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Old 18 October 2011, 07:22   #1
Country: UK - England
Town: Portsmouth
Make: Ribcraft
Length: 5m +
Engine: 60hp and 50hp
Join Date: Oct 2011
Posts: 1
Big End Bearing Crisis

Hello All

An alarming knocking noise started coming from within my engine, and on closer inspection the big end bearing had collapsed on piston no.3. The crank shaft journal is also scoured, and needs to be ground/polished to return it back to usable condition.

The engine in question is a Mariner engine model no 60PT4S from 2005, 60hp, 4 stroke, EFI and Bigfoot gearbox.

So far I have done all the work disassembling the block to remove the crank, and have found a company that will regrind the bearing, but I need to be able to find out if Mariner produce oversized bearings, and if so what tolerances they have. I have so far had no luck getting any information about these. Can anyone please help?

There is another possibility however. Does anyone have an identical crank shaft for sale?

Thanks in advance


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Old 18 October 2011, 08:32   #2
Country: UK - England
Town: Lancashire , Scotland
Boat name: TARKA
Make: Humber Destroyer
Length: 5m +
Engine: 3.3,75
Join Date: Jun 2011
Posts: 196
Originally Posted by Moomoo View Post
Hello All

So far I have done all the work disassembling the block to remove the crank, and have found a company that will regrind the bearing
Hi , I am assuming this should have said crank.

I have had a similar problem in the past , A local Engine Remanufacturing Company Was able to Match me up some bearings that were Undersize, I just took them the Block(for main Bearings) ,Con Rod crank and old bearing, they only regroung the crank , then matched them up.

If you go on and register

You can get part no's etc , they do list 3 big end bearing numbers for your model engine (Depending on serial number) .

These may be different sizes , I do not know , but worth a look.


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Old 18 October 2011, 12:36   #3
Bigmuz7's Avatar
Country: UK - Scotland
Town: Glasgow
Boat name: stramash
Make: Tornado
Length: 5m +
Engine: Etec 90
Join Date: Feb 2006
Posts: 5,068
Many manufacturers should do 2 or 3 sets of shells thicker than the originals .. (well they certainly do in my line of work) or the guys grinding the crank should be able to source similar ones. The only problem is how badly damaged the crank is, (did it get heated?) because sometimes it needs grinding beyond what the thickest shells will take, and is thereafter known as...... 'fecked'
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Old 18 October 2011, 14:43   #4
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 913
before you go to far i would recomend that you give the service manager a ring at barrus (ask for the obm service manager) or if you are freindly with a merc/mar dealer ask to have a look in the service manual the job could get complicated, good luck
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Old 19 October 2011, 17:03   #5
Country: France
Town: La Gaude - France Cote d'Azur
Boat name: Grey Cat
Make: Stingray South Africa
Length: 6.3 catamaran
Engine: 2x Yamaha 90hp
Join Date: May 2004
Posts: 9
I remember having seen this kind of repair 30 years ago, it was on a racing car crankshaft.

High strength steel had been added to the defective surface by projection (plasma ...?) then ground, the final surface was harder than original, with an identical diameter.

Possibly check this !
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Old 20 October 2011, 04:22   #6
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,650
When I did my pistons both the Mallory & Sierra Marine catalogues had all sorts of over & undersized stuff at about half the price of the OEM kit.

They also did a "special" on Pistons for when you had reached the point that +0.030" was not going to cure it. Not sure if they do that for bearings.

Just a note - type Sierra Marine into Google or you'll get 50,000 pages about a certain Ford car form the 1980s...

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