piston to cylinder clearance, need to know!

[yamahasteve]

he all, rebuilding my 9.9msh from 2006, got .5mm over bore pistons. was wondering if anyone knows what the piston to cylinder clearance is or preferably they have a service manual for this engine and can tell me exact specs?? thanks!

[almetelo]

[scofflaw]

consult with the piston manufacturer, not all pistons call for the same CLEARANCE

[yamahasteve]

OMG thank you for the pic. where did you get that? pistons are from Yamaha, not aftermarket like Wiesco.

[yamahasteve]

Can you confirm for me that this is for a 2006 9.9msh? sorry to be a pain

[boscoe99]

Looks to be from SM LIT-18616-02-59 which is the SM for a 9.9MSH.

Why are you rebuilding a motor without having a Yamaha service manual on hand? There is much more than just piston to cylinder clearances to be concerned with. Torque values (pound-feet), torque sequence, sealants, assembly order, cylinder taper limits, piston ring end gap clearance, crank shaft run out, etc.

[ausnoelm]

Biggest concern for me would be whether the people who do the machine work know anything about 2 stroke outboards.

[scofflaw]

A good machinist doesn't need to know about 2 strokes. He needs to know the specs and what parts you want cut, and whether or not he has the tools to do the job.

[ausnoelm]

OH, is that so? OK then, just checking........

[99yam40]

A good machinist doesn't need to know about 2 strokes. He needs to know the specs and what parts you want cut, and whether or not he has the tools to do the job.

If they do not do 2 stokes all of the time and know how to releave the ports after boring, then find a shop that does.

A shop that depends on the owner knowing what the shop is suppose to be doing and telling the shop how or what to do, is a bad shop to be doing the work

[scofflaw]

You bring your stuff to a machine shop... Your in charge and YOU tell them exactly what you want done.

Engine builder.... You drop your stuff off and pick it up when it's ready.. they do whatever THEY think should be done.

[ausnoelm]

So then, let's just for a second, think that you don't know exactly what needs to be done, and your machine shop just does "what you ask" they know what they are doing, because they do hundreds of car engines, so it will be OK.... 2 stroke bores are NOT car engine bores.

[boscoe99]

This reminds me of many years ago when my Mercury EFI would not go over about 2000 RPM. I was a hundred miles from home. Left the boat and motor at a Mercury dealer and thought I was crystal clear to him that he was to only trouble shoot the problem and let me know what the fix was. If cheap I was going to let him do it and if expensive then I was going to do it.

The basturd called me a few days later to say the motor was repaired. $900 bucks as I recall. WTF. He installed a new Mercury stator. I would have used a CDI one. We went round and round about him not being authorized to repair the motor. He was only to trouble shoot it. We settled by him letting me have the Mercury part at his cost.

I pick up the boat and take it to the lake. It runs fine now. I lifted the hood. The basturd had removed the detonation module. I had to go back to his shop to get it. He said it was not needed. WTF. Over.

Either the dealer was not listening, did not want to listen, or did not care to listen.

In conclusion, one has to be careful when dealing with other folks to repair their stuff. Tell a mechanic to put new plugs in to solve a stalling problem but don't blame the mechanic when he changes the plugs and the problem is still there.

[rodbolt17]

machine the cyl like a 4 stroke.
your going to do pistons twice.

[scofflaw]

So then, let's just for a second, think that you don't know exactly what needs to be done, and your machine shop just does "what you ask" they know what they are doing, because they do hundreds of car engines, so it will be OK.... 2 stroke bores are NOT car engine bores.

Exactly right, if you don't know exactly what you need , don't drop it off at a machine shop.