Luxury on a miser budget

The only major difference in the 6.2/6.5 diesel and the 454 is the exhaust manifolds, starter and flywheel. The 454 flywheel will bolt up but she will shake like dog passin a peach seed, not the same balance. Also, if the 454s were older they are probably counter rotating and have either velvet drive or paragon gears. neither will work with the non counter rotating diesels. The hurth 630 or 800 is a good gear for this swap, but it is a down angle gear so motor mounts would need massaged a bit. Twin disc 502s would also work. I dont know of a straight in swap for either the VD or the paragon. The vd is a straight thru and the Paragon is a drop center gear. Possibly the later model borg warner gears would work, but I'm not familiar with them. In any case, one gear needs to be able to reverse the rotation of the shaft. I used the 630s in my conversion.

Forgot about fuel issues. You would need a return line, thats about it. Complete engines can be had from a salvage yard for less than $500. I like the 1993 model engines or previous, mechanical injector pumps and serpentine belts, high flow water pumps. $3000 for a COMPLETE rebuild, flywheels at $150 each, new starters at $200 (estimate, probably way cheaper or just have existing ones rebuilt) Exhaust manifolds are expensive, probably around $3000 total, unless you can find a used set. So close to 12k with all new stuff. I dont think it would ever pay out on fuel savings the way most boats are used but if buying a boat with clapped 454s it is a viable option.

kulas44 said:

What gears. Mine has the Allison MH20's. Not really compatible with the 6bt's as far as I can tell. If they were I could just change to a 3-1 ratio.

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I think some have the TwinDisc MG1500V, some others have a ZF but don't know model #.

This is a great thread!

It seems to me that it could only make financial sense if the engines to be replaced have serious mechanical issues. As in both clapped out and maybe one of them inop.

I think if you are going to much lighter engines like going from a 6V92 or 8V92 to the Cummins it will be important to consider vertical center of gravity. I would actually spend some money to talk to a N.A. even for coastal cruising. Maybe one of the fancy "design a boat" computer programs would give you enough information if you are better on a computer than I am....... In any event it should take less weight in lead or batteries as you should be able to get the weight lower than the center of mass of the engines.

In this case it really doesnt matter. I cannot afford to lose any weight. The weight that will be lost is as low as possible, I need to keep the "added" weight as low or lower. Stability is not an issue. The only question is " how to add the weight"?

>Adding a lead keel ???. Your thoughts are appreciated.<

It is far easier creating an inch of trim by moving weights than creating an inch of immersion with pig lead.

Anything you can do to move or remove weight from the bow area?

500ft of 1/2 chain? Big bow water tank? 1500lb dink on chocks?

I have a washer/dryer unit and the old dryer up front. The boat originally had a washer and a dryer, the washing machine was junk and I removed it. I had a splendide unit in my shop so just installed it. They are fairly heavy and I had planned on getting a new stand alone washer so that will remove some weight, but not enough to make much difference. I agree that weight removal would be a much better approach. There just isnt much up there to lose. No chain, yet, but will be eventually. No dinghy on the bow, yet. The biggest problem is that these boats were designed for a cruising couple and as such have relatively large fuel and water tankage, (1000 fuel, 500 water) which is great, except when tanks are low. Its a sportfisher so has a lot of stern boyancy, not much bow boyancy, great for busting big waves and a smooth ride in the rough. The design cause it to be stern high at rest when the tanks are not full.

... if you want a new 6.5 or 6.6 GM diesel, contact these guys...I seem to recall that the company was originally based in Stillwater Oklahoma some ten years ago and then moved to Sweden.

Marinediesel AB*|*Supercharged V8 diesel engines – A Force Of Nature

Al you have a very good idea except for the fact that most of the boats that you'd pick for the project are planing or SD types. Not suited for full disp speeds.

I saw a GB 36 that had 55hp Yanmars a few years ago and it didn't stay long on the market. But to do a good job you'd need to modify the hull aft to make it into a FD craft. One would do best at that holding hands w a NA but it shouldn't take much money. It would take considerable time and effort cutting out the stern and glassing in the new shape. SawsAll anybody?

By the way if you had the choice of a Perkins 107 or 108 I'd pick the 108 as it doesn't have O ring seals on the wet liners to leak when the engine gets old. One of the reasons I re powered Willy.

But your idea has real merit for real cheap trawler if the running at disp speeds inefficiently w a faster hull is acceptable. The SD or planing hulls will have at least 1.5 times as much drag and some SD hulls will double the drag over a FD type. Planing hulls could have 3times as much. Many on this forum in their wishful thinking think it's not so and my opinion is just that .. an opinion.

The project I'm looking at, is a 50' planing hull. I don't expect to get "trawler" type efficiency, but by down-powering it will become much more efficient and much more reliable than original.
Right now it's getting about 1 1/2 GPM, and the old 6v92's could hand grenade at any minute. If I repower, accepting the loss in speed, I think I can go to 2 MPG at intracoastal speed, and 1 1/2 MPG at about 12knts, and will still be able to get 18-20 knots max. I can live with that. The Cummins 6BT's at 200-250 HP are ultra-reliable.
I also accept that it's not an offshore hull, but I can have a 50' widebody, shallowdraft, very comfortable liveaboard, intracoastal cruiser. Right now the boat can get from Ft Lauderdale to Daytona on a tank, with some work I think I can go Ft Lauderdale to Virginia Bch on the same tank, another tank will get me up to my families place in Maine. Shallow draft will let me do the canals around Montreal/Ottawa/Erie and the lakes etc.

BerettaRacer said:

... another tank will get me up to my families place in Maine...

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Where in Maine... per chance Camden, Rockport, Rockland region?

Grew up there, some family in Portland area, some inland.

I have studied the fuel usage extensively on my planing hull boat. If I run one engine at 7 knots I can get 2 mpg. Thats just above idle. Lots of 48 foot fd boats do about that. I "think" if I replace the DDs with 6b cummins I could get to 3 mpg on one engine at 7 knots. As good as about any fd boat of the same size. At these speeds in protected water hull shape makes little difference in mpg.

I totally understand the differences that hull shape can make. I also own a 50 foot James Krogen designed trawler. The pre cursor to the Krogen 42. Mine was built in 1972. What I dont see is the massively better fuel economy that most people think happens with single engine fd hulls. Evidence does not support it. A 50 foot boat getting 3 mpg at 7 mph is about average if using enough power to get it to that speed. Assuming diesel of course. What we run into is that most boats are so far overpowered for running slow that if we run both engines we are not close to be loaded enough for any kind of efficiency. Newer electronically controlled engines are much better at this. If we are looking for that last 1/2 mpg them maybe a pair of 75 hp yanmars in a 50 foot boat would get it. I would be more comfortable with a pair of cummins 4b's or two perkins 4-236"s. preference would be the perkins at 85 hp each. non turbo and simple. Physics dictates that it takes x amount of power to move x amount of resistance thru the water at x speed. Less speed means drag is reduced exponentially, almost to the point that square is an exceptable hull form if speed is low enough. River barges for example.

Another thing to consider are the parasitic losses inherent with larger engines. Bigger gears and shaft bearings make a difference. The amount of power absorbed just to run the engine itself can be fairly high. For example, a 1970 ford 375 hp 429 cubic inch engine required 50 hp just to run it to make the rated 375 hp. I'm sure a 8v92 or 6v92 would have substantial pumping losses at any speed. It seems like the key is finding that balance between small enough to do the job and big enough to make the operator comfortable. Its not a direct correlation between parasitic loss and rated power because, again, as speed is reduced (rpm) drag (engine friction) is reduced even more. So the difference to produce 7 knots with a big engine running slow is not that much different than doing the same job with a smaller engine running faster. If we could just pour diesel in the water and set it on fire to make the boat move it would be more efficient, no pumping or parasitic losses. If you wanted to go faster you could just get a bigger bucket.

Kulas 44,
You need to stop thinking about 400hp and hull speed.
If you're going to live in the world of displacement boating you should be running (w your WLL) we'll over one knot BELOW hull speed.
Or you're going to need your 400hp.
A 25ton FD hull would need about 100hp total and use about 60hp to run 1.25knots under hull speed.
But you're running a planing hull so you may need something closer to those 400hp engines after all.
And 100hp applied to the shaft should require about 5gph. But I think you'll need a bit more power so maybe 7 gph.
Does that compute on your end?

Al ... The Tanacious. Are you going to purchase the Tenacious and repower? Marin and I talked about the Tenacious and came to the conclusion that there was no connection to GB. I thought perhaps she was a burned GB 36 w a new cabin built on the old hull.
Interesting that she only has 60hp. In my book that would be to her credit.

Actually the boat in question, my sportfisher, has abut 1200 hp. I would require about 120 to make hull speed of 9 knots, and a lot less for 7.5 The big motors are very ineficient at those speeds, but they do run great at 27 knots, at about 60 to 70 gph. I dont do that to often. I just think it would be a much better boat with smaller engines, used for cruising at low speed. The next fellow would probably want to go with some Cummins m11s at around 650 hp each. To each his own. I like slow.

Kulas44,
You're in good company here then and a belated "Welcome Aboard!"

Thanks, been a lurker here for awhile, used to spend a lot of time over on the "other" trawler forum, great bunch of folks. Also like a couple of fishing/boat forums and the old standby WoodenBoatForum. I really like the discussions here, especially this one. If I come off a little "know-it-ally" I apologize. I'm probably like the old boy that has never driven or rode in anything but a 1974 pinto. He would tell you that you cannot pass uphill, end of story. My experiences are not vast enough to support my opinions, but I dont mind being called out either. I hope to meet everyone here on the water someday.

kulas44 said:

Thanks, been a lurker here for awhile, used to spend a lot of time over on the "other" trawler forum, great bunch of folks. Also like a couple of fishing/boat forums and the old standby WoodenBoatForum. I really like the discussions here, especially this one. If I come off a little "know-it-ally" I apologize. I'm probably like the old boy that has never driven or rode in anything but a 1974 pinto. He would tell you that you cannot pass uphill, end of story. My experiences are not vast enough to support my opinions, but I dont mind being called out either. I hope to meet everyone here on the water someday.

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Hi Kulas44

You should feel right at home here, welcome aboard. It appears we in TF are pretty much comprised of a bunch of boys with our own feelings of correctness from learned experience/knowledge... and of course some well placed Admiral input. Sometimes we’re correct in how we feel and what we say – sometimes we simply are not! Don't usually find too many in their 20's or even 30's that like the diverse types of pleasure craft represented here, maybe a few though!

Although I've been hanging onto 38 yrs as my age for well over two decades, might have to up it into the 40’s... looken in da mirror just don’t hold me anywhere near the 30’s at all now (40’s either for that matter!). Tiz kind of a joke around here about my age... cause as Jonathan Winters would sort of kiddingly say... “My body’s about but my mind bailed out!” - LOL

Pict is bout 5 yrs ago... Happy Boating Daze! - Art

I'm 29, cause 30 is old. In my mind anyway. My wife however is still 21 when I look at her. Only problems is we've been married about 35 years. I'm not good with math.

Eric, You may have seen this photo of the "Tenacious" but Marin may not. It gives a better perspective of the hull in relation to the "Spray" the American Marine Ltd. craft.
While the Tenacious is NOT a Grand Banks it is the hull form that Kenneth Smith perfected prior to American Marine contracting him to design the 36. Just saying.
Al

Spray photo again following.
http://www.grandbanks.com/images/editorialreviews/passagemaker_fall1998_gbhistory.pdf