Perkins 4108 power problem

[FiandDog]

Our Perkins 4108 has plenty of revs in neutral but only about half max revs in gear. We've spent 5 days having it checked by "professionals" who have done the following - checked exhaust right through, air filter, changed fuel filters, checked water trap, tested all injectors, done compression tests, checked tappet settings and apart from suggesting a new fuel pump may be the answer the problem remains. If anyone can assist/advise we would be extremely gratefull otherwise our 2-year cruise may reduce to under 1!

Many thanks, Fi and Dog

[pfatyol]

Also check the propeller. Make sure it is not covered with growth.

Good luck

[FiandDog]

Thank you so much for that, we really appreciate your assistance - unfortunately I should have mentioned we checked the prop for fouling and movement first!

[sailingdog]

What kind of prop do you have on the boat? Is it the right size? Was this engine ever able to get up to max revs in gear before, or is this a new to you boat and you don't know. If it was previously able to do so, and is no longer able to do so, that's a very different case than if you don't know.

[Indawindz]

Fi
You never state what they found. ie compression good or bad valves adjusted propperly etc. I would check my fuel lines real good, it sounds like you might be sucking air into the fuel.

[OneManNoDucks]

Fi

My engine (Perkins M92B - 86 hp) had exactly the same symptoms as you've described - Fine in neutral, only half max revs in gear. I have a Maxprop 3-blade variable pitch propellor. The solution for me in the end was to adjust the pitch on the propellor blades.

Hope that helps. Cheers.

[FiandDog]

Thank you again for replies. Prop is not new so we know as it's clean and free running and all worked well before that this is not the problem. All testing on injectors etc were okay and nothing untorward found, exhaust clear etc etc. Fuel lines checked and tried running engine from separate tank and problem still exists.

[FiandDog]

Hi again - that's interesting.........we have a 3-blade variable pitch maxi-prop we've been running with for 6 years with no probs - was yours a problem when the prop was new or did it just develop over time?

[CarolinaB]

Hi,
This happened on our boat a couple of months back, but I don't remember whether it was just in forward gear or not.

What had happened was the throttle connection to the fuel pump had come out of adjustment. I don't know the exact details but the Cap'n adjusted the cable at the pump and after that we were able to rev up the engine.

[FiandDog]

Hi CarolinaB and thanks for your advice. I've confirmed with the engineer and he's checked the throttle connection so unfortunately we have to rule that out also. The only thing left is a new fuel pump - being connected as we speak - so we have our fingers crossed (as desparate folk do!).

Many thanks for trying to help, F