Need help(79' 50hp seahorse)!

[andy6374]

Re: Need help(79' 50hp seahorse)!

Originally posted by ezeke:<br /> <br />I see the 03 stamp on the piston, so you can't take much risk with that block.

I am not sure if I follow what you are getting at. Are saying the block might be damaged in some way?<br /><br />I'll be removing the exhaust cover to get a better look at the rings.

 

[ezeke]

Re: Need help(79' 50hp seahorse)!

No, I'm saying that the engine has already been rebuilt with larger than standard pistons. If you have a bad ring and later score the cylinder, you may not be able to bore it out again.

 

[Chinewalker]

Re: Need help(79' 50hp seahorse)!

I see an "UP", but no .030. If the piston is oversize, it'll have the size on the piston crown. <br /><br />With no visible of notable scoring, it might be in need of a decarboning. Much info here on the site on the methods and products to use.<br /><br />Invest in a new head gasket before reassembling...<br /><br />Be generous with the throttle on start-up. Those big-bore Johnrude twins are cold-blooded creatures and like the throttle set fairly high on cold start. Be prepared to back it down so it doesn't race away from you. <br /><br />- Scott

 

[ezeke]

Re: Need help(79' 50hp seahorse)!

My mistake, Chinewalker. <br /><br />Sorry Andy, didn't mean to cause you concern but I did misread it.

 

[andy6374]

Re: Need help(79' 50hp seahorse)!

I hope it is a stubborn stuck ring. I should have tried decarbing before pulling the cylinder head but I was convinced of worse news. This was because the engine wouldn't even attempt to start (it only started once for about 5 seconds). <br /><br />If I decarb, get a new head gasket and there is still weak compression on the bottom cylinder can I reuse the new head gasket (since I will have to remove it again)?<br /><br />Well while I was at it I was going to pull the exhaust cover to inspect the rings on the bottom cylinder. Hopefull I don't get any more broken bolts. But perhaps I should try a decarb before getting myself in more trouble.

 

[andy6374]

Re: Need help(79' 50hp seahorse)!

One more thing...<br /><br />With the cylinder head I can see that the tstat and gasket as well as the pressure relief valve/grommet/spring need replacing ASAP. The BRP website says the tstat (OEM 0378065<br />) is unavailable, but sierra carries it (18-3553 or kit as 18-3672). But the BRP site says I can't get the pressure relief valve nor the spring and the sierra doesn't carry it either, so what do I do. I will check the local dealer but chances are they don't have it.

 

[ezeke]

Re: Need help(79' 50hp seahorse)!

Thermostat OMC 378,065 is superceded by OMC/BRP 5,005,440<br /><br />Pressure Relief Valve 317,653 is superceded by 335,493<br /><br />Spring for Rope Start model is 322,841<br /><br />Grommet is 316,132<br /><br />Gasket is 310,058<br /><br />All (or superceding part) are listed at ishopmarine.com for one, but I cannot think of a reason why any J/E dealer cannot provide them.

 

[andy6374]

Re: Need help(79' 50hp seahorse)!

thanks ezeke-<br />The reason I said that the J/E dealer won't carry them because some of the parts are listed as SA 7 which means they don't even produce that part # anymore, but if they were superceded by new part #'s that is probably why.<br /><br />I will go pick em' all up.