high rpm on df140

[isudoc03]

I currently have a aluminum prop on my Suzuki four stroke 140 hp. At WOT I am at about 6700 rpms which is too high according to manual. Prop says 3x14x19. I assume that is 14 diameter and 19 pitch. I was thinking I need to switch to a 20 or 21 pitch prop. The props that I find have a diameter of 12-3/4 and 13-1/4. Is the diameter difference going to be a big deal?

thanks

 

[Campylobacter]

Re: high rpm on df140

Your are correct about the pitch needing to be higher, WOT should be below 6200 for that motor. Don't worry about the diameter, it is the pitch that make the most difference.

 

[LORDY611]

Re: high rpm on df140

My recent experience tells me that you may want to verify your actual RPM. Tach could be wrong, and would be less $ to replace than a prop. Just a thought.

 

[Irv964]

Re: high rpm on df140

My recent experience tells me that you may want to verify your actual RPM. Tach could be wrong, and would be less $ to replace than a prop. Just a thought.

I agree, going to a 20 will bring your rpm down to 6500 and a 21 down to 6300, still too high for that motor. Like said above, I would verify your tach first before purchasing another higher pitched prop........Irv964

 

[isudoc03]

Re: high rpm on df140

What is the best way to check my tach? Buy another tach and see if it is the same?

 

[Silvertip]

Re: high rpm on df140

You can start by telling us what the idle RPM is on your current tach. I don't know off hand what the idle rpm is for that specific engine but I suspect it is in the 700 - 800 RPM range. Since the tach is 600 RPM off on the top end (approximately 10%), you might have a 900 RPM idle speed which would be the tip off that the tach is incorrect. Otherwise, you could rent a timing light with a built-in tach. Most have an inductive pickup that you simply clip onto a spark plug wire.