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Old 29-05-2016, 11:18   #1
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Perkins dies at low RPM

Perkins dies in low rpm.
It seems to run ok when she was cold. After she rungets warm and you put her in neutral, she just dies. This means you can not stop by putting her in reverse, since she dies when you get from forward to neutral position.

This boat is not mine yet, but I did make a downpaiment. So if someone could give me advise about it, I would sure appreciate it. I like to think that it is only a fuel problem and the engine might be ok. But I am really not a mecanic at all. Thanks in advance
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Old 29-05-2016, 11:20   #2
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Re: Perkins dies at low RPM

Check the idle set screw. Bump it up.
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Old 29-05-2016, 11:24   #3
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Re: Perkins dies at low RPM

Which Perkins?
They made quite a few engines..
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Old 29-05-2016, 11:27   #4
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Re: Perkins dies at low RPM

5 will get you 10, it's the high pressure fuel pump. Next it will get hard to start when engine is hot.
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Old 29-05-2016, 11:32   #5
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Re: Perkins dies at low RPM

You should be able to adjust the idle fuel supply with a set screw or cable to tighten.
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Old 29-05-2016, 11:46   #6
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Re: Perkins dies at low RPM

Can't separate the two suggestions without knowing what RPM you mean by "low" or "idle." Check the manual for the specified idle RPM. If the engine is running under load at that RPM and shifting to neutral without shifting the throttle stops it, you've got a problem that goes beyond the idle speed set screw. But if you have a single lever control (one arm controls both throttle and gearshift, a combination I don't like) then when you shift to neutral you may also be dropping the throttle below idle speed, and need to adjust the idle, as suggested. Let's all hope that's the problem.
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Old 29-05-2016, 11:54   #7
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Re: Perkins dies at low RPM

there should be a lever on injector pump for kill pull.... make sure that is with a cable.
then idle it up. read your engine manual to make sure you get it right.
or call a mechanic.
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Old 29-05-2016, 18:18   #8
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Re: Perkins dies at low RPM

A diesel is controlled by a governor, so at idle, under a load or not. the rpm should remain constant. The governor on engines with a injector pump is inside the pump. The speed control lever usually on a side and sometimes connected to kill linkage, usually has two adjustment screws. One screw sets idle and the other max rpm. Your idle is set too low. But there could be other issues. Usually the screws are set and never touched between pump overhauls.
Since you're in the process of buying the boat, an engine surveyor might be worth the cost.
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Old 30-05-2016, 00:32   #9
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Re: Perkins dies at low RPM

Thank you all. The owner will have a mecanic look at this issue. Btw it seems to be a 4801 with 49.32 hp. I will try to convince the owner to have a full service done. This would give me some peace of mind, since the boat is in really good shape otherwise and I would like to buy it. Tks again.
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Old 30-05-2016, 08:15   #10
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Perkins dying

I believe you meant to say 4-108 Perkins. Anyway, it is a very reliable workhorse. I advise getting a report from the mechanic just so you know and understand what was done to correct the problem. Then, if it reappears you will have something in writing to refer to.

good luck with your "new" boat!
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Old 30-05-2016, 09:02   #11
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Re: Perkins dies at low RPM

Recommend changing out the primary and secondary fuel filters before attacking any other engine idle adjustments. As well, determine fuel vents are clear. Sounds like it is having difficulty sucking fuel at low revs.
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Old 30-05-2016, 09:04   #12
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Re: Perkins dying

Quote:
Originally Posted by wunderluster View Post
I believe you meant to say 4-108 Perkins. Anyway, it is a very reliable workhorse. I advise getting a report from the mechanic just so you know and understand what was done to correct the problem. Then, if it reappears you will have something in writing to refer to.

good luck with your "new" boat!
Yup, time to call in the pros. If one thing is wrong, a lot of things are probably about to go wrong. Sounds like a compression issue. If you can rev it up without load but not with load, might have a cracked head, cracked head gasket, etc. Or could be your compression releases are not closed.
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Old 30-05-2016, 09:21   #13
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Re: Perkins dies at low RPM

There are no compression releases on a 4-108. The heads, head gaskets and head bolts are greatly beefed up on this engine as opposed the 4-107. If it's dying in neutral it's not a load issue. 99% of issues with all diesels dying at low revs is either fuel or air starvation. Besides fuel restriction look for air obstruction.
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Old 30-05-2016, 11:36   #14
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Re: Perkins dies at low RPM

As above, look at fuel or air supply problems. Easiest to diagnose is air, just take the filter off. If it runs better you know where the problem is. Don't run it permanently that way, just the few minutes it takes to diagnose.
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Old 30-05-2016, 13:22   #15
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Re: Perkins dies at low RPM

agree with changing fuel filters first, and then note the RPM. if low as per the manual then make a idle adjustment if needed
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