New transom pod install

the454assassian

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Jan 30, 2011
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So I got a new transom pod rated to hold my motor since the last one wasn't and we had a failure. Since the new pod is alot stronger than the old one and larger. Should I move it back some the the engine is further away from the boat? And my next issue is the motor mounting, since the bottom of this new pod is lower than the other one. Should I try to put the cavation plate even with the bottom of the pod or go higher with the water line level?
 

ahicks

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I'm assuming talk about an engine pod in the pontoon section of the forum will be talk about a pontoon boat... When talking about moving the motor forward or backward, you need to keep balance and weight distribution in mind. Not as big a deal with a 25hp, but when you get up into the 75-90hp engines, you can be talking about significant changes in how high the boat floats. If we're talking about a larger engine on an older boat with smaller diameter toons, I would NOT move the engine back. There's no upside, and you're just going to cause the boat to float lower in the back.
 

the454assassian

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Jan 30, 2011
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I'm assuming talk about an engine pod in the pontoon section of the forum will be talk about a pontoon boat... When talking about moving the motor forward or backward, you need to keep balance and weight distribution in mind. Not as big a deal with a 25hp, but when you get up into the 75-90hp engines, you can be talking about significant changes in how high the boat floats. If we're talking about a larger engine on an older boat with smaller diameter toons, I would NOT move the engine back. There's no upside, and you're just going to cause the boat to float lower in the back.

Thanks for the insight. I will not extend it out further. What is your opinion on the height issue since the the pod is about 3 inches deeper than the old one?
 

ahicks

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It is what it is. I wouldn't loose any sleep over it. I would not mount the cavitation plate any higher than the bottom of the pod for sure. That's almost guaranteed to screw up the water flow to the prop. After that, there's a ton of variables. Size of the toons, the size/weight of the engine, how the toons are handling the weight (ride height?) I would set the cavitation plate even with the bottom of the pod and launch it to see what's going on. If everything looks good, a drive would be next, looking for any issues that might be present. Last, deal with the issues, and go enjoy the boat.....
 

5150abf

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A lot of questions still, "we got a transom pod rated to hold my motor, the last one wasn't and we had a failure"
please elaborate, how big is the engine and what exactly failed?

Where did you get the new motor pod and how do you know it is rated to hold your engine?

My next concern is you got the correct motor pod but the cross members and deck it mounts to are also part of the system and figured into the rating so you can't just take a pod rated for 50 horsepower and replace it with one for a 300hp and be good, the structure of the boat is a huge factor in rating for hp.

The cross members on the boat are designed to hold a certain horsepower, larger power more and thicker crossmembers, smaller power smaller and lighter cross members.

My concern is you put this heavy duty motor pod and big engine on a structure to small to hold it and you are setting up for a different failure.

What was the original boat rated for and what do you have on it now?

As a qualifier I have built pontoons for 32 years.
 

the454assassian

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Jan 30, 2011
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A lot of questions still, "we got a transom pod rated to hold my motor, the last one wasn't and we had a failure"
please elaborate, how big is the engine and what exactly failed?

Where did you get the new motor pod and how do you know it is rated to hold your engine?

My next concern is you got the correct motor pod but the cross members and deck it mounts to are also part of the system and figured into the rating so you can't just take a pod rated for 50 horsepower and replace it with one for a 300hp and be good, the structure of the boat is a huge factor in rating for hp.

The cross members on the boat are designed to hold a certain horsepower, larger power more and thicker crossmembers, smaller power smaller and lighter cross members.

My concern is you put this heavy duty motor pod and big engine on a structure to small to hold it and you are setting up for a different failure.

What was the original boat rated for and what do you have on it now?

As a qualifier I have built pontoons for 32 years.

Before I bought the boat someone did a motor swap. It now has a Johnson 150 fast strike from a bass boat on it. I am not sure what the factory motor was but I know the old transom pod was rated for 100hp motor.

The old transom pod failed on the welds on the backside where the motor mounts.


I got the pod from Billsboatstuff.com The new pod is rated for 200hp.

I don't recall the specs off the top of my head for the cross members ( size, thickness and spacing). But I can get that info for you tomorrow. We did add additional support anyways because I didn't like how the back of the pod had no cross members. So at the last set of cross members we ran a 2 inch square aluminum bar 1/4 inch thick across the top of the pod and butted it up against the other cross members.
 

the454assassian

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ok gents here are some pics. some of the old pod failure. some of it on the trailer. some of it floating freely. and some of it under way.
 

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the454assassian

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any tips or suggestions on how I should proceed next?
My wife says quit messing with it and putting money into an old boat. Just buy a new one.
Me being a mechanic as a career I prefer to fix instead of buying a new one. kind of ingrained into me haha.
 

ahicks

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Any tips on how to proceed would depend a lot on exactly what it is you're trying to fix? It looks like you have it mounted and have run it, how does it work? What needs fixing? Is the engine turning up rated rpm at wide open throttle? Are you running into any cavitation issues at any point? What is it that's preventing a "they lived happily ever after" ending to your story?
 

the454assassian

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When it is under way water is coming up over the motor so bad it looks like the back end is sinking. The pics were at 2k rpm. Today i am going to install some sheetmetal between the transom pod and the boat frame to prevent the splashing. It was so bad that the water was going into the air intake vents on the top of the motor cover.
 

ahicks

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Got it! I saw the motor trying to be a submarine, but it wasn't clear about what was going on to make it do that.

The pics show the motor is WAY too low in the water while underway. One or a combination of a couple of things are likely responsible. First, that's an older pontoon with small tubes. The weight of that motor is causing them to float lower than they were designed to float. Second, the engine pod design isn't carrying the motor high enough in relation to the tubes. The sides of the engine pod, which extend up to the flooring cross members, is too tall. The fact you already have the engine mounted on the transom with the cavitation plate even with the bottom of the pod means there is no room to lift the engine any higher. If you try, the bottom of the pod is going to screw up the water flow to the prop, causing further issues.

I think mom is right. A different boat (with larger tubes that can handle a motor that size), or a smaller motor, are your better directions.

Last, there's a good reason you don't see 6 cylinder engines on a regular pontoon often (nearly always on a tri toon). It's their weight. A 4 cylinder is about max. Something under 350 lbs or so is about all you can get away with on the newer/bigger tubes you see used in production on the newer boats. That kind of weight, as proven by your pics, will nearly always overwhelm an older boat with smaller tubes.
 
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the454assassian

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Shhhhh dont say that. I might never live that "I told you so" down.
Right now my options seem to be get a different transom pod that will raise the height of the motor.
Or get larger logs.
I am personally leaning to the larger logs because the motor is heavier than what was stock and the new pod is stronger but it seems to be designed for larger logs with that can carry more weight.

Plus i dont like having plastic pontoon logs
 

ahicks

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Well, if it's a "make it work" proposition, another plan might be adding a center 'toon with a built in transom. A slightly larger full length center toon wouldn't hurt a thing (25" maybe?), and it it were purchased with lift strakes, it may provide you with a pretty nice boat (under the floor anyway).

The larger center toon will let the boat bank in the correct direction (toward the inside of the turn!). Obviously, it would raise the back of the boat up as well.

Note that tri toons need a special trailer and lifts to accommodate the center toon....
Big motors on a conventional 'toon have an unnerving habit of leaning to the outside of a turn at speed....
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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What do you think about a hydrofoil? Maybe it could give me some lift on the back end

since we are talking band-aid attempts

may as well hook a hot-air balloon to the motor first to lift it up to the point where the pontoon/motor combo would get enough speed for the hydrofoil to provide enough lift
 

ahicks

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I'm with Scott, but maybe because I'm old school. I don't think a hydrofoil (even more weight) would be a very practical solution.
 
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