Pontoon boat prop/outboard position help

[Speedwagon]

It's a 2000(ish) pontoon boat, with a 40hp Johnson on the back. He's a fairly large guy, and has some larger friends. The boat is ok with just his family on it(wife and one kid), but when it's a bunch of adults, he doesn't like the way the boat feels. Too slow I guess.

He'd LIKE an 80hp 4 stroke on the back, but that's alot of money. I'm going to try to figure out the WOT and current pitch tomorrow, as I haven't bothered to check before.

But before I get that info, any insight on how to make this boat perform better?

 

[Speedwagon]

Re: My friend needs better performance!

Re: My friend needs better performance!

Didn't get a chance to take the boat in the water today, and the prop pitch is under the nut and washer, so I couldn't see what it is yet.

But here's some pics of the current setup...

 

[Texasmark]

Re: Pontoon boat prop/outboard position help

I'm not a toon guy, but you have that engine tucked way too far in. The toons are long and thin.

That would tend to make it nose heavy and plow thru the water which increases hull drag and when lots of folks are aboard, it may be the reason for the lackluster performance.............plus it probably makes steering awkward; boat tends to want to steer it'self and ignore the helm's commands.

First thing I would do is move the tilt pin to the last hole (2 more holes toward the rear). Will only take a minute, cost nothing, and could solve your problem.

Let us know and thanks for the pic......pic, worth a thousand words.

Mark

 

[roscoe]

Re: Pontoon boat prop/outboard position help

Not a toon guy either, but judging by the old waterline, motor appears to be way too low.

The waterline is half way up the motor leg.

What does this guy really expect from an overloaded pontoon?
And underpowered as well.

 

[roscoe]

Re: Pontoon boat prop/outboard position help

How big is this boat?

 

[rickdb1boat]

Re: Pontoon boat prop/outboard position help

It would be a whole lot easier to judge motor height if the picture was taken with the boat in the water all the way. It does look like it's sitting low though....

 

[Speedwagon]

Re: Pontoon boat prop/outboard position help

I'm not a toon guy, but you have that engine tucked way too far in. The toons are long and thin.

That would tend to make it nose heavy and plow thru the water which increases hull drag and when lots of folks are aboard, it may be the reason for the lackluster performance.............plus it probably makes steering awkward; boat tends to want to steer it'self and ignore the helm's commands.

First thing I would do is move the tilt pin to the last hole (2 more holes toward the rear). Will only take a minute, cost nothing, and could solve your problem.

Let us know and thanks for the pic......pic, worth a thousand words.

Mark

I was thinking that it probably was tucked in too far, and that's why I got the pics of everything. I'll move it out to that hole, and get a pic while it sits in the water as well. Probably report back tomorrow morning with pics at least.

 

[Speedwagon]

Re: Pontoon boat prop/outboard position help

Haven't been able to run the boat yet, but the prop is a 12.25x15. And after adjusting the trim bolt, here's some more pics. The specs for the 2006 Crest II, indicates that an 18' toon has a 10 person capacity, which is what this boat is rated at, and 75hp max engine(same as this boat). So my educated guess is that this is an 18' toon, with 24" pontoons on it.

Sitting in the water, nobody in the boat:

Out of the water, motor all the way in:

 

[Texasmark]

Re: Pontoon boat prop/outboard position help

Tilt looks a whole lot better. Should make a marked improvement in handling.

I agree with Roscoe. Engine does seem to be quite low on the bracket. But what we don't know is what does the wake look like coming off the front of the transom bracket when at WOT.

Maybe you have to have the engine that low to keep the water above the antivent plate at WOT.

But if that's not a problem, I'd grab the last 2 holes and ger her up out of the water. No question about it reducing drag.....but if we get too high we might ventilate and we don't want that.

Might "hook her up", have a look see and get back with us.

Nice picks, really clear.

Mark

 

[Speedwagon]

Re: Pontoon boat prop/outboard position help

Ok, here we go. I was out of town last week, and just got out on the boat.

3 adults, 4 kids on board. Max RPM I could achieve was 4200, at 14mph(GPS) heading with the wind. Dropped to around 12mph against the wind. Doesn't have a trim gauge, but I was playing with the trim, and didn't notice much difference. The only time I noticed anything, was fully trimmed in, then I could hear the motor lugging a bit more.

 

[Texasmark]

Re: Pontoon boat prop/outboard position help

Hey Speedwagon.

Glad to get some feedback off this after participating in it and wondering how things worked out.

Your numbers don't mean a whole lot as you didn't publish initial numbers. Can't tell if we did you any good .

Apparently you haven't had the opportunity to raise it a hole or two per roscoe and rick's concerns.

You still have work to do (in my opinion). 4200 rpm running with the wind and less speed, hence less rpm's against it, and lugging when tucked in more indicates that you need to seriously consider the lift and then if you are still low in rpm's dropping your prop pitch.

However, 14 mph with a 40 hp engine on that large a boat seems pretty good to me.......but I'm not a toon guy..(grin)....but the rpm's still seem low. (Don't have WOT data for that engine.)

Mark

 

[Speedwagon]

Re: Pontoon boat prop/outboard position help

Well, I did raise the engine after that post, but lost power at the house, so I couldn't reply last night.

Got about the same results after raising the engine up one hole though. It did sound like it wanted to blow out though, and trimming up did result in a blowout much sooner than before.

 

[Texasmark]

Re: Pontoon boat prop/outboard position help

Well, maybe you want to put her back down and figure you got all you're going to get and go after the prop to get the rpm's up.

Do I see barnacles on the toons? If they are crudded up, that can have a very large impact on your speed. They need to be slick, just like the bottom of a conventional hull. Check into that first then the prop thing.

Mark

 

[Speedwagon]

Re: Pontoon boat prop/outboard position help

Noone knows what this engine is supposed to run at? Or have a recommendations on what pitch to change it to?

 

[walleyehed]

Re: Pontoon boat prop/outboard position help

5500-up.........

 

[Texasmark]

Re: Pontoon boat prop/outboard position help

People talk about 200-250 rpm per inch of pitch decline with the same geometry on the same rig. So 5500-4200 is 1300/250 = 5" less pitch.

SWAG from the pic, says that you may be running a 15 now. So that would drop you to a 10" pitch. Heck of a lot of drop. But 4200 is way low.

Sure your engine is putting out like it should?

Wish I knew your gear ratio and had an OMC catalog.

In the Merc lineup, 40 hp, with a 2:1 gearbox will run an 8 to 19P so, if you were 2:1 a 10" pitch is in line on a large boat like you are running.

Tell you what I bet. Your engine is carboned up from overloading it since you had it. Why don't you do a decarb first and then recheck your WOT rpm's.

Very well be that a decarb will buy you 200-300 rpm's and you then only drop 3 or 4 inches in pitch which will benefit your engine and may get you a mile or two more speed.

I looked at the pics again, and the lower unit and the pontoons seem to be gungied up. This will slow you down and lug the engine.

Mark

 

[steelespike]

Re: Pontoon boat prop/outboard position help

Sounds like Tmark has you headed in the right direction.
Unfortunately toons are notoriusly slow.Especiall;y loaded.An 80 probably wouldn't give much more than 4 or 5 mph loaded and at a tremendous use of fuel.
There are some after market things you can do to help.
you can add a belly skin and there are a number of 3rd pontoon options.I think a 3rd pontoon would add allmost as much speed as an 80 hp with better flotation and no fuel cost.