What Prop Pitch are you guys using on South Park Lakes?
Post By: Sticklips Posted: 5/22/2019 11:16:17 AMPoints: 0
Slightly off topic: Last year, I picked up a 2006 Tracker V18 Allfish with a 115 Mercury 2 cycle Optimax and an OEM 3 blade aluminum prop/19 pitch. The boat weighs 1124 lbs (w/o motor), and figure 450 or so lbs more for 2 guys and gear. The boat was originally operated at or near sea level.
Needless to say, performance on Antero & Spinney was terrible. Max 3000 rpm, 22 mph, hard to get on plane. (makes it tough to wallow back to dock when the wind comes :)
I ran the Mercury Prop Selector Program, and it spit out prop options that were 19 or 17 pitch. On the other hand, a prop distributor recommended 14 pitch. Big difference.
So, some first hand knowledge on what prop spec works for similar boat/motor combinations on South Park lakes would be most helpful.
Reply by: Sticklips Posted: 5/22/2019 11:40:33 AM Points: 0
Yes understand that. Still some uncertainty though when speaking with dealers. I am hoping to hear from a Lund, Tracker, etc owner with a similar Merc who operates successfully at high altitude so I can narrow it down some.
I have a 2000 125 Merc 2ư on an 18' Starcraft Superfisherman. When I first moved here I had a 19 pitch and I had the same problems, even at front range lakes. I switched to a 17 and it fixed my issues. I still have problems at altitudes over 8000 because my motor is carbureted. It has nothing to do with the prop.
Reply by: Ryan Posted: 5/22/2019 6:02:31 PM Points: 1960
That 19 pitch is way too much prop for that boat even on the front range.
What is the WOT RPM on that engine? I would guess around 6000 RPM, so you need to drop significantly.
I would say maybe 15 on the front range and 13 at elevation. The 4 blade suggestion is a good one.
And a carbed engine may be more difficult to start and run at low RPMs at elevation, but it doesn't have much to do with what RPM or speed you are reaching. That is due to the higher elevation. You lose 3% HP for every 1000 foot elevation gain (unless you have forced induction). So that 115 HP engine is about 84 HP in South Park.
Sticklips . . . .when you go up in elevation,you go down in speed.Very simply put,thin air makes your motor less powerful. Most motors up to 1/4 total power up in south park due to less oxygen. This is not to say that you don't need a different pitch prop . . . . .the water's density changes with elevation and that plus the loss of power makes for the different pitch prop.
Reply by: kicker Posted: 5/23/2019 7:12:30 AM Points: 112
My 2 cents. I have a 20 foot Monark with a walk through windshield and a 125 carbed Mercury. You want your wide open throttle RPM's to be as close to max RPM when on plane. I believe that motors wide open throttle RPMs is 5250. like mine. My props are as follows. Lake Powell 19 pitch Chattfield 17 pitch South Park, Grandby, Blue Mesa, Williams Fork, etc. 15 pitch.
Reply by: Dan Swanson Posted: 5/23/2019 8:40:33 AM Points: 1365
The Optimax is a direct injection motor so no re-jetting.
For what itís worth, I ran a 19 pitch high five (5 blade) on a 2007 ProXS 250 on a 20 foot aluminum boat in order to get on plane when I lived at 8000 feet. I ran a 21 3 blade at 5000 feet and went to a 23 3 blade at low altitude (Great Lakes). The 5 blade really helped with holeshot. Yes, talk to a prop shop.
Reply by: malty falcon Posted: 5/23/2019 11:14:41 AM Points: 6199
Hereís my take on yer issue- You are SO far from WOT that it is possibly something other than the prop. Changing the prop's pitch 2Ē will change your RPMs by 400. There are only barge props in 11Ē pitch.
You would need to change the diameter as well as pitch to boost your RPM's by 2250!
Before buying a new and uncertain size of prop, try changing spark plugs and thoroughly inspecting the fuel line and filters to be certain you have good fuel flow. Also confirm spark on every wire- 3000 RPM's max sounds like you may be one or two cylinders short of a full engine.
One other thing you may check is engine height. On plane, your anti-ventilation plate should be breaking the surface. Try to get somebody to look while underway. If it is buried, you can move the motor up one or two holes.
A light boat like yours with a 115 hp engine should still see 30 mph at South Park.
Reply by: Sticklips Posted: 5/26/2019 8:53:48 AM Points: 0
Gentlemen. Thanks for the very informative and helpful suggestions. Aso, I apologize for the late repsonse (I thought I checked "send email when reply received")
Some additional thoughts I have based on the observations:
- Yes, it is a DFI not carb, so re-jeting is not the issue
- Yes, as someone mentioned WOT with the factory 19P on this motor should be 5250 rpm
- Possibility of engine fuel delivery/spark problems. Agreed. Especially, because this motor sat a lot (only 30 hrs). But first, I thought after establishing that 19P wont work at those elevations, wanted to be sure I was running the correct pitch as a baseline, before I started chasing engine issues. Hope that makes sense. Maybe Im apporaching it assbackwards?
- Mercury Prop Selector. It actually does ask for elevation as one of the inputs. I plugged in 8700 ft, and it spit out 19 or 17 pitch. (This contributed to my confusion)
So, in the meantime I did contact an online dealer in WI near Mercury factory figuring they'd know Merc props. 'Boat Propeller Warehouse'. The guys there recommended a Spitfire X7 Four Blade (13.5 x 15 P). This seems to be inline with many of the recommendations here.
So, Im going to swap out props, check fuel fliter, etc. I'll report back here with results
Sorry for the long winded post, but hoping this thread might help others with similar issues on South Park lakes.
Reply by: kicker Posted: 5/26/2019 10:26:54 AM Points: 112
IMO 4 blade props are for hole shots and pulling skiers or tubes etc. 3 blade props for general use. Better top end I believe. I agree 15 pitch as I said. The posts with the higher HP motors will be able to turn a higher pitch prop like a 19.
I had a 17' aluminum boat with 75HP Mercury. When I switched from a 3 blade to 4 blade, it knocked 1.5 MPH off my top end, vastly improved hole shot, and made low speed maneuvering MUCH better. Docking and reverse were SO much easier with 4 blades, vastly better boat control.
When I did it, I believe I reduced the diameter a little bit as well as the pitch. I made the change to get my WOT into the recommended range, same as you, for South Park and Blue Mesa.
Once again, if there are other problems limiting your WOT, changing props won't fix the entire problem.
Reply by: T Haze Posted: 5/27/2019 4:05:10 PM Points: 0
My boat is a 2004 Tracker Targa V-17 with a 2011 115 Merc 4 stroke. My sons boat is a 2011 Tracker PG 17 with a 115 Opti. Both boats are very similar to what you have.
Both of us run a 15p Spitfire. Mine is a stainless X7 and his is aluminum. The Spitfire is specifically made for the 75/90/115 Mercury motors, both four stroke and Optimax. I would not run any other prop on those outboards.
I went from a 15p Black Max 3 blade to the 15p Spitfire X7. I gained about 3 mph and 150 RPM's over the Black Max. At the 8000'+ elevation lakes such as Spinney we both hit about 500 RPM's below the top of the RPM range. On the front range we are really close to the top and at lower altitudes like Powell we are right at the top of the range.
With the Spitfire the old 3 blade versus 4 blade rules go out the window. You won't lose any on the top end and you usually end up with a pretty significant gain in speed. Try it, I would bet you will never look back. My guess is 15 pitch would work for your setup. Your outboard should have the same 2.07 lower unit gearing as ours.
A big thing I left out that....You should try to locate Ethanol Free fuel - it makes a huge difference in the power of your outboard. The Conoco in Divide sells it or you can check out the website pure-gas.org. If you want to run 87 Octane instead of 91....the Murphy Gas stations in the Springs sell 87 Octane Ethanol Free. My buddy's 16' Tracker with a 40 hp Mercury wouldn't get on plane until he changed to Ethanol Free fuel.
I have an 18.5 Crestliner Sportfish with a 115hp Johnson (both 2000 year models). I was told by the Johnson tech locally to prop it for 5000RPMs at WOT. I dropped from a 19 pitch to a 17 pitch and I just get to 5000 rpms and about 31mph at Spinney. It gets out of the hole reasonably well and planes out at less than half throttle. I can troll al day at idle and then whack the throttle open and go.
I had a 19 degree when I bought my boat with a 90 hp EFI 4 stroke. Talked both with local dealer and talked directly to Mercury. Switched to a 17 degree and now get between 5000 and 6000 rpm (32 mph) and a smooth ride with good planning on both Spinney and Antero. Mercury engineer took great time to explain and how to use their prop guide. My boat is a 16.5 ft. Alumacraft deep V Navigator.