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Old 06-11-2017, 02:15 AM   #1
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Repower possibility 79 mainship 34 MK1

Hey guys.
Ship currently has a t6.354 w/7000 hrs and a leaking head gasket(oil )
Seen this today and looked like a good deal compared to a 1000 head and valve rebuild(might as well if im changing gasket) has anyone fit one of these into a MK1?
Volvo TMD 70B 200hp diesel marine engine, good running takeout - approximately 3500 hours on major rebuild, includes spare parts, can hear it run.
Itd be a jump up in HP frpm 165 to 200 so a little more speed out of it. Not much. And would this bolt up to my velvet drive (1.9 :1)Any thoughts welcome
Thanks
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Old 06-11-2017, 04:27 AM   #2
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A head gasket is a lot easier to replace than an entire engine! How's your Perking running otherwise? From what I've gathered, &k hours on a 6-354 that's been maintained isn't an excessive amount of time.





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Old 06-11-2017, 07:11 AM   #3
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Agree that fixing existing is likely to be cheaper and easier than repowering. Don't assume that the current motor has standard rotation. My boat had a counter rotating motor originally - as near as I can tell Mainship used either on the original 34 and just matched the prop (LH vs RH).
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Old 06-11-2017, 07:51 AM   #4
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Hummm. I think I'd rebuild. But what do I know.
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Old 06-11-2017, 08:40 AM   #5
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That boat could use more power so the 200hp sounds like a plan. You may get more than a little speed but it may require working the engine and bellying up to the fuel bar.

But as stated simply fixing is the only smart thing to do unles you've got more money than I suspect. So have at it.
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Old 06-11-2017, 10:34 AM   #6
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Believe I'd fix the Perkins and call it good.

The Volvo-Velvet Drive connection would be a big deal; if it's not a perfect match, then you're talking new gear, maybe shaft... plus all that extra work to do the swap, on top of all the work to change the engine...

When we had our Mainship III with 220-hp DD 8.2T.... the boat wasn't a speed demon.

That Perkins would probably one last another 72 years, though...



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Old 06-11-2017, 12:27 PM   #7
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make certain the velvet drive can take the higher torque. They have a lower upper HP and torque limit for diesels than for gasoline power. Google it and you can find the chart. I know you'd be going from diesel to diesel, just saying.
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Old 06-11-2017, 01:00 PM   #8
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3500 hours is a lot of hours and depends on it's maintenance and how it was operated. It's po found it wanting. Many turbo engines are near worn out with those hours. The specs I have indicate 192hp @2500 pleasure rating and 156hp @ 2000 commercial (continuous). How was it used? It's been rebuilt once you know of. The lower hp is where you'll need to top out an older engine to get much more life out of it.
In the long run, considering install changes, motor mounts, alignment, fuel-water-electrical-exhaust, it would be cheaper to rebuild the engine you have now.
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Old 06-11-2017, 01:14 PM   #9
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Quote:
Originally Posted by Alaskasbear View Post
Hey guys.
Ship currently has a t6.354 w/7000 hrs and a leaking head gasket(oil )
Seen this today and looked like a good deal compared to a 1000 head and valve rebuild(might as well if im changing gasket) has anyone fit one of these into a MK1?
Volvo TMD 70B 200hp diesel marine engine, good running takeout - approximately 3500 hours on major rebuild, includes spare parts, can hear it run.
Itd be a jump up in HP frpm 165 to 200 so a little more speed out of it. Not much. And would this bolt up to my velvet drive (1.9 :1)Any thoughts welcome
Thanks
You should ask on Boatdiesel.
My BW Velvet drives are currently bolted to Volvo TAMD41s.
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Old 06-13-2017, 12:52 AM   #10
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Quote:
Originally Posted by ranger42c View Post
Believe I'd fix the Perkins and call it good.

The Volvo-Velvet Drive connection would be a big deal; if it's not a perfect match, then you're talking new gear, maybe shaft... plus all that extra work to do the swap, on top of all the work to change the engine...

When we had our Mainship III with 220-hp DD 8.2T.... the boat wasn't a speed demon.

That Perkins would probably one last another 72 years, though...



-Chris

Thanks for all the fantastic replies. Think I'll just go with the head job this winter. Other than the leaking head it runs great. I was just looking at the increased HP scenario. I'll be fine staying at what i have now. After all the boats name is Slow Goin. Hate to contradict that.
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Old 06-13-2017, 05:54 AM   #11
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You didn't specify age of the Volvo . If its an older engine your likely to have parts availability issues. Volvo is known for lack of support on legacy engines.

I think i would change head gasket (on Perkins) and run until rebuild required.
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Old 06-13-2017, 07:53 AM   #12
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Repowering could cost a lot more than you expect. Unless you are lucky you will have to rework the engine beds and as others have said buy a new transmission. The higher horsepower will likely also require a new shaft and you will certainly need to at least repitch the existing prop if not replace it. If you have to go to a bigger shaft a new prob will be in the works. You could easily spend more on the things above than on the newer engine.
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