[The Smoker King]

Hello all, my name is Aaron.

I am rebuilding a 1990 Evinrude 150 hp.

My question is on the cylinder bores; Cylinder number 2 is reading 3.524, all the rest are 3.501 or so after honing.

What should I do about this cylinder?

I appreciate your knowledge and input.

Aaron.

[Dhadley]

Welcome!!

We'd guess that #2 was already +.020 over and it took quite a bit of honing to make it look good, hence the .004 over. That one will go to .030 for sure. The rest measure extremely well, espicially given the age. .001 after honing is well within spec.

[The Smoker King]

I am really new to this, so when I get that cylinder to .3 over, do I also have to purchase a larger piston, or will the rings take up the slack.

[Dhadley]

Nope, you'll need a .030 piston. The rings will (should) come with it.

[Dhadley]

And (obviously) new rings for the 5 standard pistons. Assuming all 5 standard pistons are good / useable.

[The Smoker King]

Thank you for your quick reply!

I didn't know you could bore 1 cylinder only.

The rod bearings look pretty good. Would you recommend replacing them anyway, or is it okay to reuse.

Everything else looks good in the engine after disassembly. Only one piston is shot, (ring came apart), and the head is pretty dinged up. I may have to find a new one.

[The Smoker King]

Thank you for your quick reply!

I didn't know you could bore 1 cylinder only.

The rod bearings look pretty good. Would you recommend replacing them anyway, or is it okay to reuse.

Everything else looks good in the engine after disassembly. Only one piston is shot, (ring came apart), and the head is pretty dinged up. I may have to find a new one.

[F_R]

I used to bore probably an average of an engine a week, for all the other shops in town as well as our own. It was common to do just one or more cylinders. No problem, and believe me you can't tell the difference when it is running. And you can smooth off the high spots around the dings and re-use the head too. Just make sure you don't leave any chunks of imbedded metal in there.

[The Smoker King]

Originally Posted by F_R

I used to bore probably an average of an engine a week, for all the other shops in town as well as our own. It was common to do just one or more cylinders. No problem, and believe me you can't tell the difference when it is running. And you can smooth off the high spots around the dings and re-use the head too. Just make sure you don't leave any chunks of imbedded metal in there.

Music to my ears!! I will smooth out the rough spots. THank you too!

All bearings seem to be okay, which is great. Just the one piston failure.

[Dhadley]

Pistons rarely, if ever, fail by themselves. You need to find out what caused the damage to the piston so it won't happen again. If that cylinder was already oversize I'd bet the same thing happened to it before this time.

A damaged piston is a result, not a cause.

[F_R]

Agreed!!

[Solittle]

I have read several posts where it was recommended to replace all of the rod bolts on a rebuild and to make sure that they are torqued to spec.

[Dhadley]

If you're confident the rod bolts have only been used once, with no thread lock of any kind, they can be used again. If they're on their second trip, replace 'em.

If they have had any thread locker of any kind, toss 'em. And make darn sure you get all the remains of the locker out of the threads in the rods.

[F_R]

After having had a motor break a rod bolt 30 seconds after startup after a rebuild, I ALWAYS replace them. Overkill, maybe. But that rod sticking through the case wasn't pretty. Besides, it drew blood.

[Dhadley]

We've actually seen more new rod bolts break than "once-run" ones. It was a huge issue back in the early 80's, not so much anymore. When building a hot rod we measure the stretch of the bolt, new or not.