New Boat needs a Prop

[rned]

I purchased a 2000 Starcraft 17'6 " Aluminum Super Fishernan. It has a 2000 Mercury 90 HP. I used the boat for the first time and Prop seems way off. The WOT RPMs are almot 6,000. When you pull out, the RPMs go to max and you just trim the engine to get the speed.

The prop is a 13.25 x 17. I was going to go to a 13 x 19 Solas. Any recommendations? I have read that a 4 blade gives a better bottom end but less top speed. I am not interested in top speed, how much top speed do you loose when you go to a 4 blade?

What 4 blade would be equal to 3 blade 13 x 19?

Thanks

rned

 

[marcortez]

Re: New Boat needs a Prop

Try this easy to use calculator.

http://appcenter.mercurymarine.com/propSelector/home.do

 

[hwsiii]

Re: New Boat needs a Prop

rned, I need to know the factory recommended MAX RPM and the gear ratio of your motor, as well as your max speed by GPS and RPM at WOT.



H

 

[rned]

Re: New Boat needs a Prop

Appreciate the help. Due to the weather it will be a few days until I can get it on the water. I will take along my GPS and check the speed and get back to you.

Thanks again
rned

 

[hwsiii]

Re: New Boat needs a Prop

I will be waiting.



H

 

[rned]

Re: New Boat needs a Prop

H,'

I just got back from the lake. My tach goes to 6,000 and the boat was at 6 or just a bit over 6,000. The peed on the GPS was 39 MPH. I couldn,t find the ratio in my manual but I fond it on a prop web site, 2.30:1. RPM rang for the outboard is 5,000 to 5,500. I was told some engines have a rev limiter. I may hve been at the redline

I also took a reading at 5,000 and the speed was 32.7. The motor is a 2000 Mercury 2 cycle 90 hp.

I was doing some reading on props and ws thinking of a TP Legacy. Any comments? I cant run a SS prop. I go to Canada fishing and am afraid of hitting rocks.
One more thing, the outboard cold possibly be moved up one hole. The cavitation is about even with teh bottom of the deep V.


I am not looking for top end. I would like to cruse around 30 and keep the rpms below the max.

Thanks

 

[hwsiii]

Re: New Boat needs a Prop

Rned, the make and model of prop you have right now is doing very good and only showing a prop slip of 7%, which is excellent.

Prop Slip

IF you will move the motor up two notches and buy a 19" pitch Legacy prop you will be able to cruise over 30 MPH at about 4,100 RPM with a max RPM of about 5,500 RPM and about 3 MPH more top speed.

You might try reading this for a better understanding of changing props for better performance, and for the major differences between aluminum props and stainless steel.

http://forums.iboats.com/showthread.php?t=369057



H

 

[rned]

Re: New Boat needs a Prop

H, I appreciate allof your help. The other aricle was also helpful. I noticed you mentioned teh Solas Prop. That was going to be my first coiuce and then I found sopme articles on teh TP Legacy with the exhaust vent hole. I was on the TP web site and got the impression that their aluminum props have more engineering and design than typicl aluminum props, and they were more like a SS design. The Solas doesn't have the vent hole but has the better casting process thai I like.

Would I be better off going to a Solas 4 blade?

If you were in my position, what would you do?

I have always run SS props in the past. Now that I boat in Canada and would like to go to the 1000 Islands, I feel I need to use aluminum.

 

[hwsiii]

Re: New Boat needs a Prop

Ned, I am not real high on the TP props, because I have seen people make changes to them and then the RPM are way off. BUT your boat is doing fine with the normal props you have now as far as prop slip, and I do believe that the legacy will let you move your motor up more and give you extra speed with very little prop slip, so I believe the Legacy will be better for your particular uses.



H

 

[rned]

Re: New Boat needs a Prop

Done, I will purchase the Legacy and let you know how I make out. Thanks again.

Ron

 

[hwsiii]

Re: New Boat needs a Prop

Ron, I will be ehere waiting for the results.



H

 

[rned]

Re: New Boat needs a Prop

H,

I ran the new TP Legay prop tonight and these are the results
5,950 rpm and 40.3
5,00 rpm and 33.5

I could just about reach 6,000 rpm. I did not raise the motor. I wanted to make one change at a time and test it. I did notice the at WOT there was a fair amount of water over the top of the cavitation plate. I am going to lift the motor and see what that does.

The boat steers hard unless the have the trim just perfect. Should raisig the motor help with that?

I will rais the motor this week and run it again over the weekend.

I like the TP Legacy prop. It feels like it has more bite and if you cavitate in the turn and lower the trim it bites and pulls right away.

Thanks
Ron

 

[hwsiii]

Re: New Boat needs a Prop

Rned,

The prop is a 13.25 x 17

Old Prop

My tach goes to 6,000 and the boat was at 6 or just a bit over 6,000. The peed on the GPS was 39 MPH.I also took a reading at 5,000 and the speed was 32.7

H

IF you will move the motor up two notches and buy a 19" pitch Legacy prop you will be able to cruise over 30 MPH at about 4,100 RPM with a max RPM of about 5,500 RPM and about 3 MPH more top speed.Ned, I am not real high on the TP props, because I have seen people make changes to them and then the RPM are way off.

Rned

I ran the new TP Legay prop tonight and these are the results
5,950 rpm and 40.3
5,00 rpm and 33.5

Did you buy the Legacy in the 19" pitch or the 17" pitch, because the 19" should have lowered the RPM by about 400 or 500 RPM and raised the speed more, that is what we were trying to accomplish. We are right at the same speeds and RPM that we were before we got the new prop and we should not be.

Rned

The boat steers hard unless the have the trim just perfect.

You need to adjust the trim tab(anode) right above the prop, if the boat is trying to pull to the right and you have to steer hard to the left to stop that you need to move the back of the anode to the left to compensate for that pull, then just tighten the trim tab back up.



H

 

[rned]

Re: New Boat needs a Prop

H

In my first test the WOT was over 6,000, maxed on my tach and speed was 39. My RPMs now max at 5,900 and my speed is 40.3 that is 1.3 mph increase and a drop in rpms, not certain because I was maxed out on the tach.

At 5,000 rpm I was 32.7 on the old prop and 33.5 mph on the new prop

Since I have not raised the motor and the cavitation plate is even with the bottom of the v in the hull, could I not be gainig the max benefit of the prop?

I did purchase a Legacy 13 x 19 prop. The boat steers hard in both directions unless you trim it just right. Would that be the trim tab?

Thanks
Ron

 

[86 century]

Re: New Boat needs a Prop

Ron lets see some pics of that starcraft and we can properly welcome you to our little cult/club. You will find alot of SC nuts on this site and if you would let us Know were you are from.

 

[hwsiii]

Re: New Boat needs a Prop

Ron, is that a 2 stroke or a 4 stroke motor.



H

 

[rned]

Re: New Boat needs a Prop

H

The motor is a 2 stroke.

Thanks

Ron

 

[rned]

Re: New Boat needs a Prop

I will raise my engine this week and will let you know if it makes a difference.

Thanks for your help

Ron

 

[hwsiii]

Re: New Boat needs a Prop

Ron,

I was told some engines have a rev limiter. I may hve been at the redline

You need to send that prop to Turning Point and have them trade it for a 21" pitch. I assume that you were redlining the first time you gave me the WOT RPM and speed with the old prop, thus your motor was capable of turning more RPM than it showed. They will gladly trade the prop out at no charge, so long as it looks like it should, but you need to call them to get a Return Authorization Number.

By doing this we will gain a little more speed and get your RPM back down to where they ought to be, and then we can raise the motor up for maximum speed.



H