Time to redo the transom and add some flotation pods PICS!!!

[orion_134]

After years of being pissed off at my 1648 and the previous owner's shenanigan repairs, it's time to redo it. Currently the rear of the hull drafts over 6" with no one in it leaving very little transom freeboard once loaded. To top it off, they put a ghetto addition to the top of the transom to mount the Merc higher and it is rather poorly done. Icing on the cake is that the transom board is actually peeling/breaking the transom braces that go to the floor of the boat. It looks like it's a few bumps on a dirt road away from dragging my Merc by the cables down the road.

So, the plan.

To fix the freeboard/draft issue I'm going to weld some flotation pods like ranchero50 did to his jetboat. I'm buying a Miller Spoolmate attachment for the MIG and going to town on it. I plan to mount the bilge in the pod, and drill drain holes between the boat and pods so that if the pods do leak or whatnot, the bilge is at the rear and the pods won't fill with water. The drain holes will be standard plug size so that if they do get swamped, I can plug them if needed. Aye or nay?

The transom dips down lower than the side of the boat, but the ghetto rig to lift the motor picks it back up level with the sides, so my plan is to make the transom the same height as the sides of the boat. I was going to take out all rivets and bolts going through the back of the boat, and add a sheet of aluminum to the transom to essentially reskin the back of the boat (before adding pods, obviously). Then redo any rivets or bolts going through. I figured I'd do a perimeter weld but also cut a couple holes in the skin so I can do some plug welds to keep the center of the skin attached to the original transom. I would then put a C-channel or L-shaped angle aluminum across the top as a top brace for the edge of the transom, and then add another 6"-ish sheet of aluminum under it on the inside of the boat as a clamping/mounting surface for the motor once the transom board is put in the space between. Then I was going to make new angle brackets/braces to fix the transom to the floor.

Sound like a plan?

 

[orion_134]

What can I do to get rid of the wood in the transom, can I reinforce it with aluminum instead?

 

[Ranchero50]

Depending on what you find once you tear into it you may be better off making a new transom, reinforced with aluminum square tubing. I guess you'll need an allowance to clean any corrosion (washdown) for it too.

Thinking outloud, 2" boxtube for a transom cap and reinforcements, skin it with .100" and add corner braces. Then rerig the hull and see how it floats before deciding on the pods.

Jamie

 

[SVOMike86]

As far as other options than wood in a transom, aluminum like Jamie suggests is probably the easiest, but Huntinfool has a link in his sig for pouring a glass transom. Doesn't look too hard, and I would kill for one of those.

 

[orion_134]

I say that the rear sits too low need on the rib along the water line being much lower in the rear, not by how much transom freeboard I have, so I still think pods are a go.

 

[lckstckn2smknbrls]

I wouldn't put a hole from the boat into the pod.

 

[orion_134]

I wouldn't put a hole from the boat into the pod.

Care to justify your position?

 

[lckstckn2smknbrls]

You don't want any water getting into them It defeats the purpose.

 

[richg99]

Just to add to this excellent comment "You don't want any water getting into them It defeats the purpose."....

Once water got in them..how would you EVER get it out? Seal them. Good advice, IMHO Rich

 

[SVOMike86]

I plan to mount the bilge in the pod, and drill drain holes between the boat and pods so that if the pods do leak or whatnot, the bilge is at the rear and the pods won't fill with water. The drain holes will be standard plug size so that if they do get swamped, I can plug them if needed. Aye or nay?
Sound like a plan?

Bilge pump in the pod. Sounds like a plan to me. Just make sure you keep an access hatch on them so you can get to it if it malfunctions...

 

[Ranchero50]

I did two 3/8" holes between the pod and regular hull. When I poked a hole in mine I was able to shove a couple plastic worms in the drains from where the trim tab was ripped free. I also had a 3" tear where the transom ripped from the bottom packed with worms. It didn't leak bad enough to worry about after some riverside repairs.

A sealed pod to me is a bad idea. I want it to breath so condensation or leaks don't mold or corrode. I also want to know if it's leaking. The drain holes are small enough that if you do have a catastrophic failure you won't flood the hull faster than the bilge pump can drain it.

After my whack I had enough time to get it to shore and jacked up with rocks to drain the hull before applying the worms.
Jamie

 

[Anonymous]

The pods on my Alweld are factory, and sealed ...
Never really thought about having a need to have them drain.

 

[lckstckn2smknbrls]

Just to add to this excellent comment "You don't want any water getting into them It defeats the purpose."....

Once water got in them..how would you EVER get it out? Seal them. Good advice, IMHO Rich

I have seen some pods with a screw in drain plug built into them, but not a hole from the boat into the pod. A removable water tight cover is a good idea.

 

[SVOMike86]

A removable water tight cover is a good idea.

Tupperware?

 

[lckstckn2smknbrls]

A removable water tight cover is a good idea.

Tupperware?

Most kayaks have at least one water tight compartment with cover on them, use the same cover assy.

 

[redrunner]

I did about what you are taking about last summer. I replaced the wood, made a new transom cover plate out of aluminum 1/8 thick sheet stock. Took another 1/8 sheet on the outside as well. Had pods made and welded to the outside plate. Had plug holes put in. Standard boat plug size. Then had it all welded to the boat. I raised the transom to handle a long shaft motor. I had the bracing from the sides to the transom replaced because the old transom was lower. Then the knee braces in the back were strengthened.

I love the mod. Best thing I did to the old boat. I put on a fresh coat of paint when it was all done and you can't tell it was not factory done.

 

[orion_134]

So I priced the Miller Spool Mate 100, wire, tips, and metal for the project...Break Out Another Thousand.

I am also planning on buying the CMC PT-35 so that I can trim the motor to get some more speed, but primarily so that I can save it from oyster bars and shoal beds in this area. $500 is way cheaper than than the $900 that Mercury wants just for the hydraulic ram.

So my predicament is this: I know that adjusting trim is important to optimize the combo, but I also know that having height adjustability is also important especially when in the fine-tune phase. But, how important is it really and is it worth it?

The CMC PT-35 has a set-back of about 5.5", and if I make a DIY manual jack plate from angle aluminum, I'm looking at another 3-4" of setback. Is 8.5"-9.5" of set-back acceptable? Keep in mind this engine weighs approximately 175 lbs.

The further back the engine sits, the higher the cavitation plate can sit, plus with my addition of flotation pods...I think I'll be guessing at the height of the cavitation plate unless I have an adjustable jack plate. See my predicament?

What do y'all think? Just make a DIY jack plate and bolt the PT-35 to it?

 

[richg99]

In the flats around South Texas...two inches of SETBACK normally would allow one inch of "rise".

I've owned the CMC-35 as well as a couple of standard hydraulic jackplates. No question, the hydraulic vertical jack plate is the best arrangement to protect your prop in oyster reef areas. It allows the best bet for getting top speed and hole shot, too.

Having a hydraulic tilt arrangement, like the CMC -35, is good and worked well for me, but automatic vertical rise adjustment is even better, IMHO.

Having both vertical and tilt is, obviously, what everyone would want.

8 or 9 inches of setback seems like a lot of strain to put on your newly built transom.

Would it be possible to build your new transom and allow for a couple of adjustment holes, instead of adding another setback with an adjustable riser? Perhaps welding double thick plates in line with your engine mounting would allow for a couple of tries to get the height right.

The motor mounting plate may have a number of height adjustment holes, too.

A number of my motors have been professionally mounted one or two inches higher than the motor clamp's base. Those motors were, of course, bolted through with four bolts. The gap between the mounting base and the top of the transom didn't even have a filler in it, as it bears no weight.

Obviously, getting the exact correct rise would require mounting and remounting the motor a couple of times.

If that system didn't work, you could always add your additional manual jackplate.

regards, Rich

 

[orion_134]

In the flats around South Texas...two inches of height normally would allow one inch of "rise".

I don't know what that means.

So with the motor mounted to the transom, I'm looking for the cavitation plate to be level to about .5" above the bottom of the boat. Is there a rule of thumb that will give me a good starting point for my initial position considering I will have x" of setback?

 

[richg99]

re...Two inches setback means one inch rise ....

(SORRY THAT I CONFUSED YOU WITH MY POST ABOVE,,,,,USING HEIGHT INSTEAD OF SETBACK)

Caution, this formula is seen differently by various groups and areas of the country. Who really knows what is right.???..but...my mechanic of the last 15 years, who works on flats ( very shallow water) boats all of the time, uses it. That is good enough for me.

If your anti-cav plate was exactly even with the bottom of the boat....and you wanted to raise the motor ( and, of course, its anti-cav plate) say, three inches...you would build for 6 inches of setback. i.e. 6 inches of setback equals 3 inches of rise. Same as .. two inches of setback equals one inch of rise.

If you want little or no extra height...you would have little or no set-back. However, if you are running in skinny water...then raising the engine can be a good thing, IMHO.

Obviously, you don't want to raise it too far, and starve the motor for water. If you picture a hypothetical transom...flat on the bottom...running through the water, you should see that the water shoots UP as it clears the bottom of the boat. That "shooting up" water is what you use to cool your engine.

Because you are looking at the CMC-35 that device is going to add TILT...and, just because it has to be a certain thickness, adds setback. The built-in set-back (thickness) demands that you raise the engine a certain mount, I'd say.

Before you do anything like this, though..you probably want to visit some flats boat sites. Bob's Machine Shop in Florida is a major supplier of jack plates. I would imagine that he has some fitting out and measuring information for potential buyers. Try his site here..
https://www.bobsmachine.com/FAQ.cfm


Lots of comments and suggestions on the net....first two are from Bob's site...the last one from Bass-pro. Also, do a search for "flats boats & jackplates" and you should find a ton of other people who have put jackplates on.
regards, Rich
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From Bob's

Q: How do I determine the correct set back for my boat?
A: For motors 40 horsepower to 115 we recommend the 4 inch ultra light. Our 6 inch jack plate is a good choice for most flats and bay boats. Our 4 inch heavy duty is good for boats with heavy 4 strokes, the Verado or for applications where the motor should be close to the transom. 8 and 10 inch jack plates are a good choice for bass boats or for boats that require more bow lift. It is always a good idea to ask your boat’s manufacturer which set back they recommend for your model boat.

Q: What are the benefits of installing a jack plate?
A: Installing a jack plate will help to improve your speed and performance, reduce your fuel consumption and allow you access to shallower water.

From BassPro's site...

Customer Questions & Answers for
CMC Manual Transom Jack Plate

(...not the CMC 35)

High-strength extruded aluminum mounting bracket Allows 5" of slot adjustment at the motor mounting bracket Allows 1-1/2" slot adjustment at the transom bracket Includes hardware - No drilling or modifying This high strength 6061 extruded aluminum alloy mounting bracket lets you easily raise or lower your motor with a 1-1/8" wrench. Adjustment can be made at the top or the bottom. Allows 5" of slot adjustment at the motor mounting bracket and 1-1/2" slot adjustment at the transom bracket. Position it at the precise height for optimum motor performance, increased top-end speed, better prop clearance, lower engine RPM, reduced lower unit drag, and improved fuel consumption at cruising speeds. The bracket also sets your motor back 5-1/2" to let it run in cleaner water for peak efficiency. It mounts easily with included hardware - no drilling or modifying. For V-6 and smaller engines up to 300hp.