Yamaha 1992 90HP overheat - possible impeller?

[ausnoelm]

So tried to descale today but still no luck, bit the bullet and pulled the exhaust plate off but snapped three bolts, one is accessible but two down the bottom would either need a hole drilled through the cowling or pulling the power head to remove.
I’m sure this is my problem as there was so much crud and bits of broken old impeller from who knows when in there. Am cleaning it up now but thinking of how to remove these bolts.

one thought I had was given the low torque value would just sealing the holes with permatex no1 be ok? I think this will be the last time this job will be done for this motor before it becomes an anchor for a four stroke upgrade in the next year or so.

Not too sure you will get away with missing bolts, but you might. Doesn’t the lower cover come off that model for access?

[Vasilako]

Not too sure you will get away with missing bolts, but you might. Doesn’t the lower cover come off that model for access?

No unfortunately the cowling is all one piece, also given how corroded the bolts are in there and hardly anything to grab am hesitant to try an EZ out to remove them.

[Vasilako]

They are the three that broke off

[ausnoelm]

The couple with a bit sticking out might be OK, can you weld? Tacking a nut on to the protruding bit sometimes works, the heat from the weld will help with the bolt corrosion. Not too sure you will get a good seal with those bolts missing, but who knows?

[Vasilako]

Unfortunately don't have access to a welder so that's out, got quoted about $800 by someone to remove the three bolts which I really don't want to pay lol

[ausnoelm]

Be VERY careful with an EZ out, when (not if) you break that off, you’re done……the power head is coming off. Very carefully drilling, on centre, and straight, with a very sharp, quality drill bit, slowly increasing in size is you best option, even better if you can buy some left hand bits! in time you will be able to pick out the broken bits of thread.

[panasonic]

The two sticking out maybe saved yet. Try to file two flats on them so you can get a good grip on them with a good pair of vise grips. Then put the heat to them with a propane torch. Heat and let cool several times before trying to turn them.

You will need a file with a safe edge on it ( no teeth on one edge) so you can put the file on the aluminum and not damage the sealing surface.
You can make your own safe edge file by grinding off the teeth on one of the thin edges.

Easy outs are not your friend.

[panasonic]

If you can get two out you maybe in good shape to leave the very bottom one alone. If it drips a bit that won't hurt anything. Use a good gasket sealant. You got nothing to lose at this point!

[Vasilako]

The two sticking out maybe saved yet. Try to file two flats on them so you can get a good grip on them with a good pair of vise grips. Then put the heat to them with a propane torch. Heat and let cool several times before trying to turn them.

You will need a file with a safe edge on it ( no teeth on one edge) so you can put the file on the aluminum and not damage the sealing surface.
You can make your own safe edge file by grinding off the teeth on one of the thin edges.

Easy outs are not your friend.

I might give this a go once the weather clears here in Sydney going out and spraying with some penetrating spray in the meantime...thanks for the tips and help everyone!

[Vasilako]

had no luck removing the bolts, so I ended up using some JB Weld Red RTV around each bolt between the new gaskets, then some JB WaterWeld to plug the bolt holes on the cover. Let it cure for 24 hours and gave it a test run this morning on the muffs.....

Had a small leak from Bolt 13 which is the lower bottom bolt, but had no way to put my torque wrench on that one, tightened her up and ran for a good half an hour....no leaks!!!

Telltale is now how it should have been...strong flow so hopefully I have fixed it all up.

Pulled out the bottom spark plug after running to see if I could see any water ingress but all looked good

I know it's not the prettiest repair job, but if it gets me through to motor upgrade time I'm happy with it.

Once again, thanks everyone for your suggestions and help on here! Have learnt a great deal given that this is my first ever boat (only picked up the boat in October!)

[panasonic]

Sometimes good enough is good enough! Not like there is any great pressure in there anyway. If it leaks a bit it's not going to make much difference.