Repowering old steel trawler

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Gardner Marine Diesel Engines for sale and new products releases - Express Diesel Service Ltd

I you are considering a rebuilt Gardner then perhaps consider a brand new doosan. Same "class" of engine. If there is no limit to your budget, then a dream engine would be a guascor

The way all this money is being slung around, w/o one hell of a deal that 671 looks better by the minute. $20k. Likely difference of repair of 671 vs quality 4stroke replacement will buy a lot of diesel. 671 burns this much - new 4stroke burn= ? $20? even $5k would be hard to justify.
The 4 stroke will be quiter though.

I second the 6CTA. My boat is 52' and 23 tons, I run my M1 engine (250 hp) at 1400 rpm and she does 7.5 knots. My fuel burn is 12 to 15 litres per hour using my Onan genset (7.5). You can get this engine in any config. up to about 485 hp.
Mine is dry stacked and keel cooled.

I would consider the availability of support along your intended cruising route for whatever engine you choose as a big factor in your choice.
Hopefully, the engine will run like a top and never skip a beat for years to come, but IF old Murphy shows up along the way, you will want parts and service in a timely manner.
In my years of dealing with trucks, boats, and heavy equipment, I think Cummins is the most proliferous brand out there, so parts and service will be the most readily available.
The 6B or C at moderate hp ratings are about the most bulletproof motors for the buck you will find.
As mentioned above, your most intelligent choice might made by running the boat for a while with the old DD to gather info/insight/data.
The 9.7 knots may be an unrealistic target for your cruise speed, unless the hull in question is very sleek indeed!

If dependability and parts availability are priorities the 6-71 at 170 hp should work just fine, parts and mechanics who can diagnose and repair are pretty easy to find almost anywhere. I would recommend that you use the boat for a years or so before making a decision on re-powering.

..more information to add... seaboard marine specialist recommendation is a Cummins recon 6CTA, 8,3 litters "all mechanic" rated at 320 hp at transmission.. no price but I suspect could be around 40k??
Gardner.. I used to have one in another commercial boat.. sturdy, reliable.. but in that case, my detroit looks much better with an overhaul...

makobuilders said:

Garrobito, the numbers you've given above don't jibe. But instead of trying to calculate power, just do like ski mentioned and measure your power at various speeds. From that you can extrapolate how much is needed for V/L 1.34, if you really think it's necessary to reach that speed.

BTW, you are exempt from having to install a T-3 engine as long as you trade-in to the dealer (don't sell the DD engine on your own unless you can prove transfer - check this with the dealer first). A good ole mechanical T-1 will get almost 10% better fuel economy. And absolutely stay away from glow plug engines. That Yanmar is the wrong solution.

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This is a great suggestion! I was ready to sell this old detroit... definitely I gonna explore a trade in first.. thanks you!!

River Cruiser said:

If dependability and parts availability are priorities the 6-71 at 170 hp should work just fine, parts and mechanics who can diagnose and repair are pretty easy to find almost anywhere. I would recommend that you use the boat for a years or so before making a decision on re-powering.

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..Problem I want to go north with that trawler... I don't know if I can trust an old engine while I'm 70/100 miles off coast with my family... re powering is gonna add a safety key to our trip...
Second point is Detroit is awful expensive on diesel.. new engine is gonna give me at least 10% less consumption (depend conditions off course )

garrobito said:

..Problem I want to go north with that trawler... I don't know if I can trust an old engine while I'm 70/100 miles off coast with my family... re powering is gonna add a safety key to our trip...
Second point is Detroit is awful expensive on diesel.. new engine is gonna give me at least 10% less consumption (depend conditions off course )

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So you are going to spend $40K to save 10% on fuel consumption??? This doesn't pass the smell test. Just overhaul the engine you got and you will be a happy camper.

garrobito said:

..my detroit looks much better with an overhaul...

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By keeping the same engine you avoid all the changes accommodating and fitting a different one, from mounts to instrumentation and everything in between.

Overhaul my detroit is a good business if I do for myself.. I become lazy with the years... a re manufactured one cost me 17K plus all the time and hassle to remove old one, send it for core replacement and reinstall new one..
I'm going for a Cummins Recon 6CTA for 25K without tranny... I prefer install new one, difference on technology and quality is good for the equation investment/prestation.

I would be running the 6-71 for at least a while. The payback on all the "Fuel Savings" would be years away and probably not under your ownership if you consider the repower cost. 6-71's are loud, dirty and not so fuel miserly. If its run at 1400 RPMS it is not so noisey, not so loud and very fuel efffcient. Detroit engine longevity is legendary.

Sailor of Fortune said:

I would be running the 6-71 for at least a while. The payback on all the "Fuel Savings" would be years away and probably not under your ownership if you consider the repower cost. 6-71's are loud, dirty and not so fuel miserly. If its run at 1400 RPMS it is not so noisey, not so loud and very fuel efffcient. Detroit engine longevity is legendary.

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and you an buy parts all over the world