Question on the transom of my "New Boat"

MTboatguy

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Well I picked this little 14' Mirrocraft Sportsman up last summer, to take the motor off and put on my 14' fishing boat, got that all converted over to a tiller steer. Now I am sitting here looking at the Mirrocraft again and wondering if I should put it back in the water. I have corresponded with Mirrocraft and they have identified it as a Sportsman model that was rated at 45 hp, great I have 2 Evinrude 40hp big twins, so I want to put one of those on it. Problem is, the boat is a long shaft boat that somebody took a sawzall to and cut the transom down for a short shaft motor, again, not much of a problem, I have short shaft motors. Now my question is, how to approach redoing the transom with its cut down size, to ensure it will still handle the 40hp motor, I am thinking cutting those few inches of the transom wood and aluminum may have weekend the transom wood, so I am going to laminate new marine plywood and build a new one, then configure a cap to go over it.

Any suggestions? on how to make sure it is strong enough for the older heavier 40hp motor?

Thanks for any ideas you might have.
 

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Woodonglass

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If the wood is 1.5" thick and still solid I'd put 2-3 coats of paint on her and hang the motor. Those big ole' Knee Braces will ensure that the 40hp is NO PROBLEMO as far as weight
 

MTboatguy

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Thank you Sir, Just wanted to make sure, it is in fact a bit over 1.5 inches and it is solid, fortunately, the slathered the top of what they cut with a thick coat of resin, so it is sealed with plastic, but I am going to build an aluminum cap to cover the area like I did on my fishing boat.
 

64osby

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Are you talking about building a new transom for a long shaft? or using as is with a short shaft and adding a cap?
 
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MTboatguy

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No, I don't have any long shaft motors, everything I own is short shaft, so I just want to make sure I could get this one stout enough to handle one of those old Evinrude big twins, they weigh a ton! Then I would build a contoured edge cap to cover the top of the wood and hold the aluminum skin to the transom wood.
 

pckeen

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To add additional strength, you can add (if the boat doesn't already have one), a plywood plate on the back of the boat that is larger and goes down further than the existing wood.
 

bonz_d

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Best of luck with your new project MT, those old Evinrudes just keep hangin around don't they!
 

MTboatguy

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Best of luck with your new project MT, those old Evinrudes just keep hangin around don't they!

Thanks, Yes, those rudes have a way of hanging around, at this point, My wife thinks they are mating and having babies!

:eek:

:lol:
 
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bonz_d

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Thanks, Yes, those rudes have a way of hanging around, at this point, My wife thinks they are mating and having babies!

:eek:

:lol:

I seem to be having the same problem with the 2 cylinder 50hp family. I now have 3 of them.
 

Willyclay

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I have corresponded with Mirrocraft and they have identified it as a Sportsman model that was rated at 45 hp, great I have 2 Evinrude 40hp big twins, so I want to put one of those on it.

Did you tell Mirrocraft the transom had been altered/lowered? Even if the plywood core is solid, depending on the age of the boat the original max HP rating was based on the original design which probably was a 20inch high transom AND remote steering. Refer to the USCG CFR 2004/Title 33, Sub-Part D, Section 183.53 below.

http://www.gpo.gov/fdsys/pkg/CFR-200...-sec183-53.pdf

Go through the calculations yourself with the exact measurements of your boat and see where that puts you before making a final decision on how you want to proceed. Be safe!
 
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MTboatguy

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Did you tell Mirrocraft the transom had been altered/lowered? Even if the plywood core is solid, depending on the age of the boat the original max HP rating was based on the original design which probably was a 20inch high transom AND remote steering. Refer to the USCG CFR 2004/Title 33, Sub-Part D, Section 183.53 below.

http://www.gpo.gov/fdsys/pkg/CFR-200...-sec183-53.pdf

Go through the calculations yourself with the exact measurements of your boat and see where that puts you before making a final decision on how you want to proceed. Be safe!

No worries, Wily, I sure will, I don't want to take any chances, this is a project boat, I have another that we use for fishing, so I will make sure things are safe on this one.

Thanks again for the reference.
 

Woodonglass

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WC, is correct, however, if the Old Rude's are Clamp on Motors and NOT Bolt On motors (as I suspect they are) AND as long as the clamp on bases do not extend past the surface of the wood then I'd expect the wood transom, as it's currently configured with the Knee Braces, to stand up sufficiently to the weight. A raised motor "Bounce" test would quickly tell you if this is the case. Any flex would quickly let you know that reinforcement would be required. The 3/4" plywood Back Plate would then be the preferred fix IMHO.;) BUT...I'm NOT a Tinner and also just an Old Dumb Okie sooo...Don't forget that!!!!:D:culpability:
 

gm280

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After looking (again) at the pictures, seem the person that cut the transom down may have done so with one eye closed. Or a beaver did it thinking it was a tree he needed. Because the both sides are not even close to being uniformed. Maybe the person was in a hurry and didn't remember how the other side was cut... Oh well seem you have it all figured out. Just be safe. NO boat is worth anybody's life. JMHO!
 

MTboatguy

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gm, who ever did the cutting, must of done it on a Friday night after he had been hanging out at the bar to long! I think what I am going to do is laminate another piece of plywood to the correct dimensions, but I will embed some steel bars in it to add strength to it, part of what will add strength to it is putting a top cap on it.
 

MTboatguy

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Willyclay,

I did want to mention when I corresponded with Mirrocraft we did not talk about how the transom had been cut, I was just trying to identify the model that I had because I don't have a title on this boat yet, but have been issued some paper work from Mirrocraft so that a new title can be issued by the state once they do a search to make sure it is not stolen(Its Not) I have been able to track down all of the people that owned it since new as it was sold at one of the local boat dealers in 1968.

I did go back out and did some tests on the transom, and it, even being cut down is still pretty darn stout, those knee braces are bolted with stainless steel bolts through the transom, there is 4 each on the two outside knee braces and 2 on the center knee brace. I did a bounce test on it with the 9.9 merc that is hanging on it right now and being an older merc it is a heavy motor, not quite as heavy as the 40 horse rude, but close enough to give me an idea if there is any flex when bouncing the motor, and there is none.

The next thing I need to figure out is the best way to bend the aluminum C channel that I bought, I am thinking that I can heat it where is is going to be radiused at the ends, that is after I clean up the cuts that last guy did.

Anyway, thanks for the help guys.
 

Watermann

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Willyclay,

The next thing I need to figure out is the best way to bend the aluminum C channel that I bought, I am thinking that I can heat it where is is going to be radiused at the ends, that is after I clean up the cuts that last guy did.

Anyway, thanks for the help guys.

I heated my transom cap with a torch to bend it to shape. When the material gets to the right temp it's easy to tell as it becomes very easy to bend.

IMAG0312.jpg
 

MTboatguy

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Watermann, I just looked through your thread on the Chieftain Restore, great job, beautiful boat, I was wondering, where did you take that video, it reminds of some of the areas that I used to hang out on in eastern WA when I was growing up. It actually reminds me of the Columbia river, upstream of the dam they found the cracks in the spillway last year.
 

Watermann

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Thanks, yeap the Columbia River but quite a ways upstream from Wanapum Dam around 150 miles north behind Chief Joseph Dam. The terrain is very similar though.
 
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