GM V8 diesel now running

PCUK

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Thanks for all the advice, bought the manual on disk, bled the engine according to advice here and in the manual and got it to fire a couple of times. As it has been standing for about four years decided to give a sniff of Easy Start and after a couple of coughs off it went.
Warmed up and then started on its own. All instruments worked - amazing as they are half full of condensation and even the volts came up showing some life in the alternator.

Just got to make sure it will start properly from cold and then it can be lifted for cleaning and leak checking and to change the ancient OMC drive for something a little more modern!
Thanks again for all the advice.
 

Mr Googler

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I just pulled them out and turned the key to prestart briefly and saw if they glowed. 6 did, 2 didnt. Only about £18 each if I remember. I dont think you would feel them getting hot in situ but I could be wrong. No doubt more knowledgable formites will be able to advise on testing the strength of the "glow" but for me, all of them glowing improved things :)

Its just a spade connecter onto the end so they can rot there too. Easily enough to get to them depending on your manifold design.
 

Latestarter1

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Thanks for all the advice, bought the manual on disk, bled the engine according to advice here and in the manual and got it to fire a couple of times. As it has been standing for about four years decided to give a sniff of Easy Start and after a couple of coughs off it went.
Warmed up and then started on its own. All instruments worked - amazing as they are half full of condensation and even the volts came up showing some life in the alternator.

Just got to make sure it will start properly from cold and then it can be lifted for cleaning and leak checking and to change the ancient OMC drive for something a little more modern!
Thanks again for all the advice.

Just take a step back.

OK, the GM's hard to take seriously but you are enjoying playing. Please please do not start spending serious $$ on a decent leg to go behind this motor, just cash down the drain.

Check and see if a lube oil cooler has been fitted, engine will have life of a disposable cigarette lighter without one.

I have been closely invoved with several of these monsters. The first was a pair fitted a Princess belonging to the Captain of British Airways 737 which suffered a fatal fire on take off in 1995, the poor guy was never in good shape after the accident. However after $$$ had been spent I had to be the one who broke the news that engines would never work. Second vessel was another gas to diesel Samuarai conversion which also nearly broke the retired owner. Only a significant award from Exeter County Court which partly funded fitting a Steyr saved any more heart ache.

Boating should be for pleasure not an ounce of pleasure in a GM V8....
 

PCUK

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Thanks for comments LS.
This isn't a petrol to diesel conversion, not sure what you were working on, but according to the history of GM and these engines they were designed from the outset as diesels during one of the fuel crisis, so it's a GM 6.2 diesel from the outset.
I realise Samurai were **** converters, but there are millions of these in trucks and military vehicles so the base lump isn't bad.
Yes, it has an oil cooler, plus a good quality off-the-shelf heat exchanger, the water-cooled manifolds are Samurai and are in good condition, but when they need replacing I'll make my own.
Rebuild costs for these engines is low and remanufactured blocks are less than two grand without an exchange so I can't see any big or expensive problems, but I'm willing to be convinced otherwise.

Ought to also mention that the ancient OMC leg (rack and pinion steering and trim and tilt - so very very old) has to be replaced regardless of the engine so whatever happens it won't be money wasted.
Another point is that the boat cost next to nothing and I will be doing a total top to bottom, inside and out renovation so I can afford to take a chance on the engine at this stage.
And I do appreciate your advice.
 
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Divemaster1

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Thanks for comments LS.
This isn't a petrol to diesel conversion, not sure what you were working on, but according to the history of GM and these engines they were designed from the outset as diesels during one of the fuel crisis, so it's a GM 6.2 diesel from the outset.
.........

Think LS meant that the GM 6.2 / 6.5 were often used as re-engine diesel alternatives for V8 petrols... the dieselised petrols were very diferent indeed (Google "toroflow"). The GMC trucks did have these 6.2 / 6.5L's as alternatives. Engines worked well in light to medium applications, but were never designed for heavy loads... In a light planning boat, these engines can work well, but two things are essential;

1) Marinising must have good cooling capability and do need the oil cooler LS mention
2) Never.... and I do mean NEVER !!!!! overprop the engine !!! it just is not designed to take high loads for prolonged periods ... which you will find on a boat, and particularly when over propped...

Parts should be readily available for these engines and as you point out are relatively cheap, but be aware that not all parts are interchangable between the 6.2 & 6.5, but people think they are the same engine, so be sure you get the right parts for your engine...

Good luck!!
 

Mr Googler

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FWIW I think Latestarter1 is a true expert.

That said it sounds like your project is currently pretty cheap.

I think its a matter of expectation. No doubt the gm was never designed for marine environment hence why the marinisation components are so important in an effort to combat some of the demands. Mine was a first class marinisation with the components surrounding the engine accounting for more value than the engines themselves!! I would still say that I never had total confidence in the engines. They ran and we got 30 knots but it always seemed an effort and a bit strained. The torque is big and again I always worried about the legs being up to it.

I also appreciate they are cheap but the question is why can you get a short block for £1500. I would imagine because the demand is there due to high failure rates and commonality.

You sound mechanically minded, as am I, but I was disappointed in never having faith in the engines and therefore never using the boat to its full potential as in long trips with the family.

Sounds like its not going to be worth spending yanmar money so I guess its just a suck it and see. Perhaps invest in an outboard as backup. Say a 250hp honda :)

Funnily enough, I looked at a princess 330 with twin petrols the other day and looked at marine diesel in Sweden who use GM blocks for their marine engines. Looks good on the outside with purpose made components etc... but a few forums later and all does not look well :(

I wish you the very best with the project but have one complaint.....no pictures...poor, very poor :)
 

PCUK

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Far too soon for pics, but I'll get round to it.

Divers comments are interesting and somewhat reassuring as the boat is a lightweight 25ft Reinell.

I can't believe that an engine can be in production for so long and be no good at all.

Although a pre 1992 model this engine was installed in 2005 so should be a new ex-military unit as that was what Samurai imported (if my research is correct!).
If so it has done less than 100 hours and if I look after it, it should be OK.

What I need to do now is start a new thread and find out just how many of these lumps are actually in use in boats and how well they stand up.

Thanks again for all the input.
 

Divemaster1

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.......I can't believe that an engine can be in production for so long and be no good at all.

......What I need to do now is start a new thread and find out just how many of these lumps are actually in use in boats and how well they stand up.......

Let us get a couple of things straight....

1) Engine is OK for it's intended purpose ...light to medium trucks...
2) Engine was never well received in the UK Marine applications.... mostly du to incorrect application and poor marinising....

You will find a greater user base in Scandinavia where Peninsular did the conversions...

Some more stuff on various forums..... but will never be one-sided ... or entirely positive.... as the engines did have weak areas ... more in the 6.2 than the 6.5....

Reliability is linked to output & demand ... between 100 and 170 Hp these lumps should be very reliable indeed (if that is enough for you, then de-rating shold be considered). At 260 ... very much less so... very much the same as the newer engines .... Commercial ratings are much lower than leisure ratings for same engine ....
 

PCUK

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Thanks Alf,
This is 160hp naturally aspirated so not unduly stressed for a 6.2 litre.
I'm going to start a new thread tomorrow about how engines get their bad reputations. Glad to see you there!
Cheers,
Peter
 
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