Volvo MD 22L will not accelerate anymore

[edventure]

I do have 2 Volvo Penta MD 22L engines in my sailboat. They both do have same problem:
The engines do start without any problem. I can run them for hours without any problem but if I would bring back the throttle to neutral and than do try to accelerate again (backwards or forwards) the transmission (PRM Delta) is engaging (the shaft is turning slowly) but the motor is not reacting but remains running stationair(quite regular though) as if the throttle would still be in neutral position.
This problem starts to occur only after 2 hours of running; if I let the engine rest a while/cool down (having it neutral is already sufficient) the engine would engage again as normal (but after a limited period of time the same problem will occur). Strangely enough, if the problem occurs and I dis-engage the transmission the motor will accelerate without any delay.
The engines are 2 stand-alone machines that have their own filters, tubing etc) except for the diesel tank (approx. 700 liter). Filters have been renewed; tubing have been blown through.
Any ideas on what could cause this problem are very welcome

K.R.
Eddy

[Wotname]

I can't help you with your engine problem but I have responded so that you will see this thread again in your new post tab. Reference to your other thread http://www.cruisersforum.com/forums/...st-201345.html

[Sailmonkey]

Have you tried disconnecting the throttle linkage (Morse cable) from the engine when this occurs, then place the gear selector in gear and increasing the throttle on the engine?

Your problem sounds more like a bad engine control rather than a bad engine

[edventure]

Many thanks. I will give it a try.
But do you have thoughts that it occurs to both engines at same time and only after that the engines has run for approx. 2 hours or more.

[Sailmonkey]

Originally Posted by edventure

Many thanks. I will give it a try.
But do you have thoughts that it occurs to both engines at same time and only after that the engines has run for approx. 2 hours or more.

Ahhh, sorry for some reason I read one engine.

Do both engines pull from the same fuel tank? If yes, is the vent clear for the tank?

[edventure]

I am not sure if the vent is open but it is a 700 li tank which not more than 50% full at max. Could a blocked vent with such a large tank still cause this issue?
I do know that at a certain point in time I have run the engines with an open tank top (but I do not recall if this was when the problems occurred). I will give it an other try.

[TreblePlink]

Gotta be a blocked tank vent which eventually sets up a vacuum, or debris intermittently blocking the fuel pickup.

[Sailmonkey]

Originally Posted by edventure

I am not sure if the vent is open but it is a 700 li tank which not more than 50% full at max. Could a blocked vent with such a large tank still cause this issue?
I do know that at a certain point in time I have run the engines with an open tank top (but I do not recall if this was when the problems occurred). I will give it an other try.

Of course it can. The larger the tank is the longer it takes to create a vacuum, but air is still needed to replace the fuel that has been consumed

[sailormed]

Easy to check: next time you use engine leave filler cap off. If problem is over, cause is ventline, otherwise continu investigating the other possibilities.