Mercruiser 470 alignment cause crank bearings to fail?

[JasonJ]

The saga of the friends Tahiti continues. I had removed the Mercuiser 470, put new rings and bearings in, and reinstalled motor. I had left the front mount on when I removed the motor, so when reinstalling, I shouldn't have needed to realign it should I have? There was no noise issues with the drive train, it had all went together easily. The problem is the motor ended up eating the crank bearings, and I removed the motor again and we sent it to a shop for a proper rebuild of the short block. The mechanic said if the engine wasn't aligned, that could have ruined the main bearings, but I am not quite buying that. I would think the coupler would get toasted before an engine problem would occur. I think the bearings were ruined because we just didn't do a proper rebuild in the first place. Any thoughts would be appreciated, as when the motor is done I think either a shop should reinstall and align, or at least I need to find an alignment tool so I can make sure that is fine.

 

[Wellcraft 89]

Re: Mercruiser 470 alignment cause crank bearings to fail?

I think your assumption is correct!<br />If you change gimble bearings or remove engines you should use an alignment tool.But i've done what you did years ago and never had a problem. <br />Get your own alignment tool it's $100.<br /><br />Just My$.02<br /><br />Rich

 

[MrBill]

Re: Mercruiser 470 alignment cause crank bearings to fail?

JasonJ: My vote is with you...the bearing issues are the result of improper rebuild. You don't mention your experience...but I learned the hard way that proper re-conditioning of the crank and setting the bearings is critical. The first 4 engines I rebuilt failed due to spun bearings, then I began to use plastigauge for measuring bearing clearace, then finally began having lowers more accurately done at a machine shop...no bearing failures since.<br /><br />My advice is to have the lower done at a shop, other machining too. An alignment tool wouldn't hurt either after you've gone through all the other hassle.

 

[JasonJ]

Re: Mercruiser 470 alignment cause crank bearings to fail?

I have years of automotive experience, and a lot of outboard experience, as well as anything with an engine. My friend was hoping to save a few bucks, and I had warned him that without having the crank journals ground and appropriate oversized bearings put in that he may be urinating in hurricane force wind, but he is having a shop do a proper shortblock rebuild now. I personally feel that the alignment is very close, but I am going to see if I can beg or borrow a tool and align it to be sure. The fact that everything went back together the first time easily and there were no horrid noises or damage to the coupler tells me the alignment is close. I really do not have $100 to burn on a tool I will have little use for. I personally would never own an inboard boat, outboards are just a more logical way to go, and I do not repair boats for a living, I was just trying to hook a friend up. I have wondered though why I couldn't get the specs for the tool and grind one on a lathe, I am sure I know someone with one of those.

 

[rodbolt]

Re: Mercruiser 470 alignment cause crank bearings to fail?

if you can turn one on a lathe I will be happy to send you the diminsions. I will measure mine and send it on. <br /> I can try to send a crude drawing as well<br /> Good luck

 

[denniz]

Re: Mercruiser 470 alignment cause crank bearings to fail?

engine/ drive alignment has Nothing to do with a bearing failure, thats a crock of sh--. Coupler would have spun.

 

[JasonJ]

Re: Mercruiser 470 alignment cause crank bearings to fail?

Rod Knocking, thats exactly how I felt. I talked to my friend who owns the boat, and the mechanic has since also concluded that alignment issues would not have caused it. The mechanic also said that everything I did to the motor was fine, there was no reason for the main bearings to eat themselves, he said it was just one of those things. Now they are doing a full engine rebuild and I will install it when complete.<br /><br />Rodbolt, yeah if I can get dimensions I can whip one up. I know a few people with lathes, I can just go get some steel and run one out.

 

[rodbolt]

Re: Mercruiser 470 alignment cause crank bearings to fail?

hello jasonj<br /> I will try to send them tomorrow<br /> its a simple tool<br />and I agree. drive alignment wont cause bearings to fail on the crank. however grinding dust/debris from a fresh turned crank that was not properly cleaned will eat them out in a few minutes. this I have seen many many times. while rebuilding and reassembly blocks and heads cleanliness is not next to godliness. it is absolutely mandatory.<br />if you did not scrub it at least 3 times odds are it was not clean.<br /> I use hot water for the final rinse on metal parts,get it as hot as you can with the water then blow it dry. if the metal is 120 degrees or so the water will evaprate instanly. then scrub everything with lintfree rags and engine oil.<br /> good luck and try to find why the bearings ate them selves. or it may do it again

 

[JasonJ]

Re: Mercruiser 470 alignment cause crank bearings to fail?

I don't have to worry about the rebuild, a shop is doing a full rebuild on it. That way there is a warranty and we know it is done right. What I did was the ghetto backyard (well, garage) Jethro shadetree style replace bearings and rings. Not optimal, but that was what the budget allowed, despite my warnings. Now he is out the cost of what I did AND the cost of a rebuild. Lessons learned.

 

[rodbolt]

Re: Mercruiser 470 alignment cause crank bearings to fail?

hello<br /> sorry I have not sent the tool diminsions yet. I have been in and out and chasing all over. we are trying to move all the marina boats and all kinds of crazy things just to watch a storm miss us again. I will try to measue it tomorrow and post it. its a simple tool<br /> not complicated at all<br /> good luck

 

[JasonJ]

Re: Mercruiser 470 alignment cause crank bearings to fail?

Thanx. Take your time, I won't need it until October. I am fairly sure the tool is similar to an automotive clutch alignment tool, just longer.

 

[rodbolt]

Re: Mercruiser 470 alignment cause crank bearings to fail?

hello<br /> yes it looks similar only about 3 feet long and no splines<br /> one OD for the coupler and one OD for the gimbal bearing<br />I will get it tonight<br /> looks like this storm coming is gonna be a big one. if it hits it will make a mess here.<br /> well start with a piece of solid stock 1.375 diameter. turn it back 2.145" at a diameter of 1.008" the next OD will turn back another 2.765" at 1.153" the overall length of the tool is aproximatly 26". you may wish to add a 1/4 in lengthh to the first linear diminsion. the newer v8 couplers have grease fittings that hit the first shoulder. the first OD fits the shaft coupler and the second fits the gimbal bearing.<br /> good luck