prop change to help rpm and speed?

[jeff6898]

16ft bass boat 85HP Evinrude

Has a 19 pitch prop on it.
It only runs wot at 4500 rpms and 43 mph. PLanes fast no problem there Motor runs great 140 compression all cylinders great spark runs real smooth. Will going to a 17 pitch help rpm's and speed?

 

[Irv964]

Re: prop change to help rpm and speed?

What's your max RPM fully trimmed etc? What max rpm is the motor rated for?
A 17P will increase your rpm's but in most cases will reduce your top speed.

 

[jeff6898]

Re: prop change to help rpm and speed?

ax
I am getting fully trimmed is 4500 the motor is rated at 5500 wot

 

[codertimt]

Re: prop change to help rpm and speed?

Before you go buying a prop, I would verify your tach readings. Right now your numbers don't calculate. Is the speed via gps or speedometer?

I'm assuming we're talking a newer model 85...at least mid 80s? If so, you should have a 2:1 gear ratio. So if you're running low 40s then you're turning closer to 5500 rpms and if you're really only turning 4500, then you're actually only going mid 30s.

I see no reason why a good running 85 couldn't turn a 19" prop well on a small bass boat, so I'm guessing it's the tach and would start there... That's just my $0.02 though...I'd wait for some other to weigh in...

 

[steelespike]

Re: prop change to help rpm and speed?

check the tach, sounds like a good place to start to me.

 

[jeff6898]

Re: prop change to help rpm and speed?

It is a 1979 evinrude 85hp if that makes a differance, I wil check the tac though it is old.

 

[bob01081969]

Re: prop change to help rpm and speed?

I have a 1988 Ranger 330v 16ft with a evinrude 140 and with a 19 pitch prop I would fly up on plane but speed was slow about 48 mph @4900 rpm I put a 21 pitch raker and wow 54mph @5300 rpm I moved up to a 24 pitch this season running 62 mph hi rpm's 6100 but thats fine I know a lot of guys turning a lot more rpm's on these V4 next year I am putting a set of 1987 heads to get more rpm's and speed but I will also add a nose cone and water pick up. If you want more speed you need more rpm go slow I had a lot of guys with props and knowlage help me

 

[GiMLit]

Re: prop change to help rpm and speed?

I have a 1988 Ranger 330v 16ft with a evinrude 140 and with a 19 pitch prop I would fly up on plane but speed was slow about 48 mph @4900 rpm I put a 21 pitch raker and wow 54mph @5300 rpm I moved up to a 24 pitch this season running 62 mph hi rpm's 6100 but thats fine I know a lot of guys turning a lot more rpm's on these V4 next year I am putting a set of 1987 heads to get more rpm's and speed but I will also add a nose cone and water pick up. If you want more speed you need more rpm go slow I had a lot of guys with props and knowlage help me

More pitch and you are getting more RPM and more Top Speed?
I was under the understanding more pitch = less RPM Less hole shot and more top speed