Need help on prop size.

[Robs88]

Hey guys i got a 1994 Angler 170 CC that i just rigged with a 1997 Mercury 115hp, The motor came with a 17p SS prop, I thought the boat was going perform really well as its a light hull, Well took it out yesturday and was disappoint, She shoots outta the hole crazy fast, but W.O.T. was 34mph on gps, This is at 5300rpm and motor trim down. Can anyone help choose a right prop or help me out.

 

[Snowfish]

Re: Need help on prop size.

Assuming that you had to back out of it to keep from over reving, I think you'll love a 21 pitch on your rig. Not apples to apples, but I run a 21 pitch on my 18ft StarCraft Bowrider 120hp I/O(profile pic) 40mph @ 4100rpm. Nice! I put my 17 pitch on to take the kids wakeboarding though. I call it my stump puller prop.

 

[hwsiii]

Re: Need help on prop size.

Rob, that motor is only supposed to to turn about 5,250 RPM and it has a 2.07:1 gear ratio, please verify this. I also notied you said 34 MPH was with the drive trimmed in not out. Trim it out till it you hear it ventilating and you get no more speed inrease then trim in until it quits ventilating and that is your best RPM and speed. Trimmed in the speed an be 5 MPH less than trimmed out.


H

 

[Robs88]

Re: Need help on prop size.

Rob, that motor is only supposed to to turn about 5,250 RPM and it has a 2.07:1 gear ratio, please verify this. I also notied you said 34 MPH was with the drive trimmed in not out. Trim it out till it you hear it ventilating and you get no more speed inrease then trim in until it quits ventilating and that is your best RPM and speed. Trimmed in the speed an be 5 MPH less than trimmed out.


H

Yes hwsiii your correct 4750-5250 rpms, I had motor trim down cause, the she porpoise really bad when trimmed up too much, Yes im looking for a prop that can give me good midrange and very good top end speed. I really dont mind the hole shot to much. I wanna cruise at 4100 rpms at bout 32-33 mph and toping out at around 45-48, but still stay in the engine's rpm range. Any suggestion will be appreciated.

 

[Robs88]

Re: Need help on prop size.

Assuming that you had to back out of it to keep from over reving, I think you'll love a 21 pitch on your rig. Not apples to apples, but I run a 21 pitch on my 18ft StarCraft Bowrider 120hp I/O(profile pic) 40mph @ 4100rpm. Nice! I put my 17 pitch on to take the kids wakeboarding though. I call it my stump puller prop.

Good to know snowfish, but dont know if ill stay within engine rpm range with a 21p, Maybe im wrong though ...

 

[hwsiii]

Re: Need help on prop size.

May I ask what motor you plan on using to reah 48 MPH.


H

 

[Robs88]

Re: Need help on prop size.

May I ask what motor you plan on using to reah 48 MPH.


H

My Mercury 115hp =-)

 

[hwsiii]

Re: Need help on prop size.

Ok


H

 

[Robs88]

Re: Need help on prop size.

Ok


H

So you have any recommendation.

 

[hwsiii]

Re: Need help on prop size.

If you will fill this out I will run the numbers and see what they say.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape a c ross the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a Tiny Tach for $ 50
RPM ___________ Speed ___________ No. of people ____________ Gas ________
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.


H

 

[Robs88]

Re: Need help on prop size.

If you will fill this out I will run the numbers and see what they say.

Iboats Boat and Motor Info

1. Year, make and model of boat
1994 Angler 170 CC
2. Length, width and base weight of boat, look for boat decal on back of boat
17ft 7'2" width base weight 1,170 lbs
2a.What is the maximum recommended HP for your boat
90hp
3. Number of people and gallons of gas normally on boat
Me and 2 passengers 25 gallons of fuel
4. What do you use the boat for
Crusing and Fishing
5. Is it a Deep Vee and if so how many degrees of deadrise
Nope
6. Year, make. manufacturer and model of motor
1997 Mercury 115hp ELPTO 2+2
7. HP and gear ratio of motor IMPORTANT
115hp 2.07:1
If you don?t know the ratio, you need to pull the plugs out and put a piece
of tape a c ross the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
4750--5250 rpms
9. Anti-ventilation Plate height above keel of boat if it is an outboard in
inches, use a board under the keel and stiking out to the anti ventilation
plate for a referene
Not sure
10. Is it a bass boat or does it have a pad bottom
Not a bass boat
11. Does it have a hydrafoil, dolefin or trim tabs
nope
12. Make, model, diameter, pitch and whether SS or aluminum prop
Quicksilver prop# 48-72764A4 17p 13-1/4 x 17
13. WOT RPM and speed from your current prop and how much gas and how
many people were in the boat for the test data and is the speed by GPS.
5300rpms 34mph one passenger 16 gallons of fuel speed by gps
Make sure you trim the prop up until it starts ventilating and then just trim in
Engine trim down.
until it quits ventilating. If you do not have a tach you can buy a Tiny Tach for $ 50
RPM ___________ Speed ___________ No. of people ____________ Gas ________
14. Are you at sea level or a higher elevation, give us the elevation in feet
Sea level
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
yes april 9th full service
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
Dont know just bought engine
17. Does the prop show any damage that you can see
Nope
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
Faster midrange and higher top end speed to conserve fuel.
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.


H

Hope this helps.. lmk thanks!

 

[hwsiii]

Re: Need help on prop size.

Rob, I am showing you have a prop slip of 18% right now and I believe that is aused by you having the motor trimmed all the way in at WOT. You need to take it out again and trim the motor up and get some new numbers. But at this time I show you an probably get about 40 MPH maximum speed at WOT. I will reommend a prop after we see if we an get your prop slip down by trimming the motor up. Try putting someone in the bow to stop the porpoising or move them to the stern.


H

 

[Robs88]

Re: Need help on prop size.

Rob, I am showing you have a prop slip of 18% right now and I believe that is aused by you having the motor trimmed all the way in at WOT. You need to take it out again and trim the motor up and get some new numbers. But at this time I show you an probably get about 40 MPH maximum speed at WOT. I will reommend a prop after we see if we an get your prop slip down by trimming the motor up. Try putting someone in the bow to stop the porpoising or move them to the stern.


H

Will do Hwsiii, Taking her out again on the weekend, will bump the thread with the new results, with engine trimmed up.

 

[hwsiii]

Re: Need help on prop size.

That sounds great Rob.


H