Mainship 36

Tomorrow morning we will be seriously looking at a 1986 Mainship 36' Aft Cabin.

Question..........What is the hull speed for this boat and how economical (MPG) would*it be*at 6 to 7 knots with twin 270HP gas engines?

Coming from a sailboat, I know fuel will cost money and I have accepted that. I know it will be affordable but was just wondering about fuel economy.

*

Thank in advance

*

Tony B

I don't know but I would think in the 3 - 5 mpg range.

Not considering a diesel?

Haven't done the math on ours but I've been told that the blue 270's run about 6 gph per engine under 3,000 to 3,200K rpm (at which rpm the secondaries open up). *I'll get up to around 9-10 knts at just under 20,000K rpm. *The boat feels like the sweet spot is around 1,800 rpm. *When the secondaries open, I'm told that this jumps to 12 gph per engine per hour. *I have yet to get above 3,000 for any long period of time nor approach WOT.

*

Question..........What is the hull speed for this boat and how economical (MPG) would*it be*at 6 to 7 knots with twin 270HP gas engines?

Click to expand...

*To calculate the hull speed.

*Take the square root of the waterline.

If it is 36 that is* 6

multiply by 1.34 to get 8.04

There you go.

Faster than that and you are just pushing water and burning fuel.

SD

*


-- Edited by skipperdude on Thursday 2nd of February 2012 04:55:22 PM

Rick in the Delta wrote:
*I'll get up to around 9-10 knts at just under 20,000K rpm.

Click to expand...

*Wow! Motorcycle engine?

And FYI...it is a planing hull....or at least a semi-planing hull. I would recommend diesel!!!

Oops! *Not paying enough attention to editing.......

*

The hull is "semi-displacement" which, of course, means it does neither displacement or planing very well. *The origional specs at at*http://www.mainship.com/models/previous_models/36dc.htm

I'm new to this boat, still, but I find the speed estimates a bit inflated and at the least they are expensive and working the small *blocks way hard.

20,000 rpm - more like Formula 1... probably would burn about 20gpm :-D

Interested if there are any more updates and new comments on this thread from current crusader 270 hp owners as I am considering the same boat and have the same questions. Clearly earlier poster meant 2000 rpm not 20000. Thanks in advance,

timjet said:

Not considering a diesel?

Click to expand...

Baker said:

And FYI...it is a planing hull....or at least a semi-planing hull. I would recommend diesel!!!

Click to expand...

Old thread, but...


Don't think Mainship offered diesels in that model. At least never saw one advertised....

Our Mainship 34 Mk III was an '87 and their 34 models of that era were all single diesel. I never understood why they only (apparently, at least AFAIK) offered gas in the 36s.

There was a 40, too, but I can't remember engine options for those...

-Chris

ranger42c said:

Old thread, but...


Don't think Mainship offered diesels in that model. At least never saw one advertised....

Our Mainship 34 Mk III was an '87 and their 34 models of that era were all single diesel. I never understood why they only (apparently, at least AFAIK) offered gas in the 36s.

There was a 40, too, but I can't remember engine options for those...

-Chris

Click to expand...

I saw one 36 with twin Perkins 200. Also saw a couple of 40s with twin Perks.
But they are rare.

We've got a 40 with twin perks. There are a few others with gas I've seen floating around. We "trawler"it up most of the time at 7 or 8 kts burning 3-4 gph.

The 36 came with twin 4 cylinder perkins, the 4.236, I believe. The 40 came with twin 6.354. In later years, they used the 8.2 L Detroits.

I cant believe they fit anything bigger than these perks in there! my radiator caps and turbo "horn" are literally pressing against the hatch when it's closed. are the 8.2s squat or what?!

slowandsteady said:

The 36 came with twin 4 cylinder perkins, the 4.236, I believe. The 40 came with twin 6.354. In later years, they used the 8.2 L Detroits.

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I have seen scores of 36 aft cabin Mainships. Never saw one with twin 4 cyl Perkins. Only the one with the twin 200s, or gas 350s.
Never saw a 40 aft cabin with Detroits. Only Perkins. Or gas 454s..
All of the 40 Pilot House models had the original 160hp version, then the later ones had the 165 hp or 200 hp Perkins.

I won't argue with you jleonard because you have been around boats way longer than I and now you've placed some doubt in my mind. But when I first started looking at Mainships I lusted after one that I saw on YW that I am almost sure had twin 4 cylinder Perkins in it. The 36 on YW now has new DD 8.2, not factory. Would Mainship really put twin 200 Perkins in that hull? Wait, they put twin Crusaders in them, I think I just answered my question. Maybe you're right...

We are Living aboard and cruising on one.

Luke-44 said:

Interested if there are any more updates and new comments on this thread from current crusader 270 hp owners as I am considering the same boat and have the same questions. ,

Click to expand...

Luke

I dont have the time or energy to answer all your questions tonight.
I am retired so call me tomorrow, any reasonable time (EST) and I can answer all of your questions. I am sending you a pm with my cell number.
If I dont hear from you, I will post the answers on here when I can.

Slow & steady I am not counting repowered. The field is open there.
I know of some who used twin Yanmars for example.

Fuel Economy

This is an older post but has been renewed.

After I bought the 1986 Mainship 36 DC, I joined a Mainship Group on Yahoo Groups.

On there I came on contact with an owner of an identical boat to mine. he had traveled the Great Loop for 6500 miles.
He kept meticulous records using Flow Scan meters for the entire trip.

He sent me the data attached.
It turned out to be very accurate for me, although I don't have flow scan meters. I checked my mileage and fuel consumption and come up with the same figures.

One More Chart

Since I had planned a long trip, I did the following calculations based on the info on the preceding charts. This chart was designed specifically for me and on the current price of gas at the time.
We generally travel on one engine at a time at 7 SMPH. We knew that traveling from Houston, Tx area to Mississippi (our first goal) could be problematic in the way of few gas stops and marinas. This new chart would help determine if speeding up would be economically worth while or would we run out of gas.
This chart had been invaluable for decision making as we traveled approx. 2,000 miles so far. I will update it in the next month or so to reflect the new price of gas.

Hi tony it was good chatting with you and I appreciate the work you have done to compile the gas mileage info.

But I can't seem to figure out gallons per hour at say 7-8 knots. I know it's in there (mpg) but I'm missing how to convert it. Thanks in advance, Bruce

Look at 8 knots and see how many MPG you get, which is also 8 Nm traveled in one hour.
If for instance you get 1.75 mpg, just divide the 8 miles by the 1.75 mpg and you get 4.6 gallons used.
If you want to double check your figures, multiply the 4.6 gals by the 1.75 mpg and that will give you 8 miles.

I personally never count gals/hour. I always think in miles. I check my gas tanks and I see 50 gals minus 10 gals from empty and I have 40 usable gallons left. At 7-8 kts, I know I that at 1.75Mpg I can go 70 miles on 40 gals before running on fumes.
All of this is assuming no real adverse current or wind. I use a dipstick I made to accurately measure gas. I mean more accurate than any gauge, which I never trust.

When I buy my next load of fuel in a mont or so, I will give you the updated chart.

Feel free to call anytime between 8AM and 8PM EST- I am retired, so no problem.

We just took possession of a '87 36' DC two days ago.
Twin 270 Crusaders.
Boat was a floating cottage last few yrs so have much to do.

I am quite interested in this discussion on performance.
We did a sea trial and while the tachs were working we ran a simulated cruise speed @ 3000 -3200.
Hull ran good/felt good but no speed measuring instruments on board.

Seat of pants said 14-15 which sounds way optimistic based on this thread???

I googled this boat and ended up here and joined.

I'm 57 yrs old, boated all my life, built, raced etc.
I am way impressed w/what I've seen so far.
Design and construction appear to be over the top.

I too was concerned w/the small blocks in so big/heavy boat.
The semi displacement hull designed led me to take the leap.

One motor rebuilt.
In watching/listening to motors under way, I am concerned about water reversion under way.

I have much reading to do but wanted to say Hi, and thank the many knowledgable authors on this thread.

Great reading.

Thanks!
Gary

If you have a smartphone, download the Navionocs boating app. You can get tour speed in there via GPS and record your track and speed

Gary...
Welcome aboard TF
You will find most folks friendly & helpful

Have you searched online for that model?
You should be able to find published performance specs.

Gary

I have a 1986 Mainship 36DC. We live-aboard and cruise on it full time.
Go back to page 1 of this thread and look at posts 19 and 20. This should give you all the info you want.
You should plane nicely at about 13-17 MPH and top out at a little over 20 with an average load.

Also, there is a Mainship group on Yahoo Groups that is specific to Mainships only. Here is the link: www.groups.yahoo.com/neo/groups/mainship

1986 Mainship DC

I have twin Crusader 350 cu in engines and find that at 2500 rpm I consume 6 gallons per hour. Engines actually seem to be the happiest at around 1800 rpm. That's where they seem to operate the smoothest. In calm water conditions 2500 rpm gives me 7 to 8 knts. My boat is no speed demon but her comfort underway and at the dock make up for any shortcomings in speed.

Greetings,
Welcome aboard Mr. j.

Thanks for all the help guys and sorry I missed your replies. Somehow wasn't getting notices.

Have been working away at my to do list each weekend and making headway.

Will start a new thread so as not to clog up this one.

Thanks again guys.
And Gmarr, I have an i-phone.

Taking a hand held GPS next weekend.

Gary

Tony B said:

Go back to page 1 of this thread and look at posts 19 and 20.

Click to expand...

Skimmed first and just took the time to reread and digest the info.
WOW!

Thank you sir.
Also just printed all 3 graphs.