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Old 12-10-2015, 07:18 PM   #1
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1985 Perkins Range 4 motor

I don't want to hijack the other Perkins thread, but did have a question or so about the Perkins Range 4 motors (200 HP).
Instead of dealing with the dreaded manicooler (when it fails) would it be possible to simply remove the turbo and install a standard Perkins exhaust and make it a normally aspirated system?
I have no knowledge of the difference in compression or camshaft specs between the 2 motors, but this would seem to be the real issue in doing this modification, other than standard Perkins exhaust parts being able to bolt on.
I don't hot rod the boat, but do let it run hard for 15 to 20 minutes each time out. Normal cruise speed is 11 knots at 1200 rpm, 15 knots max now.
Any ideas?
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Old 12-10-2015, 08:15 PM   #2
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Hmmm! I suspect you meant that normal cruise speed is 11 knots at 2,200 rpm, not 1,200 rpm.


Turbo charged engines usually have lower compression ratio than normally aspirated engines- different pistons usually. Check the part numbers for the two to know for sure.


Also I doubt that you can get up to 11 kts with no turbo, maybe at wot but you don't want to cruise that way.


And finally how does this save your manicooler. You need cooling for other things still with no turbo, right? You would have to replace its function with expensive parts from a NA engine.


I must admit I am slightly ignorant of what a manicooler does. I assume that it is a single casting and tube bundle that cools the air after the turbo, includes a main heat exchanger and also is integrated with the exhaust manifold to keep it cool.


David
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Old 12-11-2015, 07:16 AM   #3
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Quote:
And finally how does this save your manicooler. You need cooling for other things still with no turbo, right? You would have to replace its function with expensive parts from a NA engine.


I must admit I am slightly ignorant of what a manicooler does. I assume that it is a single casting and tube bundle that cools the air after the turbo, includes a main heat exchanger and also is integrated with the exhaust manifold to keep it cool.
You are correct David.
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Old 12-11-2015, 12:25 PM   #4
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Orca makes a replacement Manicooler and also most of the parts necessary to go back to the seperate manifolds arrangement. I see Manicoolers on ebay very often. Not to worry, there are so many Perkins out there, there will always be parts OEM or otherwise.
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Old 12-11-2015, 03:50 PM   #5
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I have no current problems, but sometimes I just stop and wonder about "when" they fail. I will take a look at ORCA again, as perhaps I missed it when I looked.
Thank you!
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