volvo md5a 110s saildrive no power

[sthurley]

Can anyone relate to this:

I have a pegasus 800 with an md5a and 110s saildrive - the yacht is 1980 and the engine original it received new vlaves etc and a rebuild of sorts in 2006. I bought the boat in 2008 and the engine ran fine until January. It starts brilliantly but after 2-3 mins the revs would drop away then lift then drop then finally settle normal again. I figured this was due to air and fuel filters - all replaced now and connections tightened - still happens. When I put her full forwards or backwards the revs stay at idle speed. after 5mins or so everthing jumps into life. At full bore the yacht reaches 5knts bottom is clean prop is clean etc. It sounds like fuel issues and has been described to me that the governor at the injection pump may be gummed up and only once warm clears itself. Does anybody have any thoughts before I start taking bits apart?

 

[Simes]

Sounds like a govenor issue. I do not like takeing them apart. Really a specialist job.

You might try one of the fuel treatments, Fuel Set, Marine 16 Fuel Maintenance ect. These are all supposed to help keep the fuel system clean.

It is possible that the Injector pump / govenor is worn and only when warm do the tolerences close sufficiently for it to deliver the correct amount of fuel.
Sorry for no new thaoughts

Simes

 

[Cliveshep]

I don't know anything about your particular enginer but FWIW on my Thorneycroft similar behaviour turned out to be air trapped in the injector pump which was cleared by repeated and forceful bleeding eventually. Mind you, the slightest leak in any of the pipework is what allows this air to get sucked in in the forst place.