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Old 14-11-2020, 16:04   #1
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Perkins 4.108 - Rebuild or ???

Thanks to this forum, I found a lightly used Perkins 4.180 engine off of a Kohler generator, and I'm in the process of getting this engine ready to replace the heavily used, smoking, leaking and overheating 4.108 on my Morgan 33' OI Pilothouse.

I've pulled the generator parts off of the engine, and am considering the following:

Replace rear main seal with Foley upgraded version.
Clean fuel injection system.
Replace gaskets
Paint the engine

My question to the group is, should I do a complete rebuild, or just what I'm planning to do here?

Should I consider doing any other upgrades, such as listed on https://www.foleyengines.com/perkins...4-108-update/? Anything else I should make sure to do while I have the engine out of the boat?

Attached are some pictures of the engine as it stands.

Thanks in advance!
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Old 14-11-2020, 16:07   #2
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Re: Perkins 4.108 - Rebuild or ???

I would, at a minimum, since itís easy now.
Change the front and rear seals, and clean/paint the engine.

The rest can be done once itís in and proven to run well.
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Old 14-11-2020, 16:10   #3
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Re: Perkins 4.108 - Rebuild or ???

Everything depends on the state it is in. Take off the head and you will know what your decision is for sure. My guess is a complete rebuild, I said guess.
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Old 14-11-2020, 16:20   #4
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Re: Perkins 4.108 - Rebuild or ???

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Originally Posted by sailormed View Post
Everything depends on the state it is in. Take off the head and you will know what your decision is for sure. My guess is a complete rebuild, I said guess.
I agree about removing the head I think, you can find out how much cylinder ridge there is. Generators run full out rpm 100% of the time. Does it have the right governor for a power engine?
Strangely my '85 4-108 leaked zero oil.
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Old 14-11-2020, 16:21   #5
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Re: Perkins 4.108 - Rebuild or ???

I seem to recall early episodes from Sailing Uma where they wanted to install a new-to-them engine they had scavenged from a generator. They had issues adapting the governor that ran the engine at a consistent 1800 RPM, so much of an issue that they abandoned the attempt and went withe their first install of an electric motor.

I forget exactly, and while I'm a decent garage mechanic, this is a bit beyond me. Any thoughts on taking a motor from a generator that runs at a consistent rpm and adapting for propulsion?

Peter
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Old 14-11-2020, 16:54   #6
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Re: Perkins 4.108 - Rebuild or ???

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Originally Posted by mvweebles View Post
I

I forget exactly, and while I'm a decent garage mechanic, this is a bit beyond me. Any thoughts on taking a motor from a generator that runs at a consistent rpm and adapting for propulsion?

Peter


A lot depends on the engine.

Engines like an 05 series Kubota may or maybe not have different injectors optimized for a specified rpm range, but typically use the same governor as a propulsion engine. If I wanted to I could adjust the stops on our throttle position arm and create a constant speed engine.
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Old 14-11-2020, 17:33   #7
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Re: Perkins 4.108 - Rebuild or ???

Do you know how many hours are on this engine? Have you checked the compression? Just replacing the crankshaft seals won't solve oil leaks if the blow-by pressure is too high. And, as already said, generator engines are run flat out for long periods of time. If the rings need replacing you are going to bore or replace the cylinder sleeves so at that point you may as well do the full rebuild.

When I was faced with the rebuild or replace decision with my 4-108 17 years ago I choose to replace. The rebuild cost may not be a viable solution, especially if you need a major part like an injection pump or a crankshaft.
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Old 14-11-2020, 17:33   #8
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Re: Perkins 4.108 - Rebuild or ???

I'd run a leak down and compression test. If both pass, I'd reseal it, change all coolant hoses.
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Old 14-11-2020, 17:44   #9
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Re: Perkins 4.108 - Rebuild or ???

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Originally Posted by Cruiser2B View Post
I'd run a leak down and compression test. If both pass, I'd reseal it, change all coolant hoses.

what he said,
+ Set tappet clearances since you have rocker cover off.
Clean hx if it has one.
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Old 14-11-2020, 19:48   #10
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Re: Perkins 4.108 - Rebuild or ???

Quote:
Originally Posted by Cheechako View Post
I agree about removing the head I think, you can find out how much cylinder ridge there is. Generators run full out rpm 100% of the time. Does it have the right governor for a power engine?
Strangely my '85 4-108 leaked zero oil.
I have wondered the same thing. The fuel governors look the same, but I have no idea. I can always swap out from my existing engine or at least thatís what Iíve been telling myself. 😂
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Old 14-11-2020, 20:01   #11
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Re: Perkins 4.108 - Rebuild or ???

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Originally Posted by btompkins View Post
I have wondered the same thing. The fuel governors look the same, but I have no idea. I can always swap out from my existing engine or at least thatís what Iíve been telling myself. 😂
Providing that they are the same engine, treat the new one as a long block and transfer all the peripherals over.
I would ensure that the new one is a good runner before doing too much to it though.
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Old 14-11-2020, 21:16   #12
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Re: Perkins 4.108 - Rebuild or ???

It's an easy engine to rebuild and it's out of the boat now.
Coming from generator service, the injector pump is probably optimized for 1800 rpm.
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Old 15-11-2020, 08:23   #13
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Re: Perkins 4.108 - Rebuild or ???

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Originally Posted by Lepke View Post
It's an easy engine to rebuild and it's out of the boat now.
Coming from generator service, the injector pump is probably optimized for 1800 rpm.
Yes, it looks like it's held open with a spring. I'll take some pictures, as this seems to be the main issue for now. Thanks!
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Old 15-11-2020, 08:24   #14
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Re: Perkins 4.108 - Rebuild or ???

Quote:
Originally Posted by Lepke View Post
It's an easy engine to rebuild and it's out of the boat now.
Coming from generator service, the injector pump is probably optimized for 1800 rpm.
It doesn't look hard, and I agree. Two things concern me, the special tools needed, and cutting the valve seats looks a little intimidating. Is it really that easy?
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Old 15-11-2020, 08:27   #15
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Re: Perkins 4.108 - Rebuild or ???

Quote:
Originally Posted by Uncle Bob View Post
Providing that they are the same engine, treat the new one as a long block and transfer all the peripherals over.
I would ensure that the new one is a good runner before doing too much to it though.
I think it is a good runner. I do plan on moving some over, the transmission and bell housing, flywheel etc. It has the newer model heat exchanger, which is good I think, but the one thing that has me scratching my head is that it has a belt driven water pump">raw water pump. I like this better than the other option, but it seems like it will require a fourth pulley, which I'm not sure how to get setup. I was looking at the serpentine systems, but don't need a huge alternator as far as I know, but maybe I should JIK? Still wondering about the fourth pully. Probably could just use the engine driven raw pump if I have to.
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