Reply
 
Thread Tools Search this Thread Display Modes
 
Old 03-31-2022, 02:03 PM   #1
Senior Member
 
Waterant's Avatar
 
City: Woodbridge
Vessel Name: DORA
Vessel Model: 2002 Mainship 430
Join Date: Oct 2018
Posts: 268
Rebuild vs Repower

I need your opinion on something:

I've got 2002 Mainship 430 with twin Yanmar 6LYA 370 Hp engines.
Engines do not run and there is a good possibility they need a full rebuild - I do not have all the details yet and evaluating my options for the worse case.

A full rebuild of those engines will be around $60k
Removing them and putting in brand new Beta 80T engines will be around $60k
* If I'm off in those numbers, let's say the cost of the project will be the same, whatever it will be.

Pros for replacing Yanmars with Betas are:

- much simpler and smaller engines - I like working on the engines and being able to fix everything myself is a big plus. those Yanmars seem to be much more complex and not much space in the engine room to work around them.

- triple fuel efficiency and the range - I like to go slow and far so fuel efficiency is much more important to me than having the ability to run at 20knots from time to time. I know Yanmars can be run at 1200RPM but this is not good for them and they still use 10 mpg at 7-8 knots.

- I want to finish my Great Loop and 5500 miles at 1 mpg with Yanmars vs 3 mpg (or possibly better) with 80T Betas @$6 per gallon will be $33,000 vs $11,000 for fuel.
So, it's like $10k savings in fuel cost every year (I like to go far and see new places every season) which is 60-90 nights at decent marinas every year.


Cons of replacing Yanmars with Betas are:

- Possible loss of boat value, because those were built as "fast trawlers" (if there is such a thing), and a lot of potential buyers, want the ability to run at 20 knots when needed.

- Wrong weight distribution which will probably require adding extra ballast or tankage because of the difference in weight of smaller motors vs larger ones.

- The whole engines replacement project will take much longer with lots of challenges to overcome.


Did I miss something?
What would you do?
__________________
WaterAnt
2002 Mainship 430
https://www.trawler.life
Waterant is offline   Reply With Quote
Old 03-31-2022, 02:16 PM   #2
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 5,037
What are the specs on the Beta engines? I’m not familiar with them.
Normally I would say go new because a rebuild CAN be a crapshoot (even from.a good shop). But I don’t know the Beta and personally I have my doubts about being 3 times more efficient. And that seems to be what you are banking on
__________________
Jay Leonard
Ex boats: 1983 40 Albin trunk cabin, 1978 Mainship 34 Model 1
New Port Richey, Fl
jleonard is offline   Reply With Quote
Old 03-31-2022, 02:17 PM   #3
Guru
 
City: Owings, Md
Vessel Name: Graceland
Vessel Model: Mainship 34 MK1
Join Date: Jan 2016
Posts: 1,381
I would expect the Betas to lower resale value only because it would make marketing the boat weird. The Betas are good engines but most people shopping for Mainship 430's have already selected that model and expect it to be similarly equipped to other 430's. There are certainly trawler shoppers who are happy with displacement only, but your boat wouldn't be on their radar because that model is known to be a semi-displacement boat.

I would expect that any fuel savings would be well surpassed by resale loss.

The Yanmar 370's are well regarded engines, seems odd that a full rebuild is required for both, did it sink?
Gdavid is offline   Reply With Quote
Old 03-31-2022, 02:43 PM   #4
Guru
 
Benthic2's Avatar
 
City: Boston Area
Join Date: Feb 2017
Posts: 2,610
Would it make sense to consider replacing with a lower powered Yanmar ? That may save some complication ( and cost ) as all your engine controls, transmission bolt patterns, exhaust location etc. are more likely to be compatible.

If you go with the Betas, will you be able to use the same transmissions ?
Benthic2 is offline   Reply With Quote
Old 03-31-2022, 03:04 PM   #5
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,187
Have you gotten firm bids on the replacement costs? These type of projects can spiral out of control as far as cost and time goes. If you were putting the same engines back in it would be a fairly simple job, but with different engines everything changes. Transmissions, motor mounts, exhaust, wiring, gauges, controls, etc and more will all have to change and some of it custom made. Think long and hard. Good luck with whatever way you go. Keep us informed and we WILL need photos along the way.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 03-31-2022, 03:04 PM   #6
Senior Member
 
Solly's Avatar
 
City: Solomons MD.
Vessel Name: Sun Runner
Vessel Model: 1985 Mainship 34 Trawler MK III
Join Date: Mar 2018
Posts: 488
Rebuild.
If the manufacture thought 80 hp engines in there were a good idea they would have put them in. Seriously doubt if you'll see that much increase in mpg. Props will probably need to be changed.
If you have to, rebuild and sell, then get what you want.
Solly is offline   Reply With Quote
Old 03-31-2022, 03:14 PM   #7
Senior Member
 
Waterant's Avatar
 
City: Woodbridge
Vessel Name: DORA
Vessel Model: 2002 Mainship 430
Join Date: Oct 2018
Posts: 268
> What are the specs on the Beta engines?

Those are based on Kubota engines. https://betamarineusa.com/portfolio/beta-85t/
Because those are only 80-85 hp, they will be in the perfect working range for 8 knots hull speed vs idle RPM of 370 hp engines.

> Would it make sense to consider replacing with a lower powered Yanmar ?

As I know, the cost of new Yanmars will be much higher even if I go with smaller engines.

> If you go with the Betas, will you be able to use the same transmissions?

The quote I've got for new Betas includes transmissions but they said i may be able to use the existing ones.
Betas are marketed specifically for repowering and come with custom engine mounts to fit the existing beds.
In any case, I will probably will need new props for Betas because all the power/toque/RPM curves are different.

> I would expect that any fuel savings would be well surpassed by resale loss.

yes, this might be the biggest issue with repowering to the smaller engines but on the other hand, there are a lot of Mainship owners who always go slow. plus higher diesel prices may push even more people away from running fast so why not go slow even more efficiently than running 2x 400 hp engines at idle speeds?
And the living space and accommodations of Mainship are much better than my former "true" trawler (Defever 41) with a small single-engine.


> The Yanmar 370's are well regarded engines, seems odd that a full rebuild is required for both, did it sink?

The boat took some water because of the clogged drains and failed bilge bumps but the water did not reach the engine blocks. also, the engines were not winterized properly at some point so some parts of the raw water system may have to be replaced. I really hope there will be no need for a full rebuild but preparing for the worse case.
__________________
WaterAnt
2002 Mainship 430
https://www.trawler.life
Waterant is offline   Reply With Quote
Old 03-31-2022, 03:31 PM   #8
Valued Technical Contributor
 
DavidM's Avatar
 
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,785
Comments in bold below:

QUOTE=Waterant;1089357]I need your opinion on something:

I've got 2002 Mainship 430 with twin Yanmar 6LYA 370 Hp engines.
Engines do not run and there is a good possibility they need a full rebuild - I do not have all the details yet and evaluating my options for the worse case.

A full rebuild of those engines will be around $60k
Removing them and putting in brand new Beta 80T (Don't see an 80T, 85T yes) engines will be around $60k
* If I'm off in those numbers, let's say the cost of the project will be the same, whatever it will be.

Pros for replacing Yanmars with Betas are:

- much simpler and smaller engines - I like working on the engines and being able to fix everything myself is a big plus. those Yanmars seem to be much more complex and not much space in the engine room to work around them

The Yanmar does have a turbocharger and an after cooler and the after cooler needs a full service job every 3-5 years depending on what kind of water you cruise in. Took me about a day plus $100 in valves. Otherwise I don't see much different than the Beta.

- triple fuel efficiency and the range No, No and No. I ran my Yanmar 370 at 1,400 rpm and it burned 2 gph making 30 hp each. A pair of Betas will do maybe 10-15% better at that power level - I like to go slow and so fuel efficiency is much more important to me than having the ability to run at 20knots from time to time. I know Yanmars can be run at 1200RPM but this is not good for them and they still use 10 mpg at 7-8 knots. 1,400 rpm is about as slow as I would run them. Run them up to 2,500 for 5 minutes every eight hours to blow out accumulated carbon
- I want to finish my Great Loop and 5500 miles at 1 mpg with Yanmars vs 3 mpg (or possibly better) with 80T Betas @$6 per gallon will be $33,000 vs $11,000 for fuel. No, see above. You might save $2,000.
So, it's like $10k savings in fuel cost every year (I like to go far and see new places every season) which is 60-90 nights at decent marinas every year.


Cons of replacing Yanmars with Betas are:

- Possible loss of boat value, because those were built as "fast trawlers" (if there is such a thing), and a lot of potential buyers, want the ability to run at 20 knots when needed. Big loss of value. I wouldn't buy that boat with those engines. Not many would either. At best you would get the normal market value less the cost of replacing the Betas with Yanmars.

- Wrong weight distribution which will probably require adding extra ballast or tankage because of the difference in weight of smaller motors vs larger ones.

- The whole engines replacement project will take much longer with lots of challenges to overcome.

Did I miss something?
What would you do?[/QUOTE]

You have totally mis calculated the efficiency of the Yanmar vs the Beta at low power output. Yes it does take more power to move the internals of a 5 liter engine vs a 3 liter one, but no where near the numbers you are figuring. That plus loss of resale value makes it an unwise move to replace the Yanmars with Betas.

I am attaching the data sheet for the Yanmar 370. Compare its fuel consumption at 40 hp with the Beta. There isn't that much difference.

And finally what makes you think that the Yanmars are trash. It takes something catastrophic like loss of oil pressure while running hard and seizing up to completely trash an engine that young. Even a severe overheating shouldn't cost more than $10 grand to fix.


David
Attached Files
File Type: pdf Yanmar 6LYA-STP Datasheet.pdf (791.1 KB, 14 views)
DavidM is online now   Reply With Quote
Old 03-31-2022, 03:37 PM   #9
Guru
 
Benthic2's Avatar
 
City: Boston Area
Join Date: Feb 2017
Posts: 2,610
What if you just rebuilt one Yanmar and ran on one engine all the time ? That would get the engine RPM up into your desired range but still allow you the fuel savings and slow speed you are after ?

I know it's not an ideal solution but if it can cut a $60k repair bill in half, it might be worth considering.
Benthic2 is offline   Reply With Quote
Old 03-31-2022, 03:45 PM   #10
Senior Member
 
Waterant's Avatar
 
City: Woodbridge
Vessel Name: DORA
Vessel Model: 2002 Mainship 430
Join Date: Oct 2018
Posts: 268
> If the manufacture thought 80 hp engines in there were a good idea they would have put them in.

Possibly but that was in 2002 when the diesel was $1.5 per gallon (remember those good old days?)
and Mainship got bankrupt a bit later, so they may not be right after all.


> Seriously doubt if you'll see that much increase in mpg.

here is my logic:

from what i could find, 1700 RPM is what the owners of Mainship 430 with the same Yanmars are running to get the fuel efficiency at 8 knots

Yanmar 6LYA at 1700 RPM processes 50 kW of power @ 3 gph of diesel consumption
https://www.trawlerforum.com/forums/...6&d=1613510108

Beta 85T processes the same 50 kW of power at 1900 RPM @ 5 Lph or 1.3 gph of diesel consumption
https://betamarineusa.com/wp-content...ower-Graph.pdf
and I still have 20% of power in reserve to compensate for the wind and current and still maintain the hull speed.

so, I'm looking at the total of 6 gph vs 2.6 gph for the same 50 kW of output power.
yes, props will have to be replaced but getting more than doable efficiently may be worth the trouble.


> If you have to, rebuild and sell, then get what you want.

Good option, but I want a low-maintenance boat with no wood outside with the layout of Mainship 430 and the range of a Selene. Putting small diesels into Mainship 430 will get me very close to my perfect boat for way less than the cost for Selene 43.
I do understand that repowering will take a lot longer with lots of issues to resolve so it's not an easy decision.
__________________
WaterAnt
2002 Mainship 430
https://www.trawler.life
Waterant is offline   Reply With Quote
Old 03-31-2022, 04:06 PM   #11
Senior Member
 
Waterant's Avatar
 
City: Woodbridge
Vessel Name: DORA
Vessel Model: 2002 Mainship 430
Join Date: Oct 2018
Posts: 268
Quote:
Originally Posted by DavidM View Post
No, No and No. I ran my Yanmar 370 at 1,400 rpm and it burned 2 gph making 30 hp each. A pair of Betas will do maybe 10-15% better at that power level
I was writing my assumptions at the same time you sent this.

on the power graph, there is no 1400 RPM for Yanmar but looks like the data is almost the same as for 1700 RPM (the lowest on the graph)

Yanmar 6LYA at 1700 RPM processes 50 kW of power using 3 gph of diesel
https://www.trawlerforum.com/forums/...6&d=1613510108

Beta 85T produces the same 50 kW of power at 1900 RPM using 5 Lph or 1.3 gph of diesel
https://betamarineusa.com/wp-content...ower-Graph.pdf

so, I'm looking at the total of 6 gph vs 2.6 gph for the same 50 kW of output power.

maybe I'm missing something but those are the numbers I see on those graphs and do not have any reason not to believe them.

Quote:
Originally Posted by DavidM View Post
And finally what makes you think that the Yanmars are trash. It takes something catastrophic like loss of oil pressure while running hard and seizing up to completely trash an engine that young. Even a severe overheating shouldn't cost more than $10 grand to fix.
I should know more next week but for now, I'm assuming a full rebuild at the estimate I've got so far and I'm evaluating my options.
if the problem will cost $10k to fix, I'll be the happiest boat owner of the month.

> What if you just rebuilt one Yanmar and ran on one engine all the time ?
> That would get the engine RPM up into your desired range but still allow you
> the fuel savings and slow speed you are after ?

my OCD (or whatever this condition is called) will drive me crazy very fast if i have only half of something working while another half is broken
__________________
WaterAnt
2002 Mainship 430
https://www.trawler.life
Waterant is offline   Reply With Quote
Old 03-31-2022, 04:27 PM   #12
Senior Member
 
Slowmo's Avatar
 
City: Lafayette, CA
Vessel Name: Esprit
Vessel Model: 40' Tollycraft tricabin diesel
Join Date: Oct 2018
Posts: 453
I think DavidM pretty much hit the nail on the head. The thermal efficiency differences between the two engines simply can't be as big as you assumed. Just from a pure engineering view the difference of 10-15% is about what you should expect.

Rebuilding guarantees you that you won't have any difference in fitment, weight, or performance. Changing the engine you will find lots of things need changing to adapt to the new engine which will cost you more in the end. My only hesitation is why the Yanmars died in the first place, 2002 isn't old for a boat.
Slowmo is offline   Reply With Quote
Old 03-31-2022, 04:32 PM   #13
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,187
I would not just do one engine. The boat will be a PITA to handle. And if you get into challenging conditions it could be even worse. And the resale value will be in the dumper.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 03-31-2022, 04:44 PM   #14
Senior Member
 
Waterant's Avatar
 
City: Woodbridge
Vessel Name: DORA
Vessel Model: 2002 Mainship 430
Join Date: Oct 2018
Posts: 268
Quote:
Originally Posted by Slowmo View Post
Just from a pure engineering view the difference of 10-15% is about what you should expect.
I would expect as much if someone ask me without any data but looking at the power charts of both engines for the same 50 kW output you can see a huge difference in consumption. I do not think Beta would publish deceiving information.
or maybe I'm missing something on the chart but it seems to be 5 Lph or 1.3 gph for 50 kW of power at 1900 RPM on Beta 85T vs 3 gph at 1700 RPM for the same 50 kW on Yanmar 6LYA.

Quote:
Originally Posted by Slowmo View Post
My only hesitation is why the Yanmars died in the first place, 2002 isn't old for a boat.
This is a $60000+ question but I do not have enough details right now to ask for help in that direction.
__________________
WaterAnt
2002 Mainship 430
https://www.trawler.life
Waterant is offline   Reply With Quote
Old 03-31-2022, 05:00 PM   #15
Guru
 
kchace's Avatar
 
City: Brookline, NH
Vessel Name: Shalloway
Vessel Model: Defever 44, twin Perkins
Join Date: Sep 2013
Posts: 2,260
When comparing power curves, it appears you’re using max power on the Beta curve and propeller power on the Yanmar curve. If you look at max power on the Yanmar curve it’s actually producing 125kw at 1700. And using the propeller curve on the Beta requires 2200 rpms and 9lph to achieve 50kw output.
kchace is offline   Reply With Quote
Old 03-31-2022, 05:13 PM   #16
Senior Member
 
Waterant's Avatar
 
City: Woodbridge
Vessel Name: DORA
Vessel Model: 2002 Mainship 430
Join Date: Oct 2018
Posts: 268
Quote:
Originally Posted by kchace View Post
When comparing power curves, it appears you’re using max power on the Beta curve and propeller power on the Yanmar curve. If you look at max power on the Yanmar curve it’s actually producing 125kw at 1700. And using the propeller curve on the Beta requires 2200 rpms and 9lph to achieve 50kw output.
thanks. i suspected I was missing something there. 4.6 gph is still better than 6 gph (25% more efficient?) but not as sexy as 2.6 vs 6.
__________________
WaterAnt
2002 Mainship 430
https://www.trawler.life
Waterant is offline   Reply With Quote
Old 03-31-2022, 05:44 PM   #17
Guru
 
Ken E.'s Avatar
 
City: Bellingham WA
Vessel Name: Hatt Trick
Vessel Model: 45' Hatteras Convertible
Join Date: Nov 2016
Posts: 1,973
Have you looked into remanufactured Yanmar engines? I was curious if they were available since I used remanned Cummins on my repower and they turned out fine, including a new-engine warranty. Remanned Yanmars are available from MECO, macdonaldequipment.com. I know nothing about their prices or real-world experience with these engines, only that they are being advertised by MECO.
__________________
Ken on Hatt Trick
Ken E. is online now   Reply With Quote
Old 03-31-2022, 05:46 PM   #18
Guru
 
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,186
Ant, some thoughts:

Not all "rebuilders" are created equal. Is the rebuild you're contemplating being quoted by a recognized Yanmar dealer that can offer a full warranty? Where is the vessel located? If not done already and you're on the East Coast, Mac Boring is one outlet to get some numbers from. As mentioned by others, some luck may be in your favor provided the motors didn't swallow water and then sit.

A removal rebuild offers the opportunity to make the ER a showpiece. David Marchand knows Yanmars pretty well, listen to him carefully if you choose the rebuild route. Also check into boatdiesel for some detailed Q&A.
sunchaser is offline   Reply With Quote
Old 03-31-2022, 06:04 PM   #19
Guru
 
High Wire's Avatar
 
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,964
What exactly is wrong with the Yanmars? Has a professional said they BOTH need to be rebuilt?
If it were me, I would fix both engines, sell the boat and buy what you really want.
__________________
Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
High Wire is offline   Reply With Quote
Old 03-31-2022, 06:20 PM   #20
Guru
 
motion30's Avatar
 
Join Date: Jan 2010
Posts: 1,181
My 2 cents for what it is Worth

That boat would be more attractive to me with the smaller motors. Although I question the fact that the cost will be similar between new and rebuilt .of course I am aware of the high prices yamar charges for parts. Of course with new motors be moving away from those issues
If your numbers are correct I would be in favor of the smaller motors
motion30 is online now   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 03:28 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012