MDI 30 Update

Towboat

Lieutenant
Joined
Jul 17, 2012
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50
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Location
Penobscot, ME
Thought I'd chime in here now that I have had the chance to put a hundred hours or so on the boat. There is not much information on these hulls so perhaps this may help someone who is looking at a similar boat someday. I will try to answer any questions anyone might have

Other than a near catastrophic engine disaster when the aftercooler core began leaking (fortunately at idle on the mooring), there have been no engine problems :eek:. I knew I should have gone though everything before really using the boat, but how bad could it be for just a couple months, right?? Yeah...lesson learned.

Anyway, I really like the boat overall. I'm getting an honest 4gph at 2K RPM which is right about 13kts. Bump it up to 2200 and I'm now into the turbo and substantially more fuel, but also about 16kts. Top speed is 22 - a little under propped I think, but I'm ok with that, no need to push it.

The hull rides great in head and following seas, but she is a little stiff on the beam. Wet, but no pounding at all. I was a little surprised to feel what I would assume to be some hull flex in a short, steep head sea. No pounding at all, just a little hull movement depending on how you hit each wave. These observations were made mostly in 2-4' and some 3-5' of the typical short, messy, confused fall Penobscot Bay chop.

I figured the boat would feel totally solid with no movement - my obsessive personality wants to worry about it, but it's survived 23 years and 2000 hours so It's fine I'm sure. Absolutely no evidence of any stress cracking anywhere. No idea about the hull thickness, but the displacement is 9-10K without many extras and with 4 big stringers she seems plenty stout. Guess I was just surprised to feel anything at all.

Boat rides very flat at speed - almost too flat. She's obviously designed to carry a deck load so when light it is a bit wet in a head sea. In recreational trim, all the weight is midship and forward with a finished cabin, two 8d's, forepeak water tank, etc. We'll see how she rides with a couple thousand pounds of people & dive gear next month.

Great boat for my purpose - maybe not the best for drifting due to the roll, but it also has very little gear on board so some extra weight from fishing gear might calm that down a bit.
 
Last edited:

BillD

Admiral
Joined
Sep 1, 2011
Posts
7,306
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2,904
Location
Portsmouth NH, boating out of the mighty Merrimack
Boat Make
25 Terry Jason with Cummins 370 power
Keep the Cummins 6BTA under propped

"Top speed is 22 - a little under propped I think, but I'm ok with that, no need to push it."

Important to note:

A 6BTA 330 should see NO LESS than 2900 WOT measured by photo tach on the flywheel or digital tachometer with the boat AS HEAVY as you'll ever run it.

A 6BTA 370 should see NO LESS than 3150 WOT same as above.

A 6BTA 260 (2600 rated) should see NO LESS than 2700, same as above.

Consider:

Add a "loss of raw water alarm" on the mixing elbow.

Add a "high temp coolant SWITCH" 205F with an alarm.

Borel Manuf makes a very nice panel and alarm with a band sender for the exhaust and you can tie the temp switch in to it.

Very cheap insurance....very cheap and very easy to install.

Just ask for help if you want it !! :D

FWIW, Bill D
 

Towboat

Lieutenant
Joined
Jul 17, 2012
Posts
50
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Location
Penobscot, ME
Thanks Bill,

This is actually a 300hp 6BTA-M rated at 2800 RPM. I can turn almost 2900 with full fuel. I definitely plan to add some gauges including the ones you mentioned as well as pyro & boost. Lots to do in the shop this winter! I was impatient and wanted to play...luckily it didnt cost me the engine!
 

BillD

Admiral
Joined
Sep 1, 2011
Posts
7,306
Likes
2,904
Location
Portsmouth NH, boating out of the mighty Merrimack
Boat Make
25 Terry Jason with Cummins 370 power
Thanks Bill,

This is actually a 300hp 6BTA-M rated at 2800 RPM. I can turn almost 2900 with full fuel. I definitely plan to add some gauges including the ones you mentioned as well as pyro & boost. Lots to do in the shop this winter! I was impatient and wanted to play...luckily it didnt cost me the engine!

Tow,

Just double checking on the 2900 with you.
Is the rpm by "photo tach" ?
I'm asking if the 2900 is accurate +-1 rpm:D
 

sandytows

Lieutenant
Joined
Sep 14, 2013
Posts
53
Likes
4
Hi Tim! Liking the new boat I see! you aren't gonna paint her red are you?
 

CCtuna

Rear Admiral
Joined
Oct 20, 2012
Posts
1,476
Likes
978
Location
Nauset
Boat Make
Some day...
Tow,

Youve got an awesome rig! Im a student at MMA so i drive by it like 10 times a day and i always though it was an Ellis. She's real clean too. Saw you out the other day during my ship-handling class and she moves pretty good!
 

rlalaw

Lieutenant
Joined
Jan 2, 2012
Posts
66
Likes
19
Boat Make
Padebco
i realize i'm 6 months late to this (I am on the water in the summer.. on line in the winter!) but congrats on the purchase... i had been looking at that listing for awhile but never made it up to see her. glad the engine issue wasn't more serious...
 

Towboat

Lieutenant
Joined
Jul 17, 2012
Posts
50
Likes
22
Location
Penobscot, ME
No worries - there's no expiration date on this thread. Thanks for all the positive responses. Boat is in my shop but there has been too much plowing going on and not enough working on it! A week without power didn't help things.

Hope everyone is having a nice holiday
 

oldshell55

Captain
Joined
Sep 27, 2013
Posts
653
Likes
162
Location
new york
Boat Make
BHM36 , 38’ young bros ,
No worries - there's no expiration date on this thread. Thanks for all the positive responses. Boat is in my shop but there has been too much plowing going on and not enough working on it! A week without power didn't help things.

Hope everyone is having a nice holiday

if your to be obsessive about anything, change the engine zinc to avoid the aftercooler and heat exchanger having future problems. good luck
 

Drifter

Lieutenant
Joined
Dec 31, 2017
Posts
81
Likes
32
Age
62
Thought I'd chime in here now that I have had the chance to put a hundred hours or so on the boat. There is not much information on these hulls so perhaps this may help someone who is looking at a similar boat someday. I will try to answer any questions anyone might have

Other than a near catastrophic engine disaster when the aftercooler core began leaking (fortunately at idle on the mooring), there have been no engine problems :eek:. I knew I should have gone though everything before really using the boat, but how bad could it be for just a couple months, right?? Yeah...lesson learned.

Anyway, I really like the boat overall. I'm getting an honest 4gph at 2K RPM which is right about 13kts. Bump it up to 2200 and I'm now into the turbo and substantially more fuel, but also about 16kts. Top speed is 22 - a little under propped I think, but I'm ok with that, no need to push it.

The hull rides great in head and following seas, but she is a little stiff on the beam. Wet, but no pounding at all. I was a little surprised to feel what I would assume to be some hull flex in a short, steep head sea. No pounding at all, just a little hull movement depending on how you hit each wave. These observations were made mostly in 2-4' and some 3-5' of the typical short, messy, confused fall Penobscot Bay chop.

I figured the boat would feel totally solid with no movement - my obsessive personality wants to worry about it, but it's survived 23 years and 2000 hours so It's fine I'm sure. Absolutely no evidence of any stress cracking anywhere. No idea about the hull thickness, but the displacement is 9-10K without many extras and with 4 big stringers she seems plenty stout. Guess I was just surprised to feel anything at all.

Boat rides very flat at speed - almost too flat. She's obviously designed to carry a deck load so when light it is a bit wet in a head sea. In recreational trim, all the weight is midship and forward with a finished cabin, two 8d's, forepeak water tank, etc. We'll see how she rides with a couple thousand pounds of people & dive gear next month.

Great boat for my purpose - maybe not the best for drifting due to the roll, but it also has very little gear on board so some extra weight from fishing gear might calm that down a bit.
 

Drifter

Lieutenant
Joined
Dec 31, 2017
Posts
81
Likes
32
Age
62
Happy new year . I am refurbishing a 91 30' mdi and would like to talk with about yours sometime.
 
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