|
| Author |
Message |
    
Stephen Thurley
New member
Username: sthurley
Post Number: 1
Registered: 05-2009
| | Posted on Sunday, May 10, 2009 - 05:16 pm: | 
|
Hello - I am new to this site tonight - so here goes:
I have a Volvo penta MD5a in my 1980 Pegasus 800 sailing yacht. The engine was overhauled in 2005 with new valves, reseated etc. I bought the boat in 2008. Over the winter the engine started to loose power/revs about 5mins after start up. I figured it to be the cold etc but I have recently changed the fuel filters and tightened all connections. The problem has not gone away. The engine currnetly starts fine but very, very slow to pick up revs. When I put it in gear the engine just sits at tick over speed - this has caught me out twice now after casting off ropes!! If I let the engine run for 5 to 10 minutes, it seems to sort itself out and will then run fine for hours (recently came back from a cruise after running the engine about 3 hours, naturally though on start up it did as explained above) Some freinds have also pointed out that the top end revs dont seem enough - even though the engine pushes me along at 4.5 to 5.2 knots - depending on conditions (when the drive is disengaged the revs go crazy - with drive engaged they reach about half of this) Another person has suggested that she may be overpropped - it has a two blade fixed prop now, the folding one must have been repalced. I have yet to change the oil and filters - oil currently very black looking. Has anyone any suggestions (the fuel is fresh by the way, and I have just replaced the exhaust elbow - not a cheap exercise) |
Richard Vosbury
Member
Username: vosman
Post Number: 46
Registered: 01-2009
| | Posted on Monday, May 11, 2009 - 08:51 am: |
|
Sounds like it is overloaded from fouling. Or prop is to large. Also check that alternator is not overcharging. |
Gordon Pawelchak
Member
Username: alchemist
Post Number: 5
Registered: 12-2006
| | Posted on Sunday, July 12, 2009 - 02:04 am: |
|
A while ago I had my MD5B rebuilt and had a great deal of grief along the way. It turned out that my problem was a damaged governor. When the engine is assembled or disassemble the governor can come into contact with the injector linkage if the linkage isn’t hooked to the injector. The levers tend to flop around and can conflict with the governor and damage it if governor is rotated slightly. The governor is very simple but very fragile. My mechanic went through a couple governors before he discovered the conflict. It is very subtle!
With the damaged governor, my engine ran okay a high throttle but wouldn’t idle worth a darn. This was after the rebuild and on subsequent disassembly we found the broken governor. The damage was to the hardened steel pins that hold the springs. These pins are very hard and brittle.
If you pull off the cover over the governor, check to see that weights and springs function as expected. |
|
|
