prop issue update, ---help

[cuzzx]

Ok this is my latest finding on my pontoon motor prop issues.
20ft toon with a 75hp mariner, total weight at 1850 lbs.

this is with a new tach and an old mph guage hooked to motor.

1. motor down all the way, motor turns 2300rpm at 18 miles per.

2. trimmed motor out until it started to bog, back off by reversing tilt back down until it ran smooth again. motor turned 3000rpm at 20 mph.

3. as toon moved across the water for a distance of a mile or so the rpm picked up to 4200 with mph at 20.

4. then rpm picked up alittle more within another mile to 5000r's, mph20.

5. ran this test three times with same .

6. now, I ran 10 miles on a calm bay and it took 6 gallons of gas also.4 people in Toon with 100lbs of fishing gear , battery, trolling motor.

7. the motor in the best rpm position, water line is 4inchs above the cavition plate.

 

[cuzzx]

Re: prop issue update, ---help

You guys talk to me about my problem, help me out.

also will checking out different sites I found this on the Mercury site;

BigFoot is built with a TALLER, MORE DURABLE GEARCASE that places the propeller deeper in the water. The lower position keeps the BigFoot prop below turbulent water, allowing it to operate in cleaner, less aerated water for dramatically improved performance.

Could this mean that my foot might be ok if I can get the prop/rpm problem fixed and then the gas milage problem, 6 gallons in ten miles.

 

[steelespike]

Re: prop issue update, ---help

First of all it appears your rpm is too low.What size prop do you have?
Rpm increase with no change in speed sounds like it is venting.I've noticed my toon will do the same no power trim so I have to throttle back little then can usually try again.
At WOT(wide open throttle)the 75 will use about 7.5 gallons per hour.So the question would be how long did you run at WOT and how long total?
If it was venting that is surely a waste.
Sweet spot for toons is between 6 to 9 mph can actually get better mileage than a runabout at the same speed when pushed beyond those speeds mileage drops rapidly.

 

[codertimt]

Re: prop issue update, ---help

So are you still trying to run the 19" prop as you were in your earlier posts? Not trying to be harsh, but unless that has changed the answer from the experts here is still going to be you need to drop in pitch... Both K.D. and Silvertip(who responded to the other messages) pretty much know what they're doing/saying.

 

[cuzzx]

Re: prop issue update, ---help

So are you still trying to run the 19" prop as you were in your earlier posts? Not trying to be harsh, but unless that has changed the answer from the experts here is still going to be you need to drop in pitch... Both K.D. and Silvertip(who responded to the other messages) pretty much know what they're doing/saying.

Yes somewhere here I have added an update to my prop problem, and can't find it.

Ok when I replied to with this it all came back above.

20ft Toon with a 94' 75hp Mariner running a 13x19SS prop.

The toon gained rpm over a mile or so run but the speed stayed the same and it used alot of gas. Tried this 3 different times and each run was just about the same.

 

[cuzzx]

Re: prop issue update, ---help

Have talked with 3 different boat shops and each one told me the same thing.

The prop that I'm running has to much pitch.

Will be going from a 13x19ss to a 13 3/4 x 15 alu.

The gas , all 3 said that with my Toon and prop it is like driving a 4speed truck, pulling my pontoon and driving all over town.

Have a new 13 3/4 x 15 that I'm going to try this weekend.

And a new speedo-meter.

 

[branman1971]

Re: prop issue update, ---help

Hey Cuzz,

I got a timing light today and took my pontoon out for some test runs with the GPS also. Turns out the tach I have is not reading accurately. Had only me, some gear, a couple batteries, and about 10gallons of fuel onboard. With my 13.75 x 15 prop on 20ft pontoon I got:

2000rpm @6.5mph
3000rpm @11mph
4000rpm @16mph
4500rpm @18mph

I couldn't get over 4500rpm but I can get to 4500 somewhat quick. Think I will go to a 13pitch prop and see what it does. Just some info for you from another guy with a 20ft pontoon and a comparable motor.

 

[cuzzx]

Re: prop issue update, ---help

Replaced the prop this past weekend.
Put a 13 3/4 x 15 alu. prop on.
RPM was around 5200.
Put a new MPH guage on that connected to my Humminbird 656, It did not work unless the Toon was turning around. The old guage said 16 MPH.

I'm still have gas problems also. I'm getting around one mile to the gallon WOT.

 

[ipodfansmail]

hey

hey

May i have a personal question? counld u sent me your email address?My email is ipodfansmail@gmail.com, thx, man.