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Old 05-02-2017, 09:15 AM   #1
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Repowering MT 34. Is it worth it?

I have a 1979 Marine Trader Europa Sedan with a FL 120 in it. Runs great but I'm starting to find it a bit slow. Against the wind and current (St. Lawrence River) I will often drop around 4 knots. I'd like to have a bit more power to never go under 6 and to reach 8-9 with no opposing forces.

Would putting in a new engine get me the extra speed I'm looking for or is it just wishful thinking?

There is a guy in my marina who has a MT 36 and repowered with a Volvo 200 HP (I think) and he goes significantly faster than me.

(No need to get into the cost debate at this point, just the rationale new engine vs speed).
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Old 05-02-2017, 09:28 AM   #2
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Well, cost is always an issue.

A remanned Cummins 6BT 210 hp engine would give you that extra speed. So if that is all you are interested in, stop reading here.

But it will cost about $25,000 for the engine alone and maybe a new transmission, prop shaft and prop will also be required. Installation will be at least $10,000. So you are talking about a minimum of $35,000 and as much as $50,000.

Do you want to do that on a boat that may be worth less than that now and afterwards worth only a bit more?

David
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Old 05-02-2017, 09:57 AM   #3
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Even looking strictly at new engine vs speed, I can't see how it would make sense to repower. You have a good-running Ford Lehman and you're constrained by your theoretical hull speed, not more than 7 kits or so. Maybe take a look to see if your bottom is clean and remove some weight from the boat if possible. Both of these would give you a little more speed.
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Old 05-02-2017, 10:45 AM   #4
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Even looking strictly at new engine vs speed, I can't see how it would make sense to repower. You have a good-running Ford Lehman and you're constrained by your theoretical hull speed, not more than 7 kits or so. Maybe take a look to see if your bottom is clean and remove some weight from the boat if possible. Both of these would give you a little more speed.
He's only constrained if he doesn't have the hp to push past it.
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Old 05-02-2017, 10:47 AM   #5
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There is a guy in my marina who has a MT 36 and repowered with a Volvo 200 HP (I think) and he goes significantly faster than me.
You've answered your own question.
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Old 05-02-2017, 11:43 AM   #6
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Have you checked the obvious? Are you reaching the correct WOT RPM's, Dirty bottom, is your engine propped correctly. Maybe you have done all of this and just not made it clear? A 3 knot current on the nose is going to slow you down by 3 knots regardless of the size of the engine.
Hull speed for 34 feet is 7 knots. You needs lots of power / fuel / $$$$ to push it further. Not sure if 200 horses wil be enough to get it over the hump.
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Old 05-02-2017, 11:55 AM   #7
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There really isn't a hump on semi-displacement trawlers like the MT 34. The more hp you apply, the faster you go.

Theoretically the MT 34 should take 40-50 hp to go hull speed which is about 7 kts. I suspect that his current FL 120 is overpropped and probably can only put out less than 100 hp at wot. Even 100 hp should get him to 8-9 kts at wot. The Cummins 210 can be run at 150 hp all day long and that should push him to 10 kts.

But is it worth it?

David
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Old 05-02-2017, 12:06 PM   #8
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.... but I'm starting to find it a bit slow. .
What changed ? Has this always been your speed but now you're not as happy with it now, or did you used to have more speed and have slowed down ??
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Old 05-02-2017, 12:08 PM   #9
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There really isn't a hump on semi-displacement trawlers like the MT 34. The more hp you apply, the faster you go.

Theoretically the MT 34 should take 40-50 hp to go hull speed which is about 7 kts. I suspect that his current FL 120 is overpropped and probably can only put out less than 100 hp at wot. Even 100 hp should get him to 8-9 kts at wot. The Cummins 210 can be run at 150 hp all day long and that should push him to 10 kts.

But is it worth it?

David
Bigger boat might be a better investment.
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Old 05-02-2017, 02:42 PM   #10
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Nice thing is about half the time that current is on your tail!!! More than half if you are good at planning.
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Old 05-02-2017, 02:48 PM   #11
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Invest in tide and current tables.
I too love my old 34 MT but she ain't never gonna get a $50,000.00 engine upgrade.
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Old 05-02-2017, 02:58 PM   #12
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Greetings,
Mr. F. Short answer. No, IMO. Not worth the time, expense or possible aggravation. Sell what you have and put the $$+the refit $$ into a faster vessel.
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Old 05-02-2017, 03:02 PM   #13
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Invest in tide and current tables.
I too love my old 34 MT but she ain't never gonna get a $50,000.00 engine upgrade.


^^^This...^^^

Instead of repowering the trawler "my" choice would be to buy a jet powered center console Rhib.

Nothing at all against tossing money at boats you'll never see again I just think bang for the buck wise if you want speed buy a speedier boat. I recently sold an old school Toyota Land Cruiser because I was tired of VW Buses passing me on the freeway.

Maybe at least consider the possibility of selling the MT and get a nice older sport fish in the 38' range? Throttling back to ten knots they are surprisingly easy on fuel.
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Old 05-02-2017, 03:20 PM   #14
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no amount of HP is going to help you at the" narrows" against the current. I had a screen shot of a fairtide passage of our nav computer doing 18 plus knots in a tug.
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Old 05-02-2017, 07:59 PM   #15
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Swapping to cummins is cheap. And parts for them are dirt cheap compared to the lehman.

I am swapping a lehman 120 for a cummins 6b 120 hp (non turbo). Its fully rebuilt and has the heat exchanger, exhaust manifold, and velvet drive adapter for $5K.

A brand new cummins 6BT long block can be bought for ~$5K. Thats $5,000 not $25,000.

Throw in another 5G's to marinize it, and get the turbo and injector pump and youre in for around 10G's new.
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Old 05-02-2017, 08:20 PM   #16
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Counseling for your new found speed desires might be less expensive and more effective. It`s not just an engine change, it`s all the other changes that go with a different engine and accommodating it.
The suggestion of making sure everything else is optimized, like hull condition, prop,etc, is good.
Depending what changes, an easier but modest improvement would be swapping the FL120 for an FL135.
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Old 05-02-2017, 09:06 PM   #17
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Greetings,
Mr. F. Short answer. No, IMO. Not worth the time, expense or possible aggravation. Sell what you have and put the $$+the refit $$ into a faster vessel.
If I may ad to RT's spot-on input.

Shine your boat, sell your boat, purchase a really nice much faster (SD or P hull design) boat with lots o' creature comforts - including being able to move along at speeds you desire, whenever you desire.

Whether single screw or twins, whether D, SD or P hull... once you slow to just a bit below hull speed fuel use plummets [estimate 3 to 4 nmpg range] and cruising gets affordable. However, with SD or P hulls you can go pretty quickly at about [rule of thumb average here] 1 nmpg. Quick is not a word used in a D Hull's user manual.

Don't know where you live - but - may I recommend you look closely at Tollycraft planing hull boats. Very well built and a kick to own!

Happy Boating Daze - Art
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Old 05-02-2017, 11:17 PM   #18
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Keep the motor and add some outboard power for when you need it.....

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Old 05-02-2017, 11:26 PM   #19
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Quote:
Originally Posted by Fotoman View Post
I have a 1979 Marine Trader Europa Sedan with a FL 120 in it. Runs great but I'm starting to find it a bit slow. Against the wind and current (St. Lawrence River) I will often drop around 4 knots. I'd like to have a bit more power to never go under 6 and to reach 8-9 with no opposing forces.

Would putting in a new engine get me the extra speed I'm looking for or is it just wishful thinking?

There is a guy in my marina who has a MT 36 and repowered with a Volvo 200 HP (I think) and he goes significantly faster than me.

(No need to get into the cost debate at this point, just the rationale new engine vs speed).
Sorry to be a wet blanket, Fotoman, but even if money was no object I doubt you would gain much, even with a 210hp Cummins in there. I have the exact same vessel and engine, and I can just feel that there is more than enough power to reach over hull speed, but any faster than that would raise the fuel consumption so much I seriously doubt it is worth it, if the engine is otherwise ok.

If the engine had become so bad it was a throwaway..? But even then I doubt it, the boat in just too heavy and too short to realise the theoretically semi-planing capability. Better to save the money, sell her while the engine is still good, and, to use those iconic words..."get a bigger/faster boat"..!
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Old 05-03-2017, 08:43 AM   #20
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I for one believe you will benefit and like the additional power.
I have experience in powering up" an old boat. I had an old 34 Mainship and replaced the original anemic Perkins 160 with a Cummins 6BTA 270 and the additional ponies made a great boat an outstanding boat.
Originally it was an 8 know cruiser, topped out at 10.5.
After the repower it cruised easily at 13/14 knots and topped at 18.5.
And for those many times I cruised at the "original" 8 knot pace I got about 50% better economy measured in nautical mile per gallon.
I say power up.
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