2002 Diesel NO REVS WHEN INITIALLY ENGAGING DRIVE

"Hi I have a 22ft tug running

"Hi I have a 22ft tug running a twin cyclinder Volvo penta 2002 workboat setup. Please see my attempt at a

website ( under construction so contact links don't work at the moment ) and check the first page for pic of the engine and trans.

http://plan9.flemingc.on.ca/~damicamp/index.html The engine runs perfect and cold starts are not an issue

( good charge in batteries ). The engine runs cleanly up to around 2900rpm and idles fine. Recently I have

been having an issue with the transmission - or at least I think its the trans. Scenario..... If I start

the boat from cold the engine will fire and run as normal with full revs at hand in neutral. I let the

engine warm to normal temp. If I then engage drive - forward or reverse - it will not rev. If I apply full

throttle in either direction it will sit without the revs increasing. Now at this point I should say that

there is no obstruction to the prop as I can turn the drive shaft very easily by hand, and when I engage

either gear it does so perfectly and the shaft will rotate. So, there it will sit just wanting to rev but

not going anywhere. Now after about five mins or so attempting to get some forward or reverse motion the

revs will gradually creap up when in gear and then you will have full throttle in whichever direction you

were attempting to use. So I then move the shifter to the opposite direction expecting to have full

throttle but no, you will have to wait until the revs increase in that gear also ( maybe another 5 mins ).

But once you have got motion for the first time in either direction it will be on tap straight away ANY

time after that, its like it takes mins to get revs the first time but after that no problem for as long as

you are running. A few months ago when I put the boat in the water I had full throttle on demand straight

off the trailer with a cold engine. When you have drive it will work all day as if there are no problems,

and is 100 % reliable. This problem seems to be getting worse and only happens after the boat has been

unused for maybe 24 hrs or less? Any help or guidence would be greatly appreciated.
Thanks.
Damian."

"My guess You have an air-leak

"My guess You have an air-leak somewhere in the fuel line system.
As a test, suggest You take a canister/out-board tank and fill it with diesel. Attach it to the engine as close as possible, with a return back to the tank/canister.
Test.
Does return disappear or keeps on flowing?
Is it still a problem?"

"Hi I figured out what the iss

"Hi I figured out what the issue was. It turns out that once the engine is running and I engage forward or reverse, if I turn my battery switch to select just one of the two batteries and not both, the revs pick up perfectly. Until the batteries have received a full charge to replenish current used during starting, the engine is having trouble over coming the strain placed on it by the alternator. Alternator/battery/really low hp diesel that can't charge it's own batteries issue? lol. Thanks for your help."