bet that's why your flywheel nut split - it was trying to expand. I've never split a nut like that, so that's the only thing that makes sense to me. You might be able to use a die to re-do the threads, but it'll take some effort.

And, yes, it's likely you'll break those bolts on the outer rim - they use a thread locker on them as you really don't want a bolt loosening up on you when the flywheel is spinning 5500 RPM...

The crank is definitely mushroomed/tappered but the threads are fine. I don't understand how it could have happened unless it was factory. I guess I'll order a new nut and see if I can get it back together.
I never got the whole flywheel apart, seeing how I only needed to remove the part with the starter teeth. (Wish I knew that from the beginning) Four of the eight bolts sheared off one day at the lake.

 

[Chinewalker]

You'll need the correct die for the crank threads, even thought he threads "look good". You will not get a nut on there the way it is now.

If the broken bolts have any of their shank exposed, with the flex plate removed, you might be able to grab it with vice grips and back them out.

 

[spence88]

No Title

You'll need the correct die for the crank threads, even thought he threads "look good". You will not get a nut on there the way it is now.

If the broken bolts have any of their shank exposed, with the flex plate removed, you might be able to grab it with vice grips and back them out.

Are these the type of dies you talking about?

 

[racerone]

Hurry find a machine shop to repair this for you.------Your attempts with a die may well scrap that crankshaft.

 

[Chinewalker]

Are these the type of dies you talking about?

Yes. As Racerone pointed out, you may be better off having a machine shop clean those up.

 

[racerone]

Fact---The threads have been mushroomed.----The die may not pick-up correctly or even start.-You could wipe out / cut the good threads below the mushroomed area.--Find someone with experience in this type of work.

 

[spence88]

No Title

Update.
Took the boat to the shop. The mechanic told me the previous owner or someone tried to remove the flywheel but it was frozen on the crank. That's what caused the threads to mushroom.
But I bought a 1997 30 hp mariner to replace that motor. I'm still going to try and get that motor fixed.
I'll come back and update if/When I get that 88 fixed.



I'd like to thank everyone that took the time to help me and share your expertise.