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Old 19-05-2019, 23:49   #1
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Perkins no power under load

Hey Guys, I'm back with my troublesome Perkins Prima M80T turbo....

Setup: After running 8 hours under full load no problems, I was coming into an anchorage and throttled down to half or so. Then to idle forward, looking for a spot. When I tried to add throttle then, the revs would not rise much above idle. I had forward power, but only idle forward to a bit more than that if I pushed the remote forward. Same in reverse, idle astern to a bit more if I goosed it. From idle 1000 rpm to about 12-1300 max.

Symptoms: Engine starts immediately, repeatedly, runs at idle fine. In neutral it revs high as I want as usual, 3000+. Checked throttle linkage, moving the body all the way (as is obvious in neutral). Checked propeller but no obstruction. High pressure fuel pump was just repaired/checked out by a pro shop and reinstalled FYI.

Strange note may be important: Motoring last time I felt the RPMs drop for a second, I pulled back to idle, pushed it forward again and it ran fine. Thought i snagged a line or the throttle remote slipped (it was recently greased). Ran fine for another 10 hours after that.

I'm hoping it's a classic filter clog, and about to change the racor filter and then the engine fuel filter if no improvement. Just looking for any other ideas because I'm here with one of my mother in laws on a tiny island and her vacation is dwindling rapidly if I'm stuck here

Any other thoughts that match these symptoms?
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Old 20-05-2019, 00:14   #2
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Re: Perkins no power under load

Looks like the engine and its controls are fine as you can run full revs in neutral.
And because you can get the engine only to rev to 12-1300 RPM when in gear, looks like the problem is in gearbox, propshaft, bearing or prop.
Check the engine room: is the shaft is clear of any debris?
Do you have a brake on the shaft? is that inadvertently activated?
Can you dive in the water (engine is turned off, gearbox in neutral and engine key is hidden, so no-one can start engine); then check if the prop has a rope around it? And if not, try to turn the prop either way. If it does, then the problem is likely in the gearbox.
If you can not turn the prop (shaft) easily......
Ooops, just realise you have an Amel SM, not even sure if you can turn prop on your kind of boat as you have a C or U drive, with the prop behind the keel.
Still, I would check the prop in the water.
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Old 20-05-2019, 00:16   #3
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Re: Perkins no power under load

Note: Engine temps spot on fine all day. Turbo replaced and new, but has been blowing smoke enough and pulling only 1/4 the amount it should that next week I was scheduled to have it pulled because mechanic thought it might have been a faulty new....any chance a blown turbo would produce these symptoms?
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Old 20-05-2019, 00:32   #4
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Re: Perkins no power under load

Best guess, fuel feed. You checked the filters and the mesh filter (if fitted) at the pump? If filters OK, could be intake in tank or hoses. Or fuel pump.

gearbox, prop are also possibilities, as well as an injector pump problem. Turbo, I doubt it, but yes, you would loose a lot of power.
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Old 20-05-2019, 02:31   #5
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Re: Perkins no power under load

Hi Sojourner
I have the same engine without turbo, your problem is most likley the transmission,(Hurth ?)
I faced the same situation last year, happens after motoring several hours.
The fix for me was to go to neutral, rev up the Engine and "throw" it into gear.
I had the transmission rebuild.
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Old 20-05-2019, 05:06   #6
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Re: Perkins no power under load

The fix for me was to go to neutral, rev up the Engine and "throw" it into gear.

Wow! If it wasn't the transmission before, it certainly was afterwards!
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Old 20-05-2019, 05:13   #7
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Re: Perkins no power under load

The turbo is easy enough to check.....pull the exhaust elbow off and have a look at the turbine wheel ( engine off of course). It should be easy to spin with your fingers and a light coat of carbon. If totally sooted up its a problem.....
The compressor wheel on the inlet side should be relatively clean as well....a light coat of oil on it won't hurt much. If the turbo was a problem you should have lots of black smoke under load....

A fuel restriction would give good running at low RPM, and inability to rev under load with no black smoke. Fuel filters, lift pump, fuel pickup pipe in the tank. Try running off of separate fuel tank.

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Old 20-05-2019, 05:15   #8
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Perkins no power under load

Symptoms of a blown turbo is low power of course because of not enough air, however you still get all of the fuel, so it smokes like a train, I mean scary amount of smoke, you can’t miss it.

If it were anything in the transmission pulling the motor down, then you would get lots of smoke as if you were seriously overpropped, and of course the transmission would be so hot it would likely smell hot and be hot to the touch, cause all that engine power is going into friction, which is a lot of heat of course. A boost gauge would tell for sure, but I bet your not hearing the slight whistle of the turbo are you?

Only thing comes to mind to me is fuel delivery, however they don’t usually do as your is, usually if really clogged, they bog down and shut down, but maybe with a new pump it’s strong enough to pull enough fuel for a smooth idle?

I’m under the impression that the Amel sail drive and transmission is pretty robust, but I have heard of one get water in it from the cooler.
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Old 20-05-2019, 05:24   #9
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Re: Perkins no power under load

Thanks for the replies guys... Tried running it cold this morning, same symptoms, changed the racor and engine fuel filters... Got power back but at the upper Rpm range it takes 10 seconds or so to come up above 2200 rpms to 2600 or so. Should be fine to get back to my mechanic who was gonna pull the turbo anyway cause as I said, it was pulling 0.5 at full throttle full load instead of 2 or something like that.... I'll update when it gets sorted... Thanks!
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Old 20-05-2019, 06:05   #10
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Re: Perkins no power under load

I would suspect that you only got part of your power back......
Whatever plugged your Racor and engine fuel filters is still restricting fuel flow and causing sluggish response and low turbo boost. Remember, no fuel, no boost.

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Old 20-05-2019, 06:09   #11
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Re: Perkins no power under load

Do you have an emergency fuel shutoff? Mine got inadvertently partially closed once with quite the same symptoms you describe.
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Old 20-05-2019, 06:13   #12
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Re: Perkins no power under load

The 2200 to 2600 can be turbo related. Sounds like the turbo is not spinning up quickly.
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Old 20-05-2019, 14:17   #13
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Re: Perkins no power under load

Crack in fuel pipe.
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Old 20-05-2019, 14:43   #14
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Re: Perkins no power under load

Plus 1 as in above. sucked some air.
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Old 20-05-2019, 15:47   #15
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Re: Perkins no power under load

My turbo Cat 3116 would lose power ar higher rpm due to air being sucked in at the Racor filter due to faulty seal on the pressure gauge mounted in place of the normal T handle. Hopefully not the transmission which is big $$$.
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