Prop sizes

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AnglersPursuit
Posts: 63
Joined: Wed Mar 02, 2016 10:26 am

Prop sizes

Post by AnglersPursuit »

Bought a new boat/motor and recently had motor issues unrelated to the prop. The new tech looking at it happens to tell me my prop is too small at 13x19 and should be x21. Says I’ve been over 6100rpms for over 2 hours of run time. Manufacturer says motor shipped with x21.

I understand the short term performance issues the smaller prop can have but any long term issues from this as well?

Should the manufacturer send me the right prop or keep rolling with what the dealer put on?
monte300
Posts: 957
Joined: Thu Mar 02, 2017 12:18 pm
Location: San Ramon

Re: Prop sizes

Post by monte300 »

How long is your boat and what engine horsepower? My 2000 Triton TR19 (18'11") with a 175 Evinrude came with a four blade 25 pitch. I had some issues with chine walking and I wanted a better holeshot and midrange, so I had it worked down to a 23 pitch. Best decision I ever made.
AnglersPursuit
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Joined: Wed Mar 02, 2016 10:26 am

Re: Prop sizes

Post by AnglersPursuit »

19’ with a 115hp. Boat is aluminum.
monte300
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Joined: Thu Mar 02, 2017 12:18 pm
Location: San Ramon

Re: Prop sizes

Post by monte300 »

AnglersPursuit wrote:19’ with a 115hp. Boat is aluminum.
19 or 21 sound reasonable to me, but I'm no expert. Check the operating range of your engine to determine if 6100 RMP's is considered high. I will defer to more knowledgeable folks on this board regarding the best prop for your setup.
AnglersPursuit
Posts: 63
Joined: Wed Mar 02, 2016 10:26 am

Re: Prop sizes

Post by AnglersPursuit »

Right on and thank you! Can’t imagine I’ll be running WOT too often these days so not sure if the change will make a difference. Maybe it lowers the RPM’s at the lower speeds too?


Thanks again!
WRB
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Location: Simi Valley

Re: Prop sizes

Post by WRB »

Depends on a lot of factors, altitude you operate your boat, load and weight distribution you normally run with like 2 anglers, livewell full of water (8 lbs per gallon) and gasoline weight (6.5 lbs per gallon, number and size of batteries etc, etc.
5,800 Rpm at WOT is average for today's 2 cycle OB's.
If you are happy with the hole shot or time to get up on plane and top end speed at 5,800 rpm's keep what you have. 6,100 rpm's is adding wear on your engine.
A 3 blade 20 pitch SST prop will give you better overall performance and drop the rpm's about 300, the 3 blade 21" pitch faster top end speed if the engine can rev to 5,800.
If the dealer changed the factory 21"P SST prop to a aluminum 19" pitch you were had and they owe you a prop.
Tom
HappyDogBassFishing
Posts: 61
Joined: Wed Apr 17, 2019 5:44 am

Re: Prop sizes

Post by HappyDogBassFishing »

My boat is the same, 115hp motor on a tracker 190. Mine came with a 23p. I switched to a 21p and like it a lot more. 19 is undersized for that motor. When I switched I got higher rpms. So you will get lower rpms moving from a 19 to a 21. I hope that helps.
AnglersPursuit
Posts: 63
Joined: Wed Mar 02, 2016 10:26 am

Re: Prop sizes

Post by AnglersPursuit »

WRB wrote:Depends on a lot of factors, altitude you operate your boat, load and weight distribution you normally run with like 2 anglers, livewell full of water (8 lbs per gallon) and gasoline weight (6.5 lbs per gallon, number and size of batteries etc, etc.
5,800 Rpm at WOT is average for today's 2 cycle OB's.
If you are happy with the hole shot or time to get up on plane and top end speed at 5,800 rpm's keep what you have. 6,100 rpm's is adding wear on your engine.
A 3 blade 20 pitch SST prop will give you better overall performance and drop the rpm's about 300, the 3 blade 21" pitch faster top end speed if the engine can rev to 5,800.
If the dealer changed the factory 21"P SST prop to a aluminum 19" pitch you were had and they owe you a prop.
Tom
Definitely installed a 19" aluminum prop. Was told when I picked up boat motor was sent without prop so they put that one on. When you say "had", you think this was done intentionally?

So the 19 is ok, just don't run it WOT?
AnglersPursuit
Posts: 63
Joined: Wed Mar 02, 2016 10:26 am

Re: Prop sizes

Post by AnglersPursuit »

HappyDogBassFishing wrote:My boat is the same, 115hp motor on a tracker 190. Mine came with a 23p. I switched to a 21p and like it a lot more. 19 is undersized for that motor. When I switched I got higher rpms. So you will get lower rpms moving from a 19 to a 21. I hope that helps.
Definitely helps. Thank you!

As a new boat owner I trusted the boat brand and dealer to help me understand my investment. Finding out it's been the opposite. No idea why a 19 was put on there.
HappyDogBassFishing
Posts: 61
Joined: Wed Apr 17, 2019 5:44 am

Re: Prop sizes

Post by HappyDogBassFishing »

You can get a Black max 21p (for Merc outboards) on Amazon for $160. Keep the 19 on the boat as a back-up. Good luck.
WRB
Posts: 1069
Joined: Tue Dec 29, 2015 8:47 pm
Location: Simi Valley

Re: Prop sizes

Post by WRB »

AnglersPursuit wrote:
WRB wrote:Depends on a lot of factors, altitude you operate your boat, load and weight distribution you normally run with like 2 anglers, livewell full of water (8 lbs per gallon) and gasoline weight (6.5 lbs per gallon, number and size of batteries etc, etc.
5,800 Rpm at WOT is average for today's 2 cycle OB's.
If you are happy with the hole shot or time to get up on plane and top end speed at 5,800 rpm's keep what you have. 6,100 rpm's is adding wear on your engine.
A 3 blade 20 pitch SST prop will give you better overall performance and drop the rpm's about 300, the 3 blade 21" pitch faster top end speed if the engine can rev to 5,800.
If the dealer changed the factory 21"P SST prop to a aluminum 19" pitch you were had and they owe you a prop.
Tom
Definitely installed a 19" aluminum prop. Was told when I picked up boat motor was sent without prop so they put that one on. When you say "had", you think this was done intentionally?

So the 19 is ok, just don't run it WOT?
Merc Optimax 115 hp is shipped with a aluminum prop as standard equipment. The Laser II 20 pitch SST prop is ideal for this engine if the aluminum 19 P is turning 6100 rpm's, the 20 P should drop down to 5800. Aluminum props flex SST props don't. As noted the aluminum makes a good back up prop. Someone changed the prop or the engine was shipped with a 19 P aluminum.
It's your boat, but I wouldn't run at 6100 rpm's and it's hard not to when under propped.
Tom
milehi
Posts: 304
Joined: Wed Apr 29, 2009 4:32 pm

Re: Prop sizes

Post by milehi »

I have an old 18' champion with an '04 115 merc. Fish only at 5000'+ Came with a 19, sound right?
AnglersPursuit
Posts: 63
Joined: Wed Mar 02, 2016 10:26 am

Re: Prop sizes

Post by AnglersPursuit »

WRB wrote:
AnglersPursuit wrote:
WRB wrote:Depends on a lot of factors, altitude you operate your boat, load and weight distribution you normally run with like 2 anglers, livewell full of water (8 lbs per gallon) and gasoline weight (6.5 lbs per gallon, number and size of batteries etc, etc.
5,800 Rpm at WOT is average for today's 2 cycle OB's.
If you are happy with the hole shot or time to get up on plane and top end speed at 5,800 rpm's keep what you have. 6,100 rpm's is adding wear on your engine.
A 3 blade 20 pitch SST prop will give you better overall performance and drop the rpm's about 300, the 3 blade 21" pitch faster top end speed if the engine can rev to 5,800.
If the dealer changed the factory 21"P SST prop to a aluminum 19" pitch you were had and they owe you a prop.
Tom
Definitely installed a 19" aluminum prop. Was told when I picked up boat motor was sent without prop so they put that one on. When you say "had", you think this was done intentionally?

So the 19 is ok, just don't run it WOT?
Merc Optimax 115 hp is shipped with a aluminum prop as standard equipment. The Laser II 20 pitch SST prop is ideal for this engine if the aluminum 19 P is turning 6100 rpm's, the 20 P should drop down to 5800. Aluminum props flex SST props don't. As noted the aluminum makes a good back up prop. Someone changed the prop or the engine was shipped with a 19 P aluminum.
It's your boat, but I wouldn't run at 6100 rpm's and it's hard not to when under propped.
Tom
Pretty much what I’m hearing from others is boat is under propped. Manufacturer of boat said motor was shipped with 21”. Wether it was or wasn’t, a 19” shouldn’t have been put on.

Got a top notch mech working on it now. Good people will get me squared away. Thanks for the feedback!
Rod Martin
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Joined: Sat May 07, 2005 6:31 pm
Location: Holiday,Fl.

Re: Prop sizes

Post by Rod Martin »

The Mercury Spitfire X7 is built for the 75-115 class motor . If changing props I would take a look at it.

The Spitfire is Aluminum, The SpitfireX7 is an Alloy
TR177 Ranger/ Mercury/Lowrance/ Ghost TM
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