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Old 03-23-2019, 08:41 AM   #81
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When it comes to burn rate vs speed, they are the manufacturer's and builder's numbers and may not relate to YOUR reality.
When you get the boat loaded with your stuff, make your own fuel curve noting sea state, apparent wind direction and speed plus other information you feel important.
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Old 03-24-2019, 06:03 AM   #82
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If you repower a boat with something different than OEM, than you should do it for yourself and not care about resale. I believe most prospective buyers will walk away quickly, when they see what has been done.
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Old 03-24-2019, 06:39 AM   #83
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Not sure if the OP is still following this thread. If so, what did he decide to do?

BTW that boat only displaces about 8 tons. He really doesn't need much more than 40hp if he is cruising at 7 knots or less. But with all that top hamper he'll likely have to add some ballast down low.
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Old 03-24-2019, 11:25 AM   #84
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I have repowered boats with odd engines and it can be done very economically if you're willing to get your hands dirty a little.

For example, I repowered a 40' trawler with a 120 hp turbocharged Isuzu to replace a Lehman-Ford 6 cylinder. What that involves, though is putting a non-marine spec (i.e. non water cooled exhaust turbine) engine in, and you and your insurance company will have to be cool with that. This repower completely transformed that old boat - the Isuzu is so smooth and quiet, it seems like an electric motor is propelling the boat, plus the Isuzu never leaks a drop of anything and starts instantly.

I have made water injection elbows using threaded stainless fittings, and welding in sea water injection pipes. I've done this with the Isuzu, a Perkins 6-354 Turbo and a 33 Hp Yanmar.

The part that requires the most engineering is making a mount for the sea water pump. I use a fanbelt drive sea water pump - Jabsco makes some - and take some time to get the bracket really rigid and the alignment of the drive pulley right.

The heat exchanger can be easily mounted to the hull and only needs radiator hoses to connect to the engine. You should buy an expansion tank with radiator cap (Summit Racing has some, also Jeg's).

Mounting the transmission is not all that hard - just be sure you get an engine with an SAE standard bellhousing and flywheel. You'll need to get a bellhousing adaptor to mount the gear to the housing - Hurth/ZF have the necessary adaptors.

Good Luck!
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Old 03-24-2019, 11:31 AM   #85
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Emergencies

Didn’t finish: I spent 8 k which is about 15% of what the whole boat is worth. Did I give it more value for resale? I don’t think so. Find the right boat !! When I think of it ... cushions 2 k. Fridge 1.5 , heater 3 k, electric toilet , new top 6 k, electronics with radar 5 k, this is just scratching the surface. To go to a smaller engine and gamble with my safety after all this??? And I did Most of it other than cushions myself. Buy the best equipped vessel you can find
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Old 03-24-2019, 12:41 PM   #86
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Originally Posted by gfr51 View Post
Well being a backyard mechanic I called around the block and a guy with supposedly 38 years experience with cat diesels, in my instance, said that basically you are just removing all of the turbo and afterburner stuff and plugging some holes left by the removal. I am sure you would have to re-tune the injector pump. As for resale you still will have all of the factory parts to put back on. Yes you may want to get a different prop for low end torque.
I am planning on travelling around on this boat not sitting so I can appreciate 1/2 half gallon or more per hour!
In researching online I came to the conclusion that they are taking a standard non turbo engine and pumping it up to way more horsepower causing longevity issues.
I also called Caterpillar Technical Line and they said Oh No we don't recommend changing the factory motors because they are specially built with stronger pistons, connecting rods, cylinder heads to accept the extreme pressures.... Me being an old time Drag Racer I am thinking Oh Boy I would have a much stronger....more well built motor....with suddenly much less strain put to it....In my thinking that makes for a much longer lasting rig.
Correct me if I am wrong.
regards, Gary
Having owned and run more diesels than any sane man should be allowed, one must grasp the principles of the design. If you have ever had a td that lost its boost, you end up with a slug, not an economical n/a oil burner. I am a huge advocate of a well designed diesel and the best overall economy to smiles ratio has come from an intercooled turbo diesel.
You asked for educated opinions on your swap and now a detuning, many old salts have shared their wisdom and experience with you, it doesn't get better than that.
My advice, buy something you are happy with and use it, trust me, you'll find plenty of things to work on in your new to you 20+ year old boat...
Like my dentist in Managua once explained to me "I can probably make a pair of shoes and they may be ok but I'd rather have the shoemaker make a pair and know they are correct" he's not a maxillofacial surgeon but a very good dentist.
Trust the marine architects and engineers that designed the boat, buy what you want as it was designed, rube goldbergs are generally a disaster. Sail is another option and you can get some incredible economy with that propulsion design. Good luck.
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Old 03-24-2019, 12:44 PM   #87
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I don't know the water conditions in your area, in my area currents can be a significant issue. I want a larger engine so it isn't as stressed at the possible top speed of the boat. But I also want extra Oomph when more power would get me out of a stressful situation.

In the video below, the first half shows a boat successfully and without much stress making it through a rapid current condition in Dodd Narrows in British Columbia. But jump to the 1:05 minute mark, and you might question the sanity of the skipper of that boat. What these mental midgets don't realize is that an engine is designed to handle so much stress, then it over heats, or has the possibility of over heating.

I have a retired Captain from the BC Ferries assist me in decisions with my boat refit and when I was discussing a larger engine (actually the engine is smaller than the old Merc engine but cranks out an additional 110 hp), he said the extra hp would be of benefit in "iffy" currents. He then related a story of one of the larger BC ferries being caught by a swift current and swung 360 degrees before control of the ship could be re-established.

Beginning at the 1:05 mark, you can see the skipper has no margin of error safety in his motor, its going full tilt and we can safely assume being stressed by forces it wasn't designed for:

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Old 03-24-2019, 10:41 PM   #88
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Originally Posted by rsn48 View Post
I don't know the water conditions in your area, in my area currents can be a significant issue. I want a larger engine so it isn't as stressed at the possible top speed of the boat. But I also want extra Oomph when more power would get me out of a stressful situation.

In the video below, the first half shows a boat successfully and without much stress making it through a rapid current condition in Dodd Narrows in British Columbia. But jump to the 1:05 minute mark, and you might question the sanity of the skipper of that boat. What these mental midgets don't realize is that an engine is designed to handle so much stress, then it over heats, or has the possibility of over heating.

I have a retired Captain from the BC Ferries assist me in decisions with my boat refit and when I was discussing a larger engine (actually the engine is smaller than the old Merc engine but cranks out an additional 110 hp), he said the extra hp would be of benefit in "iffy" currents. He then related a story of one of the larger BC ferries being caught by a swift current and swung 360 degrees before control of the ship could be re-established.

Beginning at the 1:05 mark, you can see the skipper has no margin of error safety in his motor, its going full tilt and we can safely assume being stressed by forces it wasn't designed for:


Although you may perceive the person at 1:05 as a mental midget I see it as one of the ways to get through Dodd before all the morons try it at slack water. I once transited as your "midget" did against a full run. I have a 65' single, full displacement hull. Ran the back eddy as far as I could and dove out into the current. Crawled through at full rpm with the Graymarine Detroit screaming.
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Old 04-20-2020, 11:36 PM   #89
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See the attached data sheet for the Cummins B210

I've attached a copy of the data sheet for my Cummins B210. Specifically, it is a 6BT5.9-M. Based on the data sheet, I think my RPM, HP, and fuel burn numbers are correct. I know the RPM and fuel burn numbers are correct, because I have a tachometer and a fuel flow meter. I don't have any reason not to believe the HP numbers from the Cummins data sheet.
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File Type: pdf Cummins B210 Performance Data Sheet.pdf (99.9 KB, 15 views)
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Old 04-21-2020, 06:51 AM   #90
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Your mistake is reading the hp #'s off the full load table and reading the fuel burn off the prop load table.
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Old 04-21-2020, 08:49 AM   #91
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Don't do it. The others have hit on most of the reasons, here is one more raindrop for your parade.

When I removed the engine from my 36 foot Albin. (A F.L. 120 which probably weighs close to a thousand pounds) It really made little to no difference in the waterline. Maybe an inch, maybe even two inches, no more than that.

I have two 150 gallon water tanks at the very stern of the boat, right up against the transom. Even with that location and the weight of 300 gallons of water (well over a ton, twice the weight of the engine) The difference between full and empty is just a couple inches.

You will not reduce your draft enough to make a difference by exchanging a little engine for a bigger one.

While I am raining on your parade I might as well add. Converting an old tractor engine to marine use is best left up to the experts.

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