Ailing mercruiser 120 hp

nik · 08 April 2007, 20:16

Hello all,
My poor old diesel has gone sick on me.
I was out today, had a good cruise around and was heading back home when I lost power. The engine still runs, but only up to 1800 rpm.
I was doing 30 knots, I gave the throttle a nudge for a bit more speed, then I heard a noise like a tube suddenly deflating, and then I lost power.
I thought maybe a airhose had come loose on the turbo, but I couldnt see anything amiss.
As this is a mechanical injection pump, I am puzzled why I could only reach 1800 rpm.
I have a suspicion that the turbo may be knackered, which doesnt bode well for reliability.
Any suggestions are welcome as to what the problem may be, also, any reccomendations for mercruiser mechanics in the chichester area?

Thanks, Nick.

alt · 08 April 2007, 21:58

My opinion:

Your turbo has gone dead. Probably due to a seized wastegate. When you tried to give the engine that bit more throttle, you over-boosted.

Common problem with this engine. Contact Cummins ASAP and argue your case, it's a known fault with them yet they never recalled the engine.

Here are some links:
http://rib.net/forum/showthread.php?...&highlight=1.7

http://rib.net/forum/showthread.php?...&highlight=1.7

http://rib.net/forum/showthread.php?...&highlight=1.7

nik · 09 April 2007, 10:27

Thanks Alt.
I would have thought overboosting would do more damage to the engine than the turbo.
I am also puzzled by the noise it made when it went.

Nick.

alt · 09 April 2007, 10:45

Quote:

Originally Posted by nik

Thanks Alt.
I would have thought overboosting would do more damage to the engine than the turbo.
I am also puzzled by the noise it made when it went.

Nick.

You may have been lucky and a hose could have blown off before doing damage to the engine, or even turbo.

I take it you've inspected the whole engine for anything of the likes?

nik · 09 April 2007, 12:38

I have only had a cursory look, not helped by the fact that I am not overly familiar with this engine.
The other thing is, why could I only manage 1800 rpm no matter how far I pushed the throttle.

Nick.

Alan · 09 April 2007, 13:35

Quote:

Originally Posted by nik

I have only had a cursory look, not helped by the fact that I am not overly familiar with this engine.
The other thing is, why could I only manage 1800 rpm no matter how far I pushed the throttle.

Nick.

Some sort of 'limp home mode' governed by the ECU?

nik · 09 April 2007, 13:59

Quote:

Some sort of 'limp home mode' governed by the ECU?

Mechanical as I understand it, no ecu.

It would seem that the waste gate valve can be a problem on these engines, if it suddenly opened, that could account for the noise. Or it could be some of the air hose has come adrift. But the engine should still rev.

Nick.

calum mckenzie · 16 April 2007, 22:22

Hi Nik two of my friends had the same problem with the exact sympoms that you have described, the fault was the Turbo, the waste gate was seized wide open, the problem was getting a new turbo at a reasonable cost as the mercrusier price was over £1000 ! trying the well known turbo suppliers brought down the price unfortunatley they were on back order last year with a 6 month wait so they had them repaired at a cost of around £400 they came back as new and work a treat.
regards
Calum

alt · 16 April 2007, 22:50

Quote:

Originally Posted by calum mckenzie

Hi Nik two of my friends had the same problem with the exact sympoms that you have described, the fault was the Turbo, the waste gate was seized wide open, the problem was getting a new turbo at a reasonable cost as the mercrusier price was over £1000 ! trying the well known turbo suppliers brought down the price unfortunatley they were on back order last year with a 6 month wait so they had them repaired at a cost of around £400 they came back as new and work a treat.
regards
Calum

Can't the wastegate be replaced as opposed to the turbo? Surely if the wastegate was seized OPEN then there would be no turbo damage?

Just a thought