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Old 01-01-2024, 14:40   #1
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Perkins 4.108 help PLEASE!!!

I have a Gulf Star 39 Sailmaster with a Perkins 4.108 diesel engine. Up until the weather turned cold it never has given us any problems. Since it's been cold out, and after sitting without running for about a month, we were ready to leave. She started a little rough but idled great for about 30-45 minutes. I pulled anchor and went to turn into the channel, I throttled up to what should have been 2500 RPM and couldn't get there Max throttle would only yield 1800-2000 rpm. It died and I was able to re anchor and found a loose fuel line and fixed it and she fired up again. So we tried again. Still cannot throttle above 2000 in gear. In neutral it revs fine up to 3-4k. I do notice more white steam like smoke coming out of the exhaust and it's leaving an oil shean in the water. I don't have any water mixing with my oil, and my coolant reservoir is free if any oil, but could my head gasket have blown? Any thoughts?
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Old 01-01-2024, 15:13   #2
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Re: Perkins 4.108 help PLEASE!!!

First thought - fouled prop.
Second thought - fouled bottom
Third thought - fouled prop and bottom.
Fourth thought - diesel supply problem (filter/air/tank vent blocked etc)

Look at the above in order before thinking head gasket.
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Old 01-01-2024, 15:20   #3
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Re: Perkins 4.108 help PLEASE!!!

I agree with Wotname--fouled prop and bottom. I once helped a friend move his boat in South Carolina. We left the dock with the current pushing us backwards and the engine couldn't generate enough power to move us forward due to the prop being completely foul.
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Old 01-01-2024, 15:22   #4
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Re: Perkins 4.108 help PLEASE!!!

Thank you for responding. I had a diver come out and check my prop, he said there was a little but not enough to foul, the fuel filter is new. I found a leaky fuel inlet line on the fuel pump and buttoned it up. She starts great and purrs like a kitten, but blows a lot of white steam like smoke and is leaving a pretty good sheen on the water still.
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Old 01-01-2024, 15:40   #5
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Re: Perkins 4.108 help PLEASE!!!

OK, presumably the diver removed whatever little prop fouling there was so that is eliminated; for future reference it doesn't take much fouling on the blade area to load up a prop.

Another cause - lack of air as in a restricted exhaust system (mixing elbow etc).

The white steam is also symptom of a hot exhaust - again a mixing elbow restriction or a decrease in raw water pump output. Impeller etc or a restriction in raw water seacock/strainer/hose.
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Old 01-01-2024, 15:45   #6
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Re: Perkins 4.108 help PLEASE!!!

Do you have a normal exhaust water flow? How’s the water temp on the closed system? Is it running warmer than normal? May be worth checking the exhaust elbow. If the inlet is plugged, you’ll have a noticeable reduction in water from the exhaust and it will run hot. I can’t imagine your indication of oil slick. That would indicate an incomplete burn but if the exhaust is white, that would not compute. Check the simplest stuff first. Is it still not reaching WOT?
If it’s running you’ve ruled out air. Don’t be confused about rpm without load. If the engine is not under load with the governor working, doesn’t mean much.
Good luck Ken
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Old 01-01-2024, 16:01   #7
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Re: Perkins 4.108 help PLEASE!!!

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Originally Posted by Kazamaran View Post
..... If the inlet is plugged, you’ll have a noticeable reduction in water from the exhaust and it will run hot. I can’t imagine your indication of oil slick. .....
All good points Ken.
Sometimes an exhaust that gets hotter than normal will release built up diesel/oil/carbon fouling that has accumulated inside the exhaust hose over a long period of time with the engine running under low loads.

Also note a severely restricted exhaust (i.e. high back pressure) can restrict air inlet flow due to poor cylinder scavenging. E.G. say a 70 or 80 percent exhaust restriction will not affect air intake much but if the restriction rises to say 90+ percent in the exhaust side and throttle is opened right up, the back pressure limits the amount of clean air that can be inducted into the cylinder. The resulting burn is incomplete (too rich) further restricting the exhaust.
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Old 01-01-2024, 22:41   #8
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Re: Perkins 4.108 help PLEASE!!!

Plus one for all the previous comments, they’re exactly the things to check first. Is there anything different about your engine installation that might pull the rpm down, propshaft brake or alternator ? refrigeration compressor? High output alternator or dual alternators? Smart regulator? Any of these can pull down the rpm, although if you’re getting 3-4,000 rpm high idle I suspect its not front pulley load causing the problem. Can you turn the propshaft easily by hand ? Do you have a fixed, folding or feathering propeller.
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Old 06-02-2024, 12:55   #9
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Re: Perkins 4.108 help PLEASE!!!

@Wotname suggested list of things to check seems the correct order. Any news on how it evolved? I just had my freshwater pump changed today on my 4.236.
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Old 06-02-2024, 19:48   #10
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Re: Perkins 4.108 help PLEASE!!!

Quote:
Originally Posted by SVPodunk View Post
I have a Gulf Star 39 Sailmaster with a Perkins 4.108 diesel engine. Up until the weather turned cold it never has given us any problems. Since it's been cold out, and after sitting without running for about a month, we were ready to leave. She started a little rough but idled great for about 30-45 minutes. I pulled anchor and went to turn into the channel, I throttled up to what should have been 2500 RPM and couldn't get there Max throttle would only yield 1800-2000 rpm. It died and I was able to re anchor and found a loose fuel line and fixed it and she fired up again. So we tried again. Still cannot throttle above 2000 in gear. In neutral it revs fine up to 3-4k. I do notice more white steam like smoke coming out of the exhaust and it's leaving an oil shean in the water. I don't have any water mixing with my oil, and my coolant reservoir is free if any oil, but could my head gasket have blown? Any thoughts?
Head gasket ?
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Old 06-02-2024, 20:55   #11
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Re: Perkins 4.108 help PLEASE!!!

Do you have an air cleaner on the engine,is it clear and clean ,how old is the fuel,have you added any fuel conditioner,is the air verry cold ,has the exhaust elbow been checked and cleaned recently,.one test or some call it a trick,remove the air cleaner ond using a heat gun gently blow hot air into the inlet if the helps start checking the above,4/108 are verry hard to kill,⛵️⚓️
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