Engine Identification

[normlee]

Hi,

Can anyone please shed some light on the model of this CMB 90? Any info would be great, thank you.

 

[Ron B.]

If I had to guess that is likely a motor from the early to mid 90's maybe an early GP motor. I never ran CMB's back then and I have only ever owned two, one of which is a 3.5 outboard and the other is a newer 90 size motor.

 

[Robert Pickard]

almost looks like the purple head hydro not sure

 

[wayne middlemiss]

Grand Prix 2

 

[moparbarn]

Grand Prix for sure. 4 bolt head makes it too old for a purple head hydro, Robert.

 

[francois peilleron]

This the 1992 or 1993 Grand prix model depending if your zimmermann disc has a drive dog(last for ever) or a off center rectangular hole;in this case you need to check if there is not too much clearance;I have a bunch of this engine ans as

BOAT MODELER wrote about this engine it is brutally solid and virtually indestructible,check sometimes if the ball bearing clip

is not too loose;if you take care this engine last for ever

 

[normlee]

Thank you for all your help, I bought this engine and it came with a new piston and sleeve to put in it down the track. Does anyone have a parts breakdown or instructions please, never pulled down a CMB engine before.

Thanks heaps,

 

[Andy Brown]

Most parts from mids 80's to about 2003 versions will interchange. The RS and RS Evo versions of the last 10 years have little in common.

Lots of good used parts out there. May be very difficult to find new parts.

 

[Tom Kelly]

Thank you for all your help, I bought this engine and it came with a new piston and sleeve to put in it down the track. Does anyone have a parts breakdown or instructions please, never pulled down a CMB engine before.

Thanks heaps,

If it's like the newer RS engines, you need to pull the wrist pin out through the exhaust port. The I.D. of the wrist pin is threaded, so you can screw in a long screw to pull it out. Once you have the piston and sleeve out, you should be able to wiggle the crank assembly out.

 

[DaveThynne]

Im 99% owned that engine 18 months ago. Its an early gp90 engine. It was solid! Keep the exhaust throttle, itll be a lot better than the slide carb that i sold it with. it has a modified liner in it with okay compression. Keep the new one aside in case you have a failure with the current piston liner. You will get new bearings once you tear it down and get the size of the bearing. Maybe someone else can help out? Everything else in the engine is virtually indestructible.

 

[normlee]

Thanks for the info, I bought this engine with a twincraft 46" mono, came with the original back plate and carby and a gardner exhaust throttle. When I removed the exhaust throttle found that the top pinch bolt had been way over tightened and distorted the port. I have a "Looking For" advertisement in the for sale section now.

Appreciate the info,

Regards, Norm

 

[Ron B.]

Im 99% owned that engine 18 months ago. Its an early gp90 engine. It was solid! Keep the exhaust throttle, itll be a lot better than the slide carb that i sold it with. it has a modified liner in it with okay compression. Keep the new one aside in case you have a failure with the current piston liner. You will get new bearings once you tear it down and get the size of the bearing. Maybe someone else can help out? Everything else in the engine is virtually indestructible.

Bearing's for the CMB 90 GP are a 6001 and a NK12/12 Needle Roller.