RPM limitation when in gear Perkins 4108

[Paul M]

Hi all:
I have a Morgan OI 41 with a Perkins 4108. I recently got stuck on a sandbar and had to rev my engine beyond the 2200rpm I usually stick to. Since then, my engine will not rev beyond 2000rpm when in gear, forward or reverse. When in neutral, it revs as high as I want it to go. I don’t see any breaks in the accelerator cable linkage etc. Any ideas on what would cause this?

Thanks in advance,

Paul

[Cheechako]

Do you know for a fact that it ever went above 2200? maybe that's where it's propped? or maybe sand washed into the cutlass and it's torn up..? Transmission issues?

[Paul M]

Yeah, it used to run over 3000 but we always kept it around 2000 to keep the temp down. These engines seem to heat up quickly even at 2500rpm.

[_andi_]

Any colored fumes from the exhaust? If not I'd say not enough diesel. Check filters, plumbing, injectors.

[Paul M]

Good point! I am on the lower 1/4 of a tank of fuel. I guess due to decreased torque, these issues wouldn’t necessarily affect rpm in neutral. Is that correct?

[a64pilot]

Can you turn the shaft by hand in neutral?

[_andi_]

Originally Posted by Paul M

Good point! I am on the lower 1/4 of a tank of fuel. I guess due to decreased torque, these issues wouldn’t necessarily affect rpm in neutral. Is that correct?

Yeah, basically. You don't need that much energy (fuel) to rev just the engine without any load.

Then really check all filters, sieves, tank, ..., loss of performance is usually the first sign of blockage/accumulated sludge.

[danielamartindm]

Have you checked visually to see if anything is fouling the prop?

[DougR]

Does the throttle linkage on the injection pump actually move to full throttle position when you move the throttle lever to full throttle?

If so, then start looking for fuel restrictions, or the outside chance that something loosened up and is restricting the exhaust flow.

DougR

[Redpcx]

Also check for intake air restriction.
If an air filter has been added, remove it temporarily.
Of course, if you have a flame arrestor, make sure you put it back after testing.

[ZULU40]

my first thought was, dirty injectors

[Greg Mason]

My 4.108 had a problem like that, and it was my Max prop over propped. At top end, the stern just dug in but n more speed, and the engine ran hot. After changing pitch, the revs went up and the boat stayed level in the water. Just a thought.

[hamburking]

If you ran aground, you may have dislodged some sludge in the tank. Check your filters. A clogged filter would limit the fuel. Also, if you revved high that one time, it may have sucked with more suckiness than usual, sucking some sludge into the filter. Well, its easy enough to check the filter, right? Maybe even change the filter just to eliminate the easy fix. You may want to check your water intake strainer as well.

[hamburking]

Any chance you damaged your prop, strut, or cutlass bearing? Time to get one of the underwater cameras on a stick to check it out. Do they sell an underwater drone yet?

[Cadence]

Originally Posted by Paul M

Hi all:
I have a Morgan OI 41 with a Perkins 4108. I recently got stuck on a sandbar and had to rev my engine beyond the 2200rpm I usually stick to. Since then, my engine will not rev beyond 2000rpm when in gear, forward or reverse. When in neutral, it revs as high as I want it to go. I don’t see any breaks in the accelerator cable linkage etc. Any ideas on what would cause this?

Thanks in advance,

Paul

Paul,
I would guess the grounding bent you wheel.