Chosing a Better Prop

[freeltm]

I have a 1997 Hurricane 206LC Fundeck (20' 6") with a 1997 Honda 90 outboard. Currently the boat is runing a 13 3/4" 15P aluminum propeller. The engine is turning 3500 RPM at WOT. As I understand it should be turning more like 5500 RPM at WOT. It planes out fine with a light load (3-4 people) and tops out at about 28mph under good conditions. It will not get on plane with 6 or more people onboard.

I like to cruise and kneeboard with 4-6 passengers usually. What propeller would you recommend for this set-up? I realize that this boat will never be terribly fast, but the current prop does not seem right. Engine runs fine otherwise.

Thanks.

 

[steelespike]

Re: Chosing a Better Prop

That boat is a load at 2400 lbs dry weight.
You might check that the carbs open all the way, timing set right and advancing as it should.Check that the motor is at an ideal height.
The antivent plate (just above the prop) about even with the bottom of the boat.
If your sure everything is right a 13" prop would give you about 5900 with 3 or 4 aboard,may get you on plane with 6 aboard.
you have to be careful with a light load.A 4 blade is the same size might help a little more.

 

[jestor68]

Re: Chosing a Better Prop

If the motor is only turning 3500 rpm with a 15" prop, how is dropping 2 inches going to get 5900?

 

[steelespike]

Re: Chosing a Better Prop

He stated it turns 5500 with 3 or 4 aboard at 28 mph.

 

[jestor68]

Re: Chosing a Better Prop

I have a 1997 Hurricane 206LC Fundeck (20' 6") with a 1997 Honda 90 outboard. Currently the boat is runing a 13 3/4" 15P aluminum propeller. The engine is turning 3500 RPM at WOT. As I understand it should be turning more like 5500 RPM at WOT.

That's what I read.

 

[jestor68]

Re: Chosing a Better Prop

The Merc prop selector comes up with a 14/15 inch for a Merc 4 stroke 90 on a boat like his. So I assume the Honda ought to be able to handle something similar.

How long have you owned this boat? It sounds like you have a motor way overdue for a tune up, or it's just plain worn out. Motors that have lost much of their compression can still run "fine"; just don't develope the horse power they used to.

 

[freeltm]

Re: Chosing a Better Prop

The Merc prop selector comes up with a 14/15 inch for a Merc 4 stroke 90 on a boat like his. So I assume the Honda ought to be able to handle something similar.

How long have you owned this boat? It sounds like you have a motor way overdue for a tune up, or it's just plain worn out. Motors that have lost much of their compression can still run "fine"; just don't develope the horse power they used to.

I haven't owned the boat that long. But the motor runs great. I'm thinking that the tach is not reading correctly after doing a little more research yesterday. I'm going to investigate that a little further.

Thanks for the input.

 

[steelespike]

Re: Chosing a Better Prop

That's what I read.

Actually a 15" prop at 28 should be turning about 5100. The post wording confused me,not hard to do.
It does appear that the tach may be off.
With 7 people the weight would be over 4000,a lot for 90 hp.Maybe we shouldn't expect it to plane
though it does seem a 15" should do better with a 2.33 ratio. I wonder what the rpm and speed would be with just a driver aboard?

 

[freeltm]

Re: Chosing a Better Prop

Actually a 15" prop at 28 should be turning about 5100. The post wording confused me,not hard to do.
It does appear that the tach may be off.
With 7 people the weight would be over 4000,a lot for 90 hp.Maybe we shouldn't expect it to plane
though it does seem a 15" should do better with a 2.33 ratio. I wonder what the rpm and speed would be with just a driver aboard?

I probably wasn't clear. It will do about 28 WOT with 2 adults and a 3 year old aboard.

 

[steelespike]

Re: Chosing a Better Prop

Ok so basically with 2 aboard, 28 with an indicated 3500.Prop calculator says your actually at about 5100
assuming about 10% slip.I think it should be higher.Going to do a little research.
I couldn't find any definitive Honda tests.
Found a Evinrude test of 2900 lbs With a numerically lower gear ratio 2.00 and a 15" prop
speed was 34 @ 4875. Your ratio is 2.33, easier to turn but results in a little less speed per rpm.
It appears your 15 seems reasonable. Once you confirm your rpm perhaps a 13" will get you some rpm and help getting the heavy load up.Wot light load may be slower with more rpm.
A 13" 4 blade may further improve loaded hole shot.

 

[jestor68]

Re: Chosing a Better Prop

If your tachometer has a plastic connector(plug) on the back, sometimes it helps to pull off the connector and clean the pins.

Over time those pins can get dirty and cause strange readings.

 

[freeltm]

Re: Chosing a Better Prop

Ok so basically with 2 aboard, 28 with an indicated 3500.Prop calculator says your actually at about 5100
assuming about 10% slip.I think it should be higher.Going to do a little research.
I couldn't find any definitive Honda tests.
Found a Evinrude test of 2900 lbs With a numerically lower gear ratio 2.00 and a 15" prop
speed was 34 @ 4875. Your ratio is 2.33, easier to turn but results in a little less speed per rpm.
It appears your 15 seems reasonable. Once you confirm your rpm perhaps a 13" will get you some rpm and help getting the heavy load up.Wot light load may be slower with more rpm.
A 13" 4 blade may further improve loaded hole shot.

Thanks for the advice. I'm going to look into why the tach isn't working right and maybe get a 13" for a spare.