Crankshaft Questions

[arseaz06]

I have a 90HP, 1987 Mariner motor with serial number 9550004 at a repair site. The crankshaft has a few thin hairline scratches across where one CONROD sits. am told that the crankshaft needs replacing. I am in Africa and there are only a couple of marine repair shops. I am not sure if I am being taken for a ride or not. Pardon my ignorance as this is the first time I am dealing with engines. Does the crankshaft really need to be replaced. Any opinions about replacing the crankshaft is appreciated. Oziearseaz06@comone.co.zw

 

[OBJ]

Re: Crankshaft Questions

Hi Ozie....Welcome to the site. Hang around. You'll like it. First things first,,,no one is ignorant as no one knows it all and there are no dumb questions. <br /><br />To your questions - hard to say without seeing. Are the scratches on the surface where the bearings ride? Can you catch a fingernail on them? Sometimes a scratch can be cleaned up with emory paper and work fine. I have seen pitted journals cleaned up with paper and last and last. Can you get a second opinion? Maybe one of the other guys on site can help you more than me. Open for discussion guys.<br /><br />OBJim

 

[Hooty]

Re: Crankshaft Questions

What was the reason for the tear-down? Did it throw a rod? If not, and like ObJim said, if you can't feel it, and the journal is in spec, (proper diameter and no flat places)run it.<br /><br />c/6<br /><br />Hooty

 

[Gold Bear]

Re: Crankshaft Questions

Ozie<br /><br />Is the repair shop telling you the crankshaft is cracked - and that is the reason it needs to be replaced? If that is the case then they should perform an Non Destructive Test (NDT) either a Dye penetrant, or Magnetic Particle to show that the "scratch" is in fact a crack. I would recommend the Dye penetrant inspection in your case.<br /><br />Both test are easy to do, and inexpensive.<br /><br />If it is just a scratch then you have gotten good advice noted above.<br /><br />Good Luck,<br /><br />Gold Bear

 

[sloopy]

Re: Crankshaft Questions

if it ain't broke don't fix it! Hell forget it have fun...

 

[ODDD1]

Re: Crankshaft Questions

Ozie, you need to be picky when inspecting crank bearing surfaces...needle/roller bearings are unforgiving of surface damage, unlike a plain bearing used in a car engine...marks that go across the bearing, so a roller could 'catch' on the mark and slide instead of roll will eventually grow large enough to destroy the whole bearing.....the rule generally used is 'if you can catch your fingernail on the mark and feel it, it is a problem'...sanding/polishing the mark will not help. there is a very thin layer of very hard steel at the surface of these journals, any removal just speeds up the failure...now, I have seen damaged cranks run for years and years, and I have seen many rods hanging through the sides of motors from failed rod bearings.....if you use it over, you run the risk of failing a recently repaired engine with no one but you responsible for throwing more money at it.....

 

[arseaz06]

Re: Crankshaft Questions

Wow! This has been a tough one. Thanks for all the replys. I have talked to a few people here in the marine engine service business and they seem to think that it neds replacement. So I have decided to replace the crankshaft and buy what parts I need for the powerhead. DOes anyone know where I can buy remanfactured cranks?<br /><br />Ozie

 

[OBJ]

Re: Crankshaft Questions

Ozie...try the site below. There are many more places than whats listed at this site but it's a place to start.<br /><br /> http://www.marineengine.com/outboard_motors/parts/ <br /><br />Good Luck<br /><br />OBJim