Moving the toons or shorting the toons

[98fatboy]

Ok here is my situation, 1994 Harris flotebote 240 classic I/O 3.0L. 15 1/2 x15 prop. My pontoons stick out about 1 1/2 feet past the foot, creating a lot of dirty water/ turbulence causing blow out/ slipping. Installed a whale tail and it has helped out tremendously but it is still blowing out/ slipping. Next step (in my guessing) would to either be moving the toons forward to make them flush with the back deck or having them cut down to make them flush with the deck. Any thoughts or ideas to help eliminate/reduce the slipping/blow out I am experiencing?

 

[ahicks]

While considering something like this, I would also keep in mind/consider the flotation needs of the rather heavy I/O power. You don't want to do anything that might cause your engine to be running too deep in the water or other issues.

Does "foot" = lower unit? Not familiar with that term.

When is it "blowing out/slipping"? Starting out, starting out while pulling a tube, turning?

Has it done this as long as you've had it or is it something that just started happening?

Have you tried different props or talked about this issue with a GOOD prop repair facility?

 

[jbcurt00]

Started this process:
http://forums.iboats.com/forum/gene...prop-for-a-24ft-pontoon-with-a-3-0-mercruiser

 

[Scott Danforth]

because your 3.0 / outdrive weighs about 3 x that of an outboard motor, the toon logs are generally pushed back farther to aid in buoyancy. you dont want to shorten the logs.

 

[98fatboy]

The reason I ask is every newer I/o I see now, the toons are flush with the rear deck. This makes me think that manufacturers have recognized the flaw and corrected it by moving the deck/transom to the rear of the toons. Just curious if anyone has done this or heard of it being done. If so what methods work best. I really like this boat and want to improve on it and make it my own. I'm not into buying new, I'm into buying old and making it better than new. With winter coming up and my boating season coming to a close , I want a new project to tackle. Ohh I asked in a different thread because the first thread was in a prop question forum.

 

[Silvertip]

Tube diameter may be much larger on newer toons allowing the different tube position.

 

[ahicks]

Re: tube diameter, yup! 'Toon manf's weren't into larger diameter pontoons back in the day. So they made them longer. Today, it's no big deal for them to set their tooling up to roll those big tubes. To my way of thinking, they're a WAY more efficient way of providing required flotation when it comes to an I/O or other heavy power.

This leaves folks with the smaller diameter tubes with pretty limited options.....

Re: your other post. I REALLY struggle with the concept that tubes protruding beyond the lower unit are able to mess with/affect the water flow into the prop. Before getting too far into this, I would suggest you seek to confirm that information elsewhere....

Meanwhile, it would be nice to have the info requested in my first post (above). I think you might find a little different solution is available.....

 

[98fatboy]

Re: tube diameter, yup! 'Toon manf's weren't into larger diameter pontoons back in the day. So they made them longer. Today, it's no big deal for them to set their tooling up to roll those big tubes. To my way of thinking, they're a WAY more efficient way of providing required flotation when it comes to an I/O or other heavy power.

This leaves folks with the smaller diameter tubes with pretty limited options.....

Re: your other post. I REALLY struggle with the concept that tubes protruding beyond the lower unit are able to mess with/affect the water flow into the prop. Before getting too far into this, I would suggest you seek to confirm that information elsewhere....

Meanwhile, it would be nice to have the info requested in my first post (above). I think you might find a little different solution is available.....

Does fine starting off, as I don't hammer down when I start off, just two people on the boat, blows out/slips @3600rpm, pulling tube @3200rpm. Choppy water I can't cruise above 3000. That's what the tach reads, with a digital tach connected directly to plug wire, tach is gradually off by 400 at the gauge, gauge reading high than digital.(that's one item on The repair list for the winter.) Max speed so far has been 20mph on a gps.

 

[ahicks]

Has it done this as long as you've had it or is it something that just started happening?

Have you tried different props or talked about this issue with a GOOD prop repair facility? If not, I think this might be your best plan. If you have a facility like this nearby, very likely well worth the drive - especially if you were to have your prop in hand when you got there.

And a new question: are you using an OEM type prop? By that, wondering about the possibility that you might be using a prop designed for higher performance applications. This is basically a tug boat, so the prop blades should look like big elephant ears. Not the raked, more modern design you see on performance boats.

 

[98fatboy]

Has it done this as long as you've had it or is it something that just started happening?

Have you tried different props or talked about this issue with a GOOD prop repair facility? If not, I think this might be your best plan. If you have a facility like this nearby, very likely well worth the drive - especially if you were to have your prop in hand when you got there.

And a new question: are you using an OEM type prop? By that, wondering about the possibility that you might be using a prop designed for higher performance applications. This is basically a tug boat, so the prop blades should look like big elephant ears. Not the raked, more modern design you see on performance boats.

Original prop was a 141/4?17 p (not sure if original equipment) second was a loaner 151/2? 15 p borrowed from my friend with same boat running 30+ on a GPS. Third was a 15?17 4 blade that performed worse than first and last is a Mercury black diamond 15 1/2?15 p pontoon prop ( more cup) suggested by propmd. Has been doing this since I have owned it. It is by far a ton better than it was, but still not 100%. Thus the reason for the question about the pontoons being moved

 

[ahicks]

Oh, heck ya! I get the reason you're looking at this. I think many of us would be for sure! Sometimes sharing the back story, especially what you've already tried, can be productive and generate ideas you haven't tried.

The buddy running 30mph with the same boat. Thinking not the same boat, but maybe similar? What's the difference? Is he running a set of big tubes? Can you elaborate?

Have you spoken with propmd regarding your results with their suggested prop? Looks like they have a "pitch exchange program" advertised on their web site. Your results with their recommended prop in mind, you might be able to work something out to allow another try.

 

[98fatboy]

Pitch exchange is for ss props. Difference between mine and his, is his is two years newer and the toons are flush with back of deck, his foot/drive is in clean water. My toons are 24ft 23 inch diameter so says Harris after I contacted them. Same as my friends.thats the reason for asking about moving the toons or cutting them down

 

[ahicks]

You might want to confirm his is the diameter you think it is. I have 24" toons with a Honda 90 (400 lbs). I can't imagine any more weight than that on those 'toons.

 

[Cat nip]

Its worth a shot to move the logs forward if you dont mind doing it while knowing they might need to be moved back again. You would also need to shift weight on the toon forward to account for the change in log position. Someone on here told.me that physics says if you are not adding or subtracting weight the toons will stay at the same flotation level if moving weight. But it might take moving the batteries, helm and some other stuff forward to get the balance correct. I would try it but I like to make a mountain out of a mole hill.