Anonymous
01-21-2003, 10:48 PM
Prior Engagement
normal member in standard member. 1. Another Prop Question
I posted this response and question under the "How Fast?" thread, but decided to copy it over here which is more appropriate. So, here it is:
I have a 2000 246 W/A with 300 HP TBI and 16x16 prop. Paperwork that can with the boat says 16x17. However, upon inspection of the prop, the 17 was stamped out and another 16 stamped in its place. Boat cruises 20 kts at 2,950-3,000 rpm. WOT is approximately 4,800-5,000. Can't remember the actual speed. I believe around 32-34 knots (according to the tri-ducer paddlewheel for fish finder).
I have been considering changing prop to get more mid-range speed, to increase my MPG. I feel that the 300 ponies is more than enough for the boat even fully loaded, however, there has been lots of discussion regarding over propping and how bad it is on engines and transmissions.
I see in the 2001 catalog that boats are shown with four blade props. Does anyone know if they (the Boats) are coming standard with these? There is a local guy here in Richmond that can probably happen the tech side of it. I am considering going four blade and an appropriate increase in size and pitch (after converting for change from three to four blades). Any comments or suggestions form the board?
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 06:06 p.m. on 01-22-2001
green o
normal member in standard member. 2. Re:Another Prop Question
I am going through the same thing with my 22 wac. Everybody has a different opinion on the subject. I called Michigan Wheel Corp.Go to their web site at www.miwheel.com and fill out form with all your boat & motor info. They will tell you what size prop you need in 3-5 days. I did not receive my answer yet but will let you know what they said. Let me know how you make out. Good luck Tom G.
Date: 02:04 p.m. on 01-23-2001
chuckash
normal member in standard member. 3. Re:Another Prop Question
I posted the "How Fast" question because we converted from a 302 2 bbl to a 351 4 bbl and wondered if our results were typical.
Anway, when we first did this motor swap, the motor way over-revved with the original prop (12x13). I also contacted Michigan and they made a recommendation. It has alway been my understanding, though, that the boat should be propped to run at WOT at whatever RPM the peak torque occurred. The motor manufacturer should also specify the RPM's at which the motor should run WOT, try contacting them. It took a few tries, but we finally settled in on a prop that had more pitch and was also cupped (actually it was the original prop that was reconditioned locally). The cupping really helped pull the boat out of the hole, while also increasing fuel economy.
We can run 20 minutes to the inlet (10 miles), 18 miles out, troll for several hours and make the return trip all on about 25 gallons of fuel. Can't argue with that success.
Date: 08:00 p.m. on 01-23-2001
Leprechaun
premium member in standard member. 4. Re:Another Prop Question
Mike/Prior E - go to this site - cut and paste into your browser) and look what my friend Thom (From yet ANOTHER post board) has written on the subject. A long/worthwhile read.
http://www.boatered.com/topic.asp?topic_id=7092&forum_id=3&Topic_Title=re%2Dprop+%
Regards, Leprechaun
Date: 08:37 p.m. on 01-23-2001
Prior Engagement
premium member in standard member. 5. Re:Another Prop Question
Lep,
Wow! Thanks for the link. Good stuff there. I'll digest all of this info (printed it out for future reference). I need to get hard data on the speed at cruise and WOT along with RPM's. Do you have any personnel suggestions?
Any other info and ideas are appreciated.
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 10:29 p.m. on 01-23-2001
Leprechaun
premium member in standard member. 6. Re:Re:Another Prop Question
Yep - my suggestion is to stick with the prop that's on there. The numbers seem right ot me. Going to a 4-blade is an in-exact science at best, regardless of what the manufacturers and prop-shops say. The common sentiment is to decrease pitch by one inch and maintain diameter, but these Shamrocks are so funky in thier response to prop changes, who knows what's right? My dock buddy and mentor tried to swap his 16X17 3-blade for a 16X16 4-blade on his 26 Pilothouse and the boat went slower on top, cruise gph fuel burn went up and the boat sounded like a helicopter at all speeds. He'll give me that $500 prop for free and I don't want it.
Not even for free.
It's the natural inclination of a boat owner to tinker, trying to optimize our equipment, this one time I think no amount of tinkering will help. It WILL however make your wallet significantly lighter.
Our Board Host, Gavin has the same rig as you do. Maybe he can look under his boat and tell us what prop is on there and the performance characteristics of the boat. Gavin . . . you out there? Regards, Leprechaun
Date: 09:55 a.m. on 01-24-2001
normal member in standard member. 1. Another Prop Question
I posted this response and question under the "How Fast?" thread, but decided to copy it over here which is more appropriate. So, here it is:
I have a 2000 246 W/A with 300 HP TBI and 16x16 prop. Paperwork that can with the boat says 16x17. However, upon inspection of the prop, the 17 was stamped out and another 16 stamped in its place. Boat cruises 20 kts at 2,950-3,000 rpm. WOT is approximately 4,800-5,000. Can't remember the actual speed. I believe around 32-34 knots (according to the tri-ducer paddlewheel for fish finder).
I have been considering changing prop to get more mid-range speed, to increase my MPG. I feel that the 300 ponies is more than enough for the boat even fully loaded, however, there has been lots of discussion regarding over propping and how bad it is on engines and transmissions.
I see in the 2001 catalog that boats are shown with four blade props. Does anyone know if they (the Boats) are coming standard with these? There is a local guy here in Richmond that can probably happen the tech side of it. I am considering going four blade and an appropriate increase in size and pitch (after converting for change from three to four blades). Any comments or suggestions form the board?
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 06:06 p.m. on 01-22-2001
green o
normal member in standard member. 2. Re:Another Prop Question
I am going through the same thing with my 22 wac. Everybody has a different opinion on the subject. I called Michigan Wheel Corp.Go to their web site at www.miwheel.com and fill out form with all your boat & motor info. They will tell you what size prop you need in 3-5 days. I did not receive my answer yet but will let you know what they said. Let me know how you make out. Good luck Tom G.
Date: 02:04 p.m. on 01-23-2001
chuckash
normal member in standard member. 3. Re:Another Prop Question
I posted the "How Fast" question because we converted from a 302 2 bbl to a 351 4 bbl and wondered if our results were typical.
Anway, when we first did this motor swap, the motor way over-revved with the original prop (12x13). I also contacted Michigan and they made a recommendation. It has alway been my understanding, though, that the boat should be propped to run at WOT at whatever RPM the peak torque occurred. The motor manufacturer should also specify the RPM's at which the motor should run WOT, try contacting them. It took a few tries, but we finally settled in on a prop that had more pitch and was also cupped (actually it was the original prop that was reconditioned locally). The cupping really helped pull the boat out of the hole, while also increasing fuel economy.
We can run 20 minutes to the inlet (10 miles), 18 miles out, troll for several hours and make the return trip all on about 25 gallons of fuel. Can't argue with that success.
Date: 08:00 p.m. on 01-23-2001
Leprechaun
premium member in standard member. 4. Re:Another Prop Question
Mike/Prior E - go to this site - cut and paste into your browser) and look what my friend Thom (From yet ANOTHER post board) has written on the subject. A long/worthwhile read.
http://www.boatered.com/topic.asp?topic_id=7092&forum_id=3&Topic_Title=re%2Dprop+%
Regards, Leprechaun
Date: 08:37 p.m. on 01-23-2001
Prior Engagement
premium member in standard member. 5. Re:Another Prop Question
Lep,
Wow! Thanks for the link. Good stuff there. I'll digest all of this info (printed it out for future reference). I need to get hard data on the speed at cruise and WOT along with RPM's. Do you have any personnel suggestions?
Any other info and ideas are appreciated.
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 10:29 p.m. on 01-23-2001
Leprechaun
premium member in standard member. 6. Re:Re:Another Prop Question
Yep - my suggestion is to stick with the prop that's on there. The numbers seem right ot me. Going to a 4-blade is an in-exact science at best, regardless of what the manufacturers and prop-shops say. The common sentiment is to decrease pitch by one inch and maintain diameter, but these Shamrocks are so funky in thier response to prop changes, who knows what's right? My dock buddy and mentor tried to swap his 16X17 3-blade for a 16X16 4-blade on his 26 Pilothouse and the boat went slower on top, cruise gph fuel burn went up and the boat sounded like a helicopter at all speeds. He'll give me that $500 prop for free and I don't want it.
Not even for free.
It's the natural inclination of a boat owner to tinker, trying to optimize our equipment, this one time I think no amount of tinkering will help. It WILL however make your wallet significantly lighter.
Our Board Host, Gavin has the same rig as you do. Maybe he can look under his boat and tell us what prop is on there and the performance characteristics of the boat. Gavin . . . you out there? Regards, Leprechaun
Date: 09:55 a.m. on 01-24-2001