What prop would work best

[poncho206]

Hi,
I have a 2007 Riverhawk 160lh with a 60hp mercury 4stroke outboard weight without people is about 1600lbs. My current prop is 10.38 X 14p 3 blade and my gear ratio is 1.83:1 my wot is 5500 to 6000. My top speed by my self is about 32mph at 5500rpms. The problem I have is when I get 4 of us in the boat, than my top speed is about 12mph and I can't get the rpms above 5000 rpms and I don't get on plane, total people weight is about 800lbs. My goal is 20+ mph and being able to get on plane. I also have a hydrofoil on the motor. I'm looking for a prop al. or s.s. 3blade or 4blade that would help reach my goal in the recommended rpm range.
Thank you for any information.
Frank

 

[Starcraft5834]

Re: What prop would work best

4 blade will increase your thrust and should get you on plane faster with a load.. ... you say alone, your at 32 at 5500,, now with a load at 12 and plowing through the water with current prop,, I'm pretty certain a 4 blade will get you out of the hole and near the #'s you want.. .others are experts relating to recommended pitch.. I would suggest you look at 4 blade an increase pitch a bit......... others will chime in...

 

[SkiDad]

Re: What prop would work best

i would drop down 2 pitches in prop - use a 12 pitch to get your rpm to 6000 with just you in there.

check this test out: Engine Test | Mercury Marine

 

[steelespike]

Re: What prop would work best

I agree I think a change to a 12" pitch will help a lot.
If I can believe the Riverhawk site the boat is rated for 135 hp.If so then your pretty badly underpowered.
It is usually suggested to have 2/3 to 3/4 of the rated hp.
Your foil probably helps get on plane but could be eating up some top speed and may cause strange handling
at speed.The boat may seem like it is stuck to the water.

 

[poncho206]

Re: What prop would work best

When I bought it in 2007 they only rated it at 90hp, which is strange the new one are rated 135hp and about 400lbs more capacity, but the dimensional specs are the same. I was wondering about using a 4 bladed prop, but what diameter and pitch would be good and on the 3 blade 12 pitch would that be the same diameter?

 

[poncho206]

Re: What prop would work best

Ok I just ordered a Solas Amita 4 Blade Aluminum 11.13" dia. X 11" from here. I'll post result after my next fishing trip.

 

[steelespike]

Re: What prop would work best

delete.

 

[steelespike]

Re: What prop would work best

The 11" may be overkill but should be like a new motor probably jump out of the hole like a rocket.
It may over rev but you can just throttle back a little.
The 4 blade should help hole shot, stay on plane at reduced throttle with less fiddling and respond better around the dock.
With luck wot should produce about 31 at 6000,.assuming about 8% slip.

 

[poncho206]

Re: What prop would work best

I went with the 11" because it said to drop 1 extra inch when switching from a 3 blade to a 4 blade and this prop is almost a full inch larger diameter. Plus top speed has never been a factor, if I can get 20mph and on plane with a full boat I will be very happy. When I go out alone I can always switch props.

 

[dazk14]

Re: What prop would work best

Are you currently using a Solas prop? Interested in your results data.
The 11" 4 blade should do quite well loaded.

 

[poncho206]

Re: What prop would work best

I got the prop on my boat but I haven't had a chance to take my boat out yet. I'm taking my boat out to tomales bay this weekend, but the test won't be exactly right. One guy can't make it so I'll be about 250 lbs less, but I should still see a big difference.

 

[poncho206]

Re: What prop would work best

Well I got the boat out Saturday, now we were about 200 lbs lighter than than my last trip. Heres the results it jumped on plane with in a few seconds and I was hitting just below 27 mph at 5800 rpms, at idle the boats going 2.5 mph, all speeds are gps. I'm very happy with these results