is 5500 RPM too low?

[Cheapie408]

I have a parker 2120 pilot house, originally had a 15x17p 3 blade stainless prop, WOT 6k to 6.2k top speed 42mph

switched to a 14.5x15p 4 blade stainless I lost about I'm now getting WOT of 5500 to 5600rpm top speed at about 35-36mph.

13.5" 15p 4 blade would get me back to 6k RPM. Sounds about right?

[TownsendsFJR1300]

What engine?

[Cheapie408]

Sorry, it's a 2005 F200

[DennisG01]

You should not have LOST RPM by going to a 15". You should have increased RPM. Something else is going on - whether it's a mechanical issue or possibly user error. What you could do, based on your initial findings is to go to a 15x19". That should get you just shy of 6K.

[Cheapie408]

You should not have LOST RPM by going to a 15". You should have increased RPM. Something else is going on - whether it's a mechanical issue or possibly user error. What you could do, based on your initial findings is to go to a 15x19". That should get you just shy of 6K.

lost RPM because I went from a 3 blade toa 4 blade


Here's my comparison

original 3 blade SS 15x17p
WOT @ 6k RPM 42mph


4 blade 14.5x15p
WOT @ 5500 RPM @ 36 mph

I believe the F200 WOT should be between 5000-6000

I'm wondering if there is a benefit if I can find a balance prop that will get me back up to 6k RPM wot. will I gain anything or am I already at the sweet spot for a 4 blade prop with this motor.

[99yam40]

You should not have LOST RPM by going to a 15". You should have increased RPM. Something else is going on - whether it's a mechanical issue or possibly user error. What you could do, based on your initial findings is to go to a 15x19". That should get you just shy of 6K.

he went from a 3 blade prop to a 4 blade.
extra blade does make a difference

OP why did you not like the original prop?

[Cheapie408]

he went from a 3 blade prop to a 4 blade.
extra blade does make a difference

OP why did you not like the original prop?

The prop was fine when I had no load and just me and one other person and calm days.

When I'm fully loaded with four guys in 5ft seas, there was a lot of spinning of the props but barely any moving of the boat when I'm trying to climb those waves.

The 14.5x15 perform very nicely yesterday the only thing is that it's not reaching 6,000 RPM. I was cruising at 27 mph at 4500 RPM getting approximately two and a half miles per gallon.

I guess I'm fine with this prop but if I can make it any better I'm all ears

[99yam40]

The prop was fine when I had no load and just me and one other person and calm days.

When I'm fully loaded with four guys in 5ft seas, there was a lot of spinning of the props but barely any moving of the boat when I'm trying to climb those waves.

The 14.5x15 perform very nicely yesterday the only thing is that it's not reaching 6,000 RPM. I was cruising at 27 mph at 4500 RPM getting approximately two and a half miles per gallon.

I guess I'm fine with this prop but if I can make it any better I'm all ears

did you run the new prop with the light and heavy loads to see how it performs with both?
may need to swap props depending on how you plan to run the boat.
switching from 3 to four blade is not always easy to figure out

[boscoe99]

Yes.

Over propping that motor will make it feel like a dog. With all due respects to my Boscoe boy.

[boscoe99]

lost RPM because I went from a 3 blade toa 4 blade


Here's my comparison

original 3 blade SS 15x17p
WOT @ 6k RPM 42mph


4 blade 14.5x15p
WOT @ 5500 RPM @ 36 mph

I believe the F200 WOT should be between 5000-6000

I'm wondering if there is a benefit if I can find a balance prop that will get me back up to 6k RPM wot. will I gain anything or am I already at the sweet spot for a 4 blade prop with this motor.

Nope. You need to be at or near 6000 RPM. WOT. Boat loaded. Motor trimmed up just to the point of best mileage for your cruise RPM.

[95Whaler]

What does the motor manual say for max HP and max RPM?h

[DennisG01]

I missed the part where you wrote you went to a 4-blade. Typically, though, you drop 1" of pitch when you go from 3-blade to 4-blade and that keeps about the same WOT RPM. But you went down 2" and STILL lost 600RPM. Assuming all other variables remained the same, that's a very significant difference. I suppose the smaller diameter had something to do with it, too - but still... 600 RPM? I guess another factor is the brand/style of prop.

I've read A LOT of good things about Ken at Prop Gods - you may want to reach out to him. He certainly knows more than me.

[Cheapie408]

So this is straight out of the manual. So according to that, then I am in range correct?

Yamaha F200 WOT.jpg

[boscoe99]

When changing brands and models and types of propellers all bets are off with respect to what the outcome will be. Too many variables.

[boscoe99]

So this is straight out of the manual. So according to that, then I am in range correct?

Yes. In the range. The range for mediocrity .