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Old 22-02-2015, 23:22   #31
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Re: perkins 4.108 over heat on high rpm

Please tell us the max rpm obtainable in freerunning fwd gear.
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Old 23-02-2015, 08:18   #32
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Re: perkins 4.108 over heat on high rpm

I cruise @ 2100-2200 and can rev to 3000, however, I have been told I should never go over 2700 rpm. I generally cruise @ 6-6.7 knts. I have a 24" max prop which is great.
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Old 23-02-2015, 08:46   #33
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Re: perkins 4.108 over heat on high rpm

I fought the heating issues on mine for a while ... pulled the bundle of tubes in the exchanger, and had a raditor shop clean it out..
and the temp would still climb over 200 when I reved it up over 1800 for any period of time...
So I went back and read the shop manual... now isnt that something, the manual says the opperationg temp should run between 180 and 220....
And just to make sure all was right, I installed a manual guage , still kept the electronic unit... the manual guage would read 190 while the electronic would read 200..
as the prop being "over proped" The manual on our motor stated max as 3600 on the "NEW" 56 hp motor.. Maxie Prop says to set the prop to "CHOKE" the motor with the prop about 200 less than max RPM.. We did and our Max RPM while in gear is 3400.. We uasally opperate around 1800 to 2000 for best power, fuel usage, and smoothness...
With our tempeture at about 190 to 210 depending
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Old 23-02-2015, 17:27   #34
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Re: perkins 4.108 over heat on high rpm

Have you cleaned the exhaust injection elbow? Again...
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Old 26-02-2015, 18:00   #35
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Re: perkins 4.108 over heat on high rpm

I had the overheating problem and went through cleaning the heat exchanger etc. I then hit on the engine heated hot water tank that was original equipment, I bypassed the hot water tank and the engine now runs at an acceptable temperature at all RPMs. The water flow through the coils slow down and allows for deposits to collect.
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Old 26-02-2015, 18:08   #36
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Re: perkins 4.108 over heat on high rpm

..too much salt on the circuit?? time to flush with salt-rite??
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Old 26-02-2015, 20:02   #37
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Re: perkins 4.108 over heat on high rpm

I had been battling with the overheating problem on my 4108 over 2500rpm for over 10 years.
the problem on my heat exchanger was that the brass tubes had been vibrating inside on the cast aluminium body of the heat exchanger, grinding the internal hole where the brass bundle of tubes go through. because this hole was bigger,(should be a tight fit) allowing the cooling water to bypass the tubes, instead of being forced trough the tubes to cool the water. Replacing the heat exchanger fixed my problem.
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Old 26-02-2015, 23:19   #38
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Re: perkins 4.108 over heat on high rpm

Quote:
Originally Posted by Seman View Post
I had been battling with the overheating problem on my 4108 over 2500rpm for over 10 years.
the problem on my heat exchanger was that the brass tubes had been vibrating inside on the cast aluminium body of the heat exchanger, grinding the internal hole where the brass bundle of tubes go through. because this hole was bigger,(should be a tight fit) allowing the cooling water to bypass the tubes, instead of being forced trough the tubes to cool the water. Replacing the heat exchanger fixed my problem.
One of the better diagnoses. He had the engine on a test "stand" with no boat stuff hooked up and it overheated.

It has to be internal to the engine. Internal leakage of the exhanger is a good guess.
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