Trying to get more speed

[ahicks]

Re: the 5", not sure it would either. Just wanted to add that In addition to the old 15" short shaft engines we used to see frequently, there are now 25" engines. No clue what the Big Foot is, or the OMC you were looking at.

We have 2 boats. A '99 24' w/40hp Johnson based in Mi., and a newer 20' w/50hp Honda based in Fl. Trim will make a difference on both when lightly loaded, but nothing worth talking about. Maybe a couple hundred rpm. Both boats are propped to get max rated rpm, and both are capable of 18-19mph on GPS with 2 people on board.

If you don't like the concept of a pontoon "on plane" both of these boats clearly do something that puts them on top, and neither have any special lift equipment to do that. I find boats with larger tubes do this pretty easily. Ours are both 25" and will stay "on top" down to about 12mph. That's the speed we generally run at "cruise" setting when we have some ground to cover.

Our 20' boat sits low in back as well. I'm sure part of it is because of the Honda, but there's a crazy big fuel tank built into the center pod/engine mount as well. The weight of 20+ gallons of gas doesn't help a thing! I've often thought a more efficient setup would have the fuel tank and battery both located forward.

Last,, one other factor regarding how low they sit may have something to do with pontoon location. If the floor plan is set up to allow the engine to be set up between the pontoons, that boat is going to float noticeably higher in back than one set up where the engine is clearly located well in back of the pontoons.

 

[edsjr01]

Bigfoot is 25" and Optimax is 20"

I can't wrap my head around the trim being there with absolutely no function except to eliminate prop blowout in turns....pontoons arent exactly performance boats so I dont see a lot of high speed turns like a skier or tube is being pulled so why the worry about blowout?

I wonder if a 4 blade prop would help? I'm just thinking out loud, havent even checked to see if there is one available for the Bigfoot, which takes a special prop

 

[ahicks]

You might be surprised how easy it is to "blow out" an outboard on a pontoon boat. Imagine the tracking force created by 2 parallel pontoons moving through the water. Now imagine a rudder on the back of those cranked to one side suddenly. The back/trailing side of that is going to have a tremendous amount of vacuum present, easily enough to pull air from above the water's surface trying to equalize the pressure. If the engine's cavitation plate is too high, it's not hard to see how air above it could get sucked into that prop....

We use our "trim" to avoid obstacles and weeds primarily, trailering to a lesser extent. Even on rigs with more power pulling skiers, the trim isn't used much.

 

[Sea Rider]

I've run my 24' pontoon boat with three different engines. I never noticed the trim setting making any difference. .... And the trim setting that will most raise the rear of the boat and lower the front is .... no trim.

Agreed on that 0 trim and deck weight evenly balanced, will add spot on engine/transom height...

Happy Boating

 

[Jeep Man]

Bigfoot is 25" and Optimax is 20"

I can't wrap my head around the trim being there with absolutely no function except to eliminate prop blowout in turns....pontoons arent exactly performance boats so I dont see a lot of high speed turns like a skier or tube is being pulled so why the worry about blowout?

I wonder if a 4 blade prop would help? I'm just thinking out loud, havent even checked to see if there is one available for the Bigfoot, which takes a special prop

My Bigfoot is an `08 and is a long shaft (20``) as most are. If your serial number has an "X" in it, It will be an extra long (25").

 

[HotTommy]

Yeah, I think the Bigfoot designation means it has a larger, stronger lower unit with perhaps a different gear ratio. It does not tell you how long the leg is.

BTW, I operated my 24' pontoon boat last summer with a 150 HP, 25" leg motor with an unknown 3-blade prop turning an unknown RPM. I knew it was too long so I raised it as much as possible, but the prop was still too low. It sounded good and had a peak speed of about 27 MPH with a light load. I now have a 115 HP, 20" leg motor turning a 4-blade prop that peaks out near the top of the desired RPM band. It also goes about 27 MPH. My point is that you shouldn't look only at HP in choosing your motor. The entire package is important.