Can't reach peak rpms

[RogerandJoanne]

My boat is a 28' Albin with a 315 Yanmar. Boat runs fine, however, can't seem to go over 2900 rpms. Changed filters, had the bottom checked, checked fuel pick-up, checked prop. Recently took the boat up the Hudson, where, at one point, it felt like the boat "shifted gears" and it went up to 3300 rpms. Ran fine the rest of the week; next time we used it, boat would not go over 2900 rpms again. Seems to be not getting enough fuel but everything is checking out fine. Any advice would be appreciated. Thanks, Roger Dunn

[Serenity]

You might want to have your engine photo tached to determine if your tach is accurate. When my boat was repowered the tach was off considerably. I installed a new tach from Aetna and problem was solved. Does your speed increase/ decrease at various rpm's.? You should be able to hit 3900 +, perhaps you are over propped.

[jcollins]

When the boat had the "shifted gears" condition happen, did you hear the engine speed up? If yes, could it be fuel filters? If not, I agree with Max.

[RogerandJoanne]

All was fine until a recent trip; the boat felt like it was dragging at first, cleared up, was okay for the rest of the trip and then it started dragging again and hasn't cleared up. The tach does seem to be fine, the engine won't go over 15-17 knots with or against current and the tach maxes out at 2900 rpms, so it seems as though it's not getting enough fuel because when it did clear up, it took off and went up to 36-3700 rpms. Made me think that there was a blockage that cleared itself up, but then blocked again. My mechanic thought possibly the high pressure pump? Thank you for your suggestions - it's frustrating. Appreciate them both. Roger

[DougSea]

Any smoke? Different vibrations?

[RobS]

If not a fuel restriction, have him check the turbo, do you here it spinning up? Run with the engine box open and take the foam filter off the air cage, you'll hear it if she is spinning. Has the after cooler ever been serviced? Turbo wash is cheap and easy, give that a try.

[RogerandJoanne]

Hi Guys, thanks so much for your help; it's not smoking; my mechanic did check the turbo - it's spinning freely and did a turbo wash. Fuel restriction is a possibility - where could that be if not the high pressure pump? I really appreciate any and all advice. Rog

[N4QC]

Fuel for thought –

Fuel filters have been mentioned. Make sure that the fuel filter gaskets, on both the primary and secondary filter housings are seated correctly as you may be sucking air at a particular fuel rate.

Fuel lines: make sure that you don’t have a collapsing fuel line.

Adequate air: Try running with the engine hatch open. See if there is a change in engine operation when opening and closing the hatch. Also, look for fuel wet spots around the injectors, oil residue around the valve cover and breather connections after running with the hatch open. A turbo will act as a vacuum cleaner and these wet spots are sucked up by the turbo when there is restricted air in the engine compartment.

Fuel tank: Possible crud in the tank blocking the pick up tube. Possible vacuum problem with the tank system - is the vent working correctly?

Hope this helps,

[DougSea]

Joe - excellent troubleshooting list.

Rog - Hope it turns out to be a simple issue!