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Prop issue update help

C

cuzzx

Member
"Ok this is my latest finding

"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."
 
"It is hard to answer this typ

"It is hard to answer this type of question from the desk without more info.However.Is this a new boat or has its performance deterioated?.What type and size is the prop?.At a guess or to give you a starting point ,dont rely on the speedo for accuracy a gps is the only way to go.You probably have a fuel / carby / intake problem ,if cleaning the carbys doesnt fix or improve the problem you will need to look deeper into the motor."
 
"1994 stardust pontoon with a

"1994 stardust pontoon with a 1994 Mariner running a 13x19 SS. also

7. the motor in the best rpm position, water line is 4inchs above the cavition plate.
215006.jpg
motor water line
 
"Was checking out the new big

"Was checking out the new big foot from Mercury and in one part it said that is better for the foot to be below the water line;
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.
Does this mean that my motor might be ok where its at?
Still have proping problem."
 
If it was running ok ?lets ass

If it was running ok ?lets assume and this problem has developed??Maybe you have water in one of your pontoons??.
 
"Have talked with 3 different

"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."
 
"I agree that the prop you are

"I agree that the prop you are running is probably too big .However if you look at the first question i asked you ,was the boat running ok and has this problem developed ????.I hope the new prop solves your problem,"
 
"David, I just bought this mot

"David, I just bought this motor and have only ran it 2 times.
The boat it came off of was a center console.

Everyone shop wise told me that it should get 7 to 9 miles per gallon with the new prop.

Thanks"
 
"Replaced the prop this past w

"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."
 
"In the photo you have what lo

"In the photo you have what looks like a stainless prop,id stick with the stainless .It is starting to sound you could be underpowered ???"
 
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