Just startine Rebuild on 89 yama 200hp

[Restretch34]

hey,<br /><br />i'm starting a rebuild on my 89 yamaha 200hp and wanted to know about any tip or tricks out there.<br /><br />Also, the dealer said i needed to replace the cranks rings because of age. Just curious if this is critical.<br /><br />thank<br /><br />ken

 

[rodbolt]

Re: Just startine Rebuild on 89 yama 200hp

why does it need a rebuild ?

 

[Restretch34]

Re: Just startine Rebuild on 89 yama 200hp

Compression is going down on one cylinder and there is a variance of over 10lbs. The compression is 113,109,110,104,101,106. I just thought a little preventative rebuild would save a blown powerhead later down the road.<br /><br />Thanks <br /><br />Ken<br /><br />ps the 101 cylinder at the begining of boating season was 103

 

[rodbolt]

Re: Just startine Rebuild on 89 yama 200hp

I would do a good decarb then rerun the test. those numbers may or may not be that bad,<br /> when compareing numbers on the yamaha compare them bank to bank,ie 1-2 3-4 and 5-6. but if you wish to rering it carefullly measure the bores after honing to insure the piston to wall clearence remains in spec. this will require both careful bore measurements and careful piston measuring. always use new rodbolts and wristpin circlips. I always replace the bottom main bearing anytime the block is apart, the others may be reused if inspection shows no defects. I have never heard of replacing the crank seal rings as a routine issue. if they are not damaged they are reusable.<br /> after a decarb a leakdown test will tell you if the cylinders can seal. if your in saltwater you may find the shift shaft is rusted so remove and check it while the power head is off.