Thorneycroft 108 diesel

[Guest]

Can anybody suggest what general overhaul work I should have carried out while my engine is removed from the boat for hull repairs?
Its a model 108, 1989, 4 cylinder, 38 HP serial number 6925.
I could do work on the top of the engine later, once its back installed but need to get any essential work that can only be done with it out and accessible, carried out by my yard now.
I've only just bought the boat and did not have an engine test and although the yard have maintained it for the last 3 years and say they dont know of any problems reported by the previous owner, at this age it must be worth taking the oportunity while its easy to get at.
Any suggestions please?
Malc Davis.

 

[ccscott49]

While the engine is out, it would be prudent to pull the sump and check all the main and big end bearings, crank, thrust washers, check cam followers and cam for wear, check oil pump and generally clean up inside. If any wear is found on the bearings, the crank might be worth putting a micrometer on and making sure uits within tolerances. I admit most of this work, if you are not an egineer, would require specialist equipment and knowledge. The bores, rings and pistons would also benifit from inspection, but if the bores are fine and the rings worn, the bores could be re-honed and new rings fitted. I would be tempted to have the short engine (block, crank etc) sent away for inspection, to any local engine man, doesn't need to be a marine engineer. All the rest of the stuff on the outside of the engine, can be looked at and re-furbished, whilst the engine is away being checked. One other thing which is often overlooked, is descaling of the internal water ways, aids cooling and consequently performance.

 

[chippie]

It would probably pay to have a look at the big end and main bearings, if these are scored or worn you can then decide whether the crankshaft needs to come out for regrinding etc. If this is neccessary it is probably worth replacing the piston rings while you are at it. Any rust showing on the exterior can be more easily dealt with while the engine is out. I dont have specific knowledge of this engine so these remarks are only of a general nature.

 

[Guest]

Re:\'member the mounts

Don't forget to check the engine mounts/blocks and any 'flex' material

 

[Gordonmc]

I am planning a lift out of my Thorneycroft 90, but an engine oil analysis came out favourable, so the beast will probably stay in for most of the coming season.
The motivation to take it out is to replace weeping gaskets and drop the sump. I am keen to get rid of the accumulated gunge I know will be in the pan. Unlike road engines most marine motors don't get a flush out at oil change because of the pump-out arrangement. You will be suprised at the bits of metal scarfe in the gloop.
If you have access to a compressor, give the oil-ways a good blast both ways. Don't forget to wear goggles. Give the oil rise gauze a good wash in paraffin
While the sump is off I would check out crank and bore wear although the latter would be obvious on running.
Consider renewing engine mounts, no matter how good they seem. Failure of the rubber to metal bind can't be seen until they part.
Have fun.

 

[superboots]

A simple job you can have done when the engine is out is to change the timing chain adjuster. On the 108 this is a primitive device which relies on a shoe and a spring. it can fail without warning and result in various bent pieces of metal. Accidential high reving of the engine could cause it to slip leaving you in the preverbial. (a common occurance for Sherpa van owners when having an MOT done)