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Old 08-09-2015, 01:25 AM   #1
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Perkins or something else?

I am in the begining stages of putting a new boat together and looking for advice on power. The hull is 42 feet and full displacement. The best I can tell I will need 85 hp to reach hull speed. I have severial used Perkins already. One is a 6.354 NA that will need to be rebuilt. The other is a 6.354M turbo-aftercooled. The T/A seems to be in very good shape but it is missing the heat exchanger bundle from the multi cooler. I should have said the boat will be keel cooled and dry stack.
Thanks, David
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Old 08-09-2015, 03:07 AM   #2
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I used to have several Perkins motors parked in my shed in various states of broken and robbed for parts.
It finally dawned on me that the reason I had all these motors was that the one actually in the boat was in constant need of attention, and was taking a great deal of time and money to keep shipshape.
Since replacing it with the Cummins B, I have done a lot more fishing, and a lot less stressing about the engine.
Funny story about finally getting rid of the Perkinses, sold the entire lot to a youngster who was very excited about it all, and had his dad give me cash with a promise to show up the very next weekend with a truck to haul it all away.
Eighteen months later, not a whisper from the kid or his dad, no contact info, WTF???
So I put it on craigslist and sold it again, this time for a ridiculously low price, to a guy that was incredibly picky, wanted me to start the good motor up so he could hear it run, when he was getting 4 parts motors and a runner for $400!
This post is getting lengthy, but I think you might get the point by now...
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Old 08-09-2015, 07:43 AM   #3
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Keel cooled and dry stack ,

I would purchase a International DT 360 or 466 from a new wreck.

The engine in the lower 48 would run $3,000 or so, almost new.

A Twin Disc and custom exhaust manifold insulation wrap, and your in business.

Similar life as a DD series 50 or 60 with out the big price.
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Old 08-09-2015, 11:26 AM   #4
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Quote:
Originally Posted by DNT99611 View Post
I am in the begining stages of putting a new boat together and looking for advice on power. The hull is 42 feet and full displacement. The best I can tell I will need 85 hp to reach hull speed. I have severial used Perkins already. One is a 6.354 NA that will need to be rebuilt. The other is a 6.354M turbo-aftercooled. The T/A seems to be in very good shape but it is missing the heat exchanger bundle from the multi cooler. I should have said the boat will be keel cooled and dry stack.
Thanks, David
I have twin 1976, 6-354's, 130 hp NA, which being 39 years old now have performed flawlessly and have never been rebuilt. Injector pump and injectors are all original as well. The only weak point in the NA engine is the wet exhaust system which is no longer available from Perkins and are custom built by MESA Marine for around $1700 each. Since you're going dry stack you won't have to deal with the exhaust issue.

As in most diesels, what kills Perkins engines are poor maintenance practices and abuse.

You need 85 hp, the NA Perkins would be more than adequate for your needs and you would avoid the additional complication and noise of running a turbo'd engine. Best choice IMHO is rebuild the Perkins NA.
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Old 08-09-2015, 11:43 AM   #5
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The first question should be how much power do I need? The brand of engine is almost immaterial.

Knowing what I know I'd say you need an engine rated at about 80hp. So what engines are availible in the 70 to 90hp range?

And knowing your displacement would help you and this thread.
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Old 08-09-2015, 01:30 PM   #6
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Thanks to all for the replys.
In answer to displacement the best I can tell it will take about 44,000 to get it down on its water line.
The calulations say it will take 85 HP to get to hull speed. I have always heard it is best to have some reserve, up to 50%, for wind and waves? So what modern engine would work best for a trawler in this HP class? I am looking for one that is fully supported anyplace in the US. Simpler is better IMHO.
David
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Old 08-09-2015, 01:48 PM   #7
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John Deere engines are very popular in the troll fleet here.
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Old 08-09-2015, 03:12 PM   #8
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The Deere 80hp would clearly be an excellent choice at 4hp per ton power loading. That's what I have and I use 50% of it cruising. If your hull is more easily driven than most (more like a sailboat) then 65 to 70hp will do. And if you've got a huge rudder, bilge keels and an extra large keel 120hp or so would be better.

As to hull speed it's my opinion thart's no need to be able to achieve it. Many incorrectly think FD boats run at HS. Not so. You will never run at hull speed except (and maybe not there either) when you're checking props or your engine's health. You will probably find yourself running 1/2 to 1 knot below hull speed ... probably much closer to one knot below. I run at 6.15 knots w a HS of 7.

There is a huge difference in price between high end engines and other less common industrial engine conversions. If economy is important a used take out may work but the engine may have been abused. FF's favorite IH is another low buck engine that's probably very good. Probably way too much power for you. The 4cyl Cummins is good but many say it vibrates a lot. Same w the 4cyl Lehman. An old 4cyl (4-236) Perkins is good by many reports on this forum. When I get home I can give you a source for excellent marineized Izusu and Mitsubishi engines. Happy hunting.
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Old 08-09-2015, 03:59 PM   #9
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For long life on a NA at modest engine speeds ,

it takes about 3 cubic inches of engine displacement to create 1 HP.

75 HP cont?

a 225 to 250 cubic inch diesel engine would work.
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