Boat building question

[Toon Merc 140]

Ok maybe this isn't in the right place but I have a question that I have been wondering about for some time! To start off with I have a 24' Harris Float Bote pontoon with a 140 Mercruiser I/O! What my question is why on my boat and how many others I have seen do they put the motor clear in the back when to my small country boy brain if it was put more in the center of the boat it would help level everything out and then the boat would plane out easier! In my boat everybody seems to want to hang out in the back and then it for sure has problems planing out good! Ok then the last part of my idea crazy as it may be but I had this brainstorm to build a pontoon boat and make the pontoons just wide enough to fit either a 4 cylinder or a 6 cylinder in each pontoon! Ok yes I know crazy thinking!!!!

 

[H20Rat]

Re: Boat building question

I/O pontoons are a bastardized red headed step child of the boating world. Although interesting, they are a very, very small market. Simply put, the cost to engineer a system doesn't justify the end result. Also, most people don't want a big doghouse in the middle of their floor space on a pontoon, its much easier to put it at the end.

And as far as putting them in the pontoon, that just sounds like a maintenance nightmare! Also, an engine inside a metal tube is going to be instantly loud (and not a good way), the tubes will function like speakers.

 

[spoilsofwar]

Re: Boat building question

Engine in the center of the boat has its advantages, but it also requires a long jackshaft between the engine and the drive in an I/O configuration. Stingray actually built a boat using this concept, although it was a center console I/O, not a pontoon boat (the 200 MS). I can't think of any other boats made this like, but I'm sure some exist.

smokingcrater is right, though; I/O pontoons are a tiny segment of the market, and its just cheaper and more space efficient to put the motor in the back.

 

[skyking897]

Re: Boat building question

You need to check out a thread in the Completed Projects by TurboM700, he built a pontoon and installed a 140 Mercruiser I/O.

 

[TurboM700]

Re: Boat building question

I/O pontoons are a bastardized red headed step child of the boating world. Although interesting, they are a very, very small market. Simply put, the cost to engineer a system doesn't justify the end result. Also, most people don't want a big doghouse in the middle of their floor space on a pontoon, its much easier to put it at the end.

And as far as putting them in the pontoon, that just sounds like a maintenance nightmare! Also, an engine inside a metal tube is going to be instantly loud (and not a good way), the tubes will function like speakers.

You might want to look into the higher end of pontoon boats many of them come with I/O in the 500+hp range.

O yea I wouldnt call an I/O in pontoon a bastardized red headed step child. My boat runs right by side with similar boats in the 140hp range and I can idle down and not even hear my motor running and I have a small dog house on the back of the boat that stands 6" tall.

You need to check out a thread in the Completed Projects by TurboM700, he built a pontoon and installed a 140 Mercruiser I/O.

Thanks for the kinds words.

Here is my build.
http://forums.iboats.com/completed-boat-projects/pontoon-conversion-inboard-outboard-573089.html

I will say if I did it all over again it would get a mercruiser 260hp motor (chevy 350) it still might someday but for know I'm just going to enjoy what I have.

If you have any questions ask away.

Mike

 

[Toon Merc 140]

Re: Boat building question

Thanks to all who have replied! Turbo I was looking at your thread yesterday very interesting and nice boat! I like my boat and just like some other people I like power and I've thought of putting a v6 in it but havn't done it yet but somebody told me that they have hooked up v6 motors to a 140 outboard is this something that is feasible? One other question and i should get some pics of it but my boat seems like the outdrive is not far enough in the water like when i try to go to fast with 6 people on it it seems like the prop is getting air! Any suggestions right off? I will have to get some pics posted and see what you all think!

 

[TurboM700]

Re: Boat building question

If you have a 4cyl now your pretty much stuck with it unless you want to start changing motor mount locations. An V style motor the motor mounts are on the side of the motor not front like a inline. You could go with an older inline 6cyl but there only 165hp.

If you have the ability to fabricate then you can keep the same transom but you will need to change the gear case and the motor

I have found plenty of Mercruiser V8 boats with good engine and out drives in the 1000 to 1500 dollar range. There older but still work fine. If I were togo with a bigger motor I would go this way as once parts start getting sold individual they go way up in price.

Mike

 

[H20Rat]

Re: Boat building question

You might want to look into the higher end of pontoon boats many of them come with I/O in the 500+hp range.

O yea I wouldnt call an I/O in pontoon a bastardized red headed step child. My boat runs right by side with similar boats in the 140hp range and I can idle down and not even hear my motor running and I have a small dog house on the back of the boat that stands 6" tall.

Guys are missing the point here..

So a couple things, yes, I/O based pontoons are the red headed stepchild. They are probably 1% of the pontoon market, if that. Nothing against them, I would absolutely love to own one! (saw a i/o pontoon with a 350 with captains choice exhaust on it... nice!) There are very few if any pontoons actually designed for that though, most are retrofits into an existing pontoon. (much like yours was, 700) (ok, red headed stepchild wasn't the right term, lets say black sheep!)

But the point that was missed is that the OP isn't wanting to build an I/O pontoon. He wants to build an I/O pontoon with a center mounted engine. There are many reasons NOT to do that. As someone pointed out above, there probably has been one boat in the history of boating that has used that config. (this isn't a true inboard either, like a ski boat. Easy to do in an inboard config, the gearbox is by the engine)

Biggest problem is that do you really want a LONG driveshaft spinning at 6000 rpm running half the length of your boat? Do you know the details of how to build that without having it fly apart and kill someone? The alternative is to gear it down at the engine, but now you either need a to heavily modify the outdrive, or gear it back up for the outdrive. Lots of complexity there.

 

[joed]

Re: Boat building question

1. Steering.
2. Cost.
3. functionality. Who wants a motor gas tank etc. in the middle of the nice flat deck area.

 

[TurboM700]

Re: Boat building question

Haha my reading skills must not have been upto par this morning.

Smoker is right a INBOARD pontoon inst a good idea.
Keep in mind a true inboard (not I/O) think ski boat cant turn in reverse.

If people hanging out on the rear of your boat is the issue your the captain tell them to move to the front.

 

[Toon Merc 140]

Re: Boat building question

Thanks for all the answers thats what I was wanting to know why it boat builders didnt do it! One other question my pontoon boat has some soft spots on floor is aluminum floor a stupid idea? Seems like a lifetime floor in my mind or whats the down side? Thanks Jerry

 

[skyking897]

Re: Boat building question

There's a local guy here who built a 35' pontoon and he used the checker plate aluminium for his flooring. I was on it once and right off the bat I can give you two good reasons to stick with the plywood flooring. #1 The aluminium heats up very fast in the sunlight. Think about bare feet walking on hot metal. #2 The aluminium flooring is very noisy. Bang your feet on it or drop something and it sounds like your inside a drum It has no sound deadening qualities like the plywood flooring. In his defence, he built this pontoon to move ATV's and other equipment up to hunt camp where water taxi is the only way in or out. He has tie downs built into the floor to hold cargo from shifting. Depends what you want to do with the pontoon.

 

[Toon Merc 140]

Re: Boat building question

There's a local guy here who built a 35' pontoon and he used the checker plate aluminium for his flooring. I was on it once and right off the bat I can give you two good reasons to stick with the plywood flooring. #1 The aluminium heats up very fast in the sunlight. Think about bare feet walking on hot metal. #2 The aluminium flooring is very noisy. Bang your feet on it or drop something and it sounds like your inside a drum It has no sound deadening qualities like the plywood flooring. In his defence, he built this pontoon to move ATV's and other equipment up to hunt camp where water taxi is the only way in or out. He has tie downs built into the floor to hold cargo from shifting. Depends what you want to do with the pontoon.

I was thinking I would cover it with carpet so that would help the hot part but dont know if it would cut all the sound problems that you were talking of out or not!