Reply With QuoteProp sounds too big for the application if you are not reaching the correct RPM range.
To clarify it has never ran any higher RPM than 4100 or is this a problem that just started recently?
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Minnow
2019 mercury 115 prods CT
Motor is on a pontoon, Lowe SF212 walk thru. Max RPM is only 4100. Prop is factory, black max 15.25 x 15.
I am nowhere near the max RPMs that I should be. Motor runs and sounds fine.
Thoughts?
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Prop sounds too big for the application if you are not reaching the correct RPM range.
To clarify it has never ran any higher RPM than 4100 or is this a problem that just started recently?
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Slabmaster II
What he said and are you sure your tach is not out of wack?
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It was easier to tell when the 2 strokes where in the right range. These 4 strokes don't make a lot of noise. It would be hard to tell if the tach was off
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Minnow
It has never ran higher than 4100. I bought it new from a dealer. I just now noticed I wasn't getting the minimum full throttle range (5300-6300).
I am fairly certain it is not the tach. In the video below, it is the same setup that I have, except my motor is newer. He is getting 30 mph @ 5800. My max is 21 mph @ 4100. This only difference is he has a 13P prop, I have a 15P.
2018 Lowe SF 212 WT - YouTube
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Operating RPM should be between 5000-6000. 4200 is way to low to be running that motor under load. If your tach is right then my experience tells me that it would take roughly a 11 or 12 inch pitch prop to achieve proper rpm which seems awful small for that set up. I agree with the guys above that you might just have a tach problem. Also the motor could be mounted way to low on transom. You might try raising motor a couple of bolt holes and see what that does while making sure you don’t lose water pressure. Pontoons can be really tricky to set up at times.
We must have been typing at same time. If that guy is getting that much increase with 13 verses 15 I’d try the 13 but still think motor height might have something to do with it.
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Crappie Wall Hanger II
Is motor a 25" shaft ? Long shaft and not a short shaft?
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What I'm getting at if some how a 20" motor was installed. Prop. Isn't deep enough , below water line and can be cavitating.
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Cavitation would allow the motor to unload and hit the rev limiter or in the very least it would cavitate rev up and then get a bite on the water again Porpoising. As far as the tach. Mercury makes Vessel View. It is a module that hooks to the ecu of the outboard, then uploads data to any bluetooth capabile device. It is an awesome diagnostic tool, tells, speed, rpm, temp, fuel usage, flowrate, water pressure, oil temp and presure. Any trouble codes, warnings and maintenance intervals. Surely a shop has one. In all honesty they are not very expensive if you are going to do your own maintenance and trouble shooting work paying shop charges twice would cover its cost.Originally Posted by Mbsbeek
A prop shop may have some loaners and help you figure out the best prop for the boat.
The love for fishing is one of the best gifts you can pass along
