Disappointing speed...

[curtiscapk]

Well I made the mistake of remmbering gps this weekend.

12 mph at 4750 wot...
Recommended range is 4750 to 5250.

Granted its a 24 footer with all stock wood benches Inch thick frames all the way around we had 10 people a real dog and a rat dog and two coolers and my tool box ( one day I won't bring it and I'll need it), it was also pretty soaked already from the rain the night before.

The 115 has a 14 x 13 prop.

Last time with 8 aboard and not water logged and one less cooler I could get 5000 but didn't have gps then. Motor seems to run fine I haven't done recent compression check but last year when we got it all four had 115 pounds.
One thing I have not done since last year is used seafoam in it, gonna try that next maybe it's gunky carbs..

I know its a big ass pig, but was at least hoping for 20..

What do you guys think..

[bruuuuce]

what kind of shape is your prop in? could it be chipped or out of pitch? Plugs?

[curtiscapk]

Brand new last year not a ding or nick it's perfect...

Plugs looked fine after last outing.

[badmoonrising]

My max speed at WOT is about 18 mph (GPS), slips slightly if there's alot of marine growth but I have been scrubbing the bottom every few weeks...

[jim454]

mine runs about 18mph with the 50hp honda. I really don't think a few more mph will make much of a difference.

[oldmn19]

Our 22 ft w/90 hp Yamaha will gps 24-25 with just me and full tank. With 4 folks, cooler, full tank I get 20-22 gps depending on smooth or choppy water.

[MrGadget]

With 10 people on board (~1500 lbs) plus your gear, 20 mph would be wishful thinking. Go out by yourself with the least gear possible and the GPS and see what you get. Mine is half again bigger than yours, with twice the motor, and with a load of passengers I don't think I can break 15 mph either, but I can make 26 mph alone. I'd bet with the extra people you can't get up on plane, so you're driving in "displacement mode" which has a mechanical limit defined by physics. Tubes and strakes only provide lift to some limit in weight, and with that many people you've probably exceeded that.

For Displacement Hulls:
Max Speed = Length-at-Water-Line (LWL) x .5 x 1.34
For yours: 24 x .5 x 1.34 = 16 mph

This suggests that a little more motor would get you to 16 mph but no higher without planing.

[JohnO]

With 10 people on board (~1500 lbs) plus your gear, 20 mph would be wishful thinking. Go out by yourself with the least gear possible and the GPS and see what you get. Mine is half again bigger than yours, with twice the motor, and with a load of passengers I don't think I can break 15 mph either, but I can make 26 mph alone. I'd bet with the extra people you can't get up on plane, so you're driving in "displacement mode" which has a mechanical limit defined by physics. Tubes and strakes only provide lift to some limit in weight, and with that many people you've probably exceeded that.

For Displacement Hulls:
Max Speed = Length-at-Water-Line (LWL) x .5 x 1.34
For yours: 24 x .5 x 1.34 = 16 mph

This suggests that a little more motor would get you to 16 mph but no higher without planing.

http://www.2hulls.com/archive/Gen%20Art ... aning.html Discusses the differences between planing and displacement catamarans. They mention an additional factor called "Hull Fineness" which affects the calculations.

The equation above is for an average monohull displacment hull. A pontoon is closer to a catamaran (or trimaran) so the speed will be a bit more than what the equation gives. Catamarans tend to have very "fine" hulls separated by a space. They outperform single hull displacements ships.

I've not been able to find exactly what the change would be but it does exist. (read a lot about cataran design and everyone mentions it but no one defines it)

(wanted to fully research this but have run out of time)

[tkrein]

just a ? have you done a compression check. change fule does it seem slower than when you were pulling tubers. and the biggest have you changed anything lately

[jim454]

Brand new last year not a ding or nick it's perfect...

Plugs looked fine after last outing.

Curt,
I came across a guy on my river trip that had a toon very similar to yours. He claimed his top speed was 35 mph, I believe him after he blew past me. He had a party barge with a 115 merc 2 stroke.

[Alohatoon1]

He lied.

24 ft, double tubes, 115hp = 23-27mph with a medium load unless you have some extremely large diameter pontoons, like 26"

Maybe he was going downstream in an 8mph current.

[jim454]

He lied.

24 ft, double tubes, 115hp = 23-27mph with a medium load unless you have some extremely large diameter pontoons, like 26"

Maybe he was going downstream in an 8mph current.

[WaltF]

Ya, 10 people on board, with junk?
It aint gonna fly..

Kick everyone off, and on a clam day, whip that puppy up, and ill bet you get 20-25.

But then, these thAngs aint built for speed....
Theyre built for BEADS!



Inless youre some kinda nut case with 3 toons, strakes, and 200+hp strapped on her!!

..oh wait.. there are a few of those very nut cases on this forum...

[dockholiday]

Ya, 10 people on board, with junk?
It aint gonna fly..

Kick everyone off, and on a clam day, whip that puppy up, and ill bet you get 20-25.

But then, these thAngs aint built for speed....
Theyre built for BEADS!



Inless youre some kinda nut case with 3 toons, strakes, and 200+hp strapped on her!!

..oh wait.. there are a few of those very nut cases on this forum...

Yep but I only have 150hp..............AAAAAAAAAAAAAAAHHHHHHHHHHHHH NNNNNNNNNNUUUUUUUUUTTTTTTTTTSSSSSSSSSSSSS
doc

[curtiscapk]

Dang Walt,

you callin my stuff junk


I know I SHOULD get more but haven't freakin had time to get back down to check anything out...

Vacation next two weekends to Dauphin Island Bama..

lookin like middle of August before we can, so I'll check plugs carbs and comp and fly solo, and let you guys know.

We really don't mind slow but I sure would like to dump the little bastards off the tube. And at least smoke my bro's 50 hp 20 footer