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Old 06-27-2012, 03:16 PM   #21
skipperdude's Avatar
City: Whittier AK
Country: USA
Vessel Name: Apache II
Vessel Model: 1974 Donald Jones
Join Date: Oct 2007
Posts: 3,147
Most diesel experts suggest running at WOT every 4 to 6 hours of continues operation.
5 or 10 minutes should do the trick.
Or so I have been told.


If you can't repair it maybe it shouldn't be on the boat
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Old 06-27-2012, 04:29 PM   #22
Scraping Paint
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
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Originally Posted by ben2go View Post
Diesels are speed/rpm governed through the injection pump.So they are very hard to over rev..
Give yours a snoot full of lube oil and let us know what happens.

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Old 06-27-2012, 07:42 PM   #23
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City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
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120 Lehmans should run 2500rpm at WOT in gear.
Anything else is under propping or over propping.
One usually uses pitch, diameter and trimming blade area to achieve rated rpm in gear.
I recently mounted a new prop and am down 100rpm. So I'm 100 rpm over propped. The boat has less power, runs to fast at idle and the engine seems to not run as freely as it did before.
I think American Marine is telling people what they think they want to hear. 2250rpm is well over propped and telling people to "cruise" at 1800 is excluding many very important variables. From all I've heard about AM I think one should seek advice elsewhere. Boat is a good place to look but of course there will be opinions there too. I've said for some time here to seek technical advice from engineers and manufacturers and seek service from mechanics.
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Old 06-28-2012, 05:46 AM   #24
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"If need be, they can change both for better performance on your boat."

In every case "BETTER " will need to be defined.

Higher top speed?

More bollard pull?

Lower fuel burn at cruise?

Longer engine life?

Lower noise level?

Less shaft noise and vibration?

Are all beginning consideration for the eventual compromise..
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Old 06-29-2012, 01:11 PM   #25
City: hilton head
Country: usa
Join Date: Jun 2012
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As I said....The info here is great!
Optical tach??? Will research..
Exhaust clear..but is long on a 36 GB,,
Dia-Pitch vs rpm great info..
I am burning 2.85GPH at 1950 GPS sez 8-8.3 KTS still water. Very happy with that.
Will ck prop size on next haul in fall. Till then happy-just trying to sqeeze a little more ground speed.. As an old (very) F8Crusader driver it;s hard to get used to the difference in speed!Ha Ha...
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Old 06-29-2012, 11:45 PM   #26
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City: Gig Harbor
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Harbor Freight for the optical tach. Until you have calibrated your tachs you are just guessing.

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