Down the auto vs. marine road once again

[Nappy426]

I know the auto vs. marine topic has been brought up more than once, and apologize, but I can't find anything on the finer parts of the motor such as rings and bearings. I detonated my Yamaha 4.3 a few weeks ago and am looking at a complete rebuild, since I have it torn down anyway. After pricing parts at my local Yamaha dealer, I realized it would probably be cheaper to just buy a new boat. They wanted $119 for rings, and that was per piston. Not to mention bearings and gaskets. I know corosion plays a large part in a marine motor. Since rings and bearings don't see water anyway, I don't see why an auto engine ring and bearing kit wouldn't work. I am looking at a heavy duty kit that is normally used for racing motors to take care of the high rpms of a marine motor. I am also having to get the heads rebuilt since the valves colapsed in 3 cyl. and are starting to in the other 3. Is there a difference in auto and marine valves? Any clarity would be helpful so I don't end up learning the expensive way.

 

[Laddies]

Re: Down the auto vs. marine road once again

Most auto supply firms have listigs on marine engine kits if you can get them off their thumbs and all NAPA stores do

 

[Bondo]

Re: Down the auto vs. marine road once again

Ayuh,.......<br /><br />Quality Rings,+ Bearings are Just That...... No Marine stuff there.....<br /><br />Nowadays,.... Same goes for Gaskets.........Steel Shim headgaskets are Out,+ Composites are In......<br /><br />You Could go to a Fancy set of Valves,.... But,.. Production valves will do All that You Need........

 

[ron7000]

Re: Down the auto vs. marine road once again

the only 'finer' points I've come across are that piston ring ends gaps are a little larger in a marine motor than auto because they run under a much greater load for longer periods and generate more cylinder heat. I think for the typical 4" bore end gap is around 18-20 thous inch for automotive and around 30 thous for marine, but it also largely depends on what the ring manufacturer recommends because of what material they make it out of and can also be affected by piston material and design. And another common thing are stainless steel valves in the head but I don't believe they are a necessity. And like bondo said, composite head gaskets are better but that can be because of salt water raw water cooling. If you have fresh water cooling than it's a non issue in terms of corrosion so then any quality head gasket would do.<br /><br />$119 for one piston worth of rings is wrong, the dealer is screwing you. check jegs.com have your piston diameter and get a set of moly rings for eight pistons for $109.

 

[Nappy426]

Re: Down the auto vs. marine road once again

Thanks for the info. I started calling local parts houses today, pricing rebuild kits and came across another question. When the first guy asked me if I had a balanced crank, I was kind of stunned. First thought was well duh. try spinning a metal shaft at 4800 rpm and you tell me if you think it is balanced. I told him I didn't know, but would find out and call him back. After the third guy asking me the same question I began realizing it really is an issue. How can I tell if I have a balanced crank or not. FYI I have a yamaha 4.3L V6. Any help would be appreciated.

 

[Bondo]

Re: Down the auto vs. marine road once again

What they're talking about is the Later model 4.3ls that have a 3rd Shaft,.......<br />It rides above the Cam in the lifter valley,+ is driven from the cam drive........<br />The Top of the Timing Chain Cover will have an Extra Hump in it......<br /><br />I'm not sure of the Year of the model Change,.......

 

[Gary H NC]

Re: Down the auto vs. marine road once again

Bondo, didn't they start using the balance shafts around 1990?