How to raise transom..

[RichBKK]

I recently rebuilt a transom on a 1980 MirroCraft "Deep Fisherman".. It was formerly a 15" transom with a "Mini Jacker" plate installed to accomodate a 20" shaft Evinrude 30hp ETEC.. I built and installed the new transom, making it 20 1/2" high.. Anyway, re-mounted the engine and the cavitation plate is 2" below the keel.. ("What tha heck..??")..

I do not want to re-mount the "Mini Jacker" plate due to the increased "fulcrum" and extra weight.. Anyone have any suggestions on raising this engine without having to pull the new transom, throwing it in the trash and starting over..??

Thanks for any and all help..

Richard

 

[jigngrub]

Re: How to raise transom..

Not me... pull the transom and build a new one if you're not going to use a jack plate.

Building the new tansom a little too tall and doing a dry fit with the motor to see exactly how much you need to trim it down will be better than building it too short again.

 

[ondarvr]

Re: How to raise transom..

Is it 2" too low when mounted in the highest position possible, or when the motor is dropped right down on top of the transom?

 

[Teamster]

Re: How to raise transom..

I think I would just build it the way it was and use the "mini jacker",...

 

[RichBKK]

Re: How to raise transom..

I thank all 3 of you for your replies and help with this heart breaker transom.. I'll try and answer all of your questions and give a bit of my own experience also.. Here goes..


1) Building the new tansom a little too tall and doing a dry fit with the motor to see exactly how much you need to trim it down will be better than building it too short again.

Reply: This sounds like the most difficult, expensive and time consuming way to do it but-----also the "most correct for me and boat.. I began building the new transom Oct. 20th.. Took 10 days to complete.. Had to cut a cardboard template, then used 2 pieces of 11 ply birch, hardwood plywood.. After getting the fit perfect, then epoxied them together with "610 Epoxy" and used 46 drywall screws screwed in from both sides.. Let dry for 2 days, then palm sanded her perfect, then "Marine-Tex'd" all screw heads, sanding again a day later.. Then followed the West System's "105 Epoxy Resin" and 206 Epoxy Slow Curing Hardener".. A day later, palm sanded and another coat, etc. for a total of 3 coats overall and 4 coats on the edges.. Again, palm sanding after the final coat.. She came out beautiful..

Then went to a metal fabrication shop and had them cut 2, 42" wide x 9 1/2" high, 1/8th" sheets of aluminum to fit inside transom braces (against the wood transom) and on the outside of boat.. They also made an "end cap" to fit over transom "top" and the 2 mounted sheets of aluminum..

Lastly, she was fitted and drilled thru and bolted with stainless steel bolts, self locking nuts and washers.. 5200 glue was used in the drilled holes before assembling.. Total cost was $228 and change.. The aluminum plates and end cap were $118.00 of that..

Finally-----No, I did not "glue" the transom into the boat, nor glue the alluminum plates or end cap to the transom or boat.. (just in case of a "huge disaster", such as this..)


2) Is it 2" too low when mounted in the highest position possible, or when the motor is dropped right down on top of the transom?

Reply: 2" too low when dropped down on top of the 1/8th" thick "end cap" that rests on top of transom.. (the engine itself is set on the 2nd hole from bottom of the engine bracket.. Slight porpoising when at WOT..)


3) I think I would just build it the way it was and use the "mini jacker",...

Reply: The "Mini Jacker" was on it when I bought it (the boat had a 15" cut out transom and even with the mini jacker, cavitation plate was 3" too low).. When the vessel was sitting dockside, her bow was in the air.. When idling or trolling with me aboard (I'm 200lbs), it was ridiculous.. Even when planed off, even at various "pin settings" on her engine mount, I was "rubber-necking" to even see over the bow.. The extra 25lbs and increased "fulcrum" not only kept her bow in the air limiting visibility and handling but, also bothered my shoulder and-----just looked ridiculous.. ("What kind of a jerry-rig and scab job is this..??!!")..

I have seen a special "plate" that addresses problems such as this on the internet but, can't find it after 2 nights of searching.. It had like 2, 1" aluminum (or stainless steel) square tubing that were welded on top of each other.. Then front and back "sheets" of aluminum (or S.S.) that the welded tubes fit inside (the sheets bent over the tubes) and the sheets then fit over the top of the transom and were bolted thru down lower on the transom.. Effectively raising the engine 2".. Wasn't that expensive either, like 80 to 120 dollars..

Should I just "wedge" a 1" square tube of aluminum under the engine bracket and really count on / trust that the 2 bolts that will bolt the engine thru the transom will be enough to secure the engine..??

What's really hard to believe is when I measure the engine bracket (from where it sits directly on top of the transom) to the top of the cavitation plate, it measures 22".. Yet, Evinrude says it's a 20" shaft.. I don't get it..

Again, thank you for all of your help and advice..

Richard

 

[Woodonglass]

Re: How to raise transom..

With your description, there are a lot of issues. One, using Birch Interior Grade Plywood is not a good practice. It is not rated for exterior use and the glue will not hold up in a Marine Environment. You should use Ext. Grade Plywood. Arauco is a really good one to use. Two...You ALWAYS glue the transom to the exterior skin of the Boat AND using fiberglass cloth tab it into the Sides and Bottom of the hull at least 10" or so. Three...A properly built and installed transom does not require addition aluminum plating. I suppose you could add them as a cosmetic effect and for the transom clamps but they really won't do much concerning the strength of the transom. They could be mistaken as someones attempt to repair a failing transom. If you use the Proper materials and techniques building a taller transom to accomodate your motor should be fairly straight forward and easy to do. Search the forum fot transom repair and you'll find plenty of pics and details on how to do this the right way.

 

[jigngrub]

Re: How to raise transom..

Two...You ALWAYS glue the transom to the exterior skin of the Boat AND using fiberglass cloth tab it into the Sides and Bottom of the hull at least 10" or so. Three...A properly built and installed transom does not require addition aluminum plating. .

I believe his Mirrocraft is an aluminum boat Woody.

 

[jasoutside]

Re: How to raise transom..

I believe his Mirrocraft is an aluminum boat Woody.

Ayup!

Working with fiberglass is just so itchy:victorious:

 

[Woodonglass]

Re: How to raise transom..

Oh Carp, I KNEW I had to much on New Years!!!! Now Everybody knows I'm an...

 

[jasoutside]

Re: How to raise transom..

What's really hard to believe is when I measure the engine bracket (from where it sits directly on top of the transom) to the top of the cavitation plate, it measures 22".. Yet, Evinrude says it's a 20" shaft.. I don't get it..

For what it's worth, I've measured my Evinrude 15 hp LS a dozen times thinking I did something wrong. Nope, every time I come up with 22".

 

[ondarvr]

Re: How to raise transom..

You can raise the motor up the two inches without much work.
If it has clamps instead of bolts at the top just sandwich a square tube between to pieces of aluminum and clamp to that, run the lower bolts through the aluminum and it will all be tied together.
If it has bolts both top and bottom, just raise it to the proper height and bolt it in place.

 

[jigngrub]

Re: How to raise transom..

You can raise the motor up the two inches without much work.
If it has clamps instead of bolts at the top just sandwich a square tube between to pieces of aluminum and clamp to that, run the lower bolts through the aluminum and it will all be tied together.
If it has bolts both top and bottom, just raise it to the proper height and bolt it in place.

Not something I'd do on my boat... I wouldn't trust it, but that's probably just me.

 

[RichBKK]

Re: How to raise transom..

But wait, "WoodonGlass".. Hold on.. I bought the 11ply Birch hardwood plywood at Lowes (after checking out Home Depot and a simalar place that carried Marine Plywood..).. I was told by the salesman at Lowes (and the manager) that the plywood I was looking at was "glued" together with exterior glue.. (I had told them where and how I was going to be using the wood, for my transom)..

The 3/4", 11 ply Birch hardwood, 4'x8' sheet was "flawless" and cost $37.00 ($10.00 off cause it was on sale).. The Marine ply was either 5 or 7 ply, most certainly wasn't a "visual or quality piece of plywood", in my opinion, very heavy, flexible too and cost $87.00..

2 pieces of the 3/4" were epoxied together with West System's 610 Epoxy, drywall screws from both sides (heads covered with Marine-Tex), 3 solid coats of West System's Epoxy 105 with 205 hardener, 4 coats on all the edges (palm sanded between coats).. Any holes drilled thru were meticulously "filled" with 3M's 5200, then "pushed thru" and filled by stainless hardware..

Moisture intrusion into the transon is really not an option.. I don't see how or where water could possibly enter and destroy it anytime soon.. It's sealed.. True, nothing lasts forever but, neither did the 1980 "Marine Ply" transom that was installed by the factory----that was long gone when I bought it.. (a 2"x6", pressure treated board was in it's place.. with mini jacker bolted thru that..)

And, glue the exterior skin to the transom board..?? How tha heck would you possibly pull the transom out of the boat to replace it, if it was glued with anything other than Elmer's Glue..??!! Just imagine if I'd glued this (or even if factory boats were) with 5200.. How would I pull this thing apart..?? Just Sawzall the entire stern out..??!!

I'm not sure what 1980 MirroCraft, 14' "Deep Fisherman" look like where your at but, I've never seen one (or any aluminum boat for that matter) with any "fiberglassed tabs to the sides or bottom of the hull"..

But, thanks for your input..!!

 

[RichBKK]

Re: How to raise transom..

You can raise the motor up the two inches without much work.
If it has clamps instead of bolts at the top just sandwich a square tube between to pieces of aluminum and clamp to that, run the lower bolts through the aluminum and it will all be tied together.
If it has bolts both top and bottom, just raise it to the proper height and bolt it in place.

I took the boat with engine mounted to a machine shop.. Basically, what you've said, they were going to do---plus weld the whole thing together, then bolt it thru my aluminum plates and transom.. All for the "cheap price" of $300.00..!!

I spoke to a buddy on the phone tonight and told him of my predicament.. He said to maybe try raising the engine just an inch, sliding a 1"x1 1/2" square aluminum tube under the engine bracket, to raise her 1".. The screw down clamps would be worthless but then bolt thru the transom (engine bracket bolt holes) and use a 6" or 8" wide x 3" or 4" high piece of Stainless Steel as a giant washer (that both engine bracket bolts would go thru, besides the aluminum plates on the interior of the transom and exterior of the boat)..

Very much like your were suggesting, OnDarVr.. My friend also mentioned that the engine would still be 1" too low but----on the bright side----it's still 1" higher than what I have now.. And the bolt-thru's would still be grabbing some "meat" of the transom..

 

[jigngrub]

Re: How to raise transom..

They lied to you about the glue in the plywood, or more likely they didn't know what they were talking about. Go to the Lowes online store and look up the Birch plywood and the click on the specifications tab and you'll see the exposure rating is interior.

True, it'll probably last for years with the epoxy coating and all penetrations are sealed thoroughly... but as soon as moisture finds a way into it, it will deteriorate rapidly.

The marine plywood that was installed at the factory wasn't sealed before or after installation, and there no telling when it started to deteriorate before you got the boat. As you saw, marine plywood will rot just like any other untreated or unsealed plywood.

The glue in the exterior grade plywood is the same glue they use in the marine plywood. The marine plywood is more expensive because it has more plies, no knots or patches in any of the veneers, and isn't supposed to have any voids between the inside plies.

 

[RichBKK]

Re: How to raise transom..

For what it's worth, I've measured my Evinrude 15 hp LS a dozen times thinking I did something wrong. Nope, every time I come up with 22".

Hi Jasoutside,

Thank you for reassuring me that I'm not alone in this whole, "I swear this yardstick says 22"----you try measuring it..!!" thing.. I was starting to think that maybe I'd bought some weird, freaky, factory screw-up..

So what was your Evinrude mounted on and did you have to "customize / rebuild" your transom to accomodate the extra 2"..?? If so, what did you do to correct it..??

 

[Woodonglass]

Re: How to raise transom..

I guess you didn't read post #9. Everything I said was for a Fiberglass boat, NOT a Tinner, EXCEPT for the plywood. That was true for any boat. The Birch Plywood, I guarantee is NOT exterior glue. As long as you ALWAYS predrill and coat the holes and any and all mechanical fasteners with Epoxy it should still last many years. Epoxy has NO UV protection so for even longer life, I'd recommend either coating it with a couple of coats of Marine Spar varnish with UV protectants or Rustoleum Professional Oil Based Paint.

 

[ondarvr]

Re: How to raise transom..

Not something I'd do on my boat... I wouldn't trust it, but that's probably just me.

It's very common, around here, many tinnies are converted from prop to jet and it needs to be raised 5" for the jet to work correctly. Some 5" risers are welded and other are sandwiched, for something in the 30HP range sandwiching works fine. At 2" it's no issue at all.

A two inch riser can be fabricated for about $30.00 and a couple hours of work.

 

[jigngrub]

Re: How to raise transom..

On second thought, a piece of 1/8" thick 1-1/2" aluminum square tube lagged down to the top of the transom with 1/4" diameter 3" long stainless steel sheet metal screws shoud be a pretty stout fix and get you withing 1/2" of the optimum height for your motor which should be close enough. I believe the tolerance is plus or minus 1" for the cavitation plate and the bottom of the hull anyway.

The 1-1/2" square tube will fit your transom nicely and leave enough of the 3" screw to give a firm bite into the transom for a secure installation.

Remember to seal everything up real good with 3M 5200, you don't want water getting to that wood in your transom.

 

[55evinrude]

Re: How to raise transom..

Just bolt it to the transom with a 2" space between the transom and the bracket. Ive added a pic to help me explain (yes i know its not the same motor but who cares). just my 2 cents

Nathan