Prop help!!

nitefreak

Cadet
Joined
May 11, 2011
Messages
27
I have a 1982 mercury 80 hp outboard i need help in finding out what the original prop diameter was for this engine. did it come with the 13x19 or 13x17 on it from factory???
 

etracer68

Ensign
Joined
Oct 11, 2009
Messages
906
Re: Prop help!!

Odds are it didnt come with a prop from the factory, unless it was purchased with a boat size in mind. If it were to go on a Pontoon, it may run a 13 pitch, or if a glass 16ft boat maybe a 17 pitch. Need more info, on boat size, and style. The "read this first" in this section is there for a reason. What are you trying to correct, or do.

Also a ,13x17, and a 13x19, are both 13inch diameter props. You would be more interested in the pitch, over the diameter.
 
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moparone

Cadet
Joined
May 4, 2012
Messages
6
Re: Prop help!!

Odds are it didnt come with a prop from the factory, unless it was purchased with a boat size in mind. If it were to go on a Pontoon, it may run a 13 pitch, or if a glass 16ft boat maybe a 17 pitch. Need more info, on boat size, and style. The "read this first" in this section is there for a reason. What are you trying to correct, or do.

Also a ,13x17, and a 13x19, are both 13inch diameter props. You would be more interested in the pitch, over the diameter.

Hello, new at this. We have a 1990 Fisher 240 DLX with A 1990, 90 HP MERCURY. IT'S 24' Long, wieghs about 2400 lbs loaded, the prop is a 13p and all I can get out of it is about 3200 rpm, it runs about 20.5 mph. I've called Tracker and the guy I talked to wasn't much help. Does this sound about right? Just received info on TAP Fins, nice but kind of pricey. Any info would be great. Thanks in advance...
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,290
Re: Prop help!!

Hello, new at this. We have a 1990 Fisher 240 DLX with A 1990, 90 HP MERCURY. IT'S 24' Long, wieghs about 2400 lbs loaded, the prop is a 13p and all I can get out of it is about 3200 rpm, it runs about 20.5 mph. I've called Tracker and the guy I talked to wasn't much help. Does this sound about right? Just received info on TAP Fins, nice but kind of pricey. Any info would be great. Thanks in advance...

Ayuh,.... Welcome Aboard,.... You need to start yer Own thread, 'n not be Hi-jackin' this 1...

Before ya start Yer thread, read the "Read This First" at the top of the forum, so's ya know what Info We need to help ya....
 

nitefreak

Cadet
Joined
May 11, 2011
Messages
27
Re: Prop help!!

The boat is a fiberglass 15ft rinker open bow....The motor currently has a 13x19 prop on it,but im not hitting the recommended WOT rpms. I'm running at 36 mph and 4500 rpm at WOT but the prop does have a little damage on it. My question is do i stick with the 13x19 or should i switch to a 13x17 to try to get closer to my WOT rpm range? Also will i lose or gain any speed by switching to a 13x17? I'm just wanting to replace the damaged prop.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Prop help!!

Near as I can figure your gear ratio is 2.30 at 4500 a 19" prop can't go 36 mph.
Is the speed by gps?
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Prop help!!

Using a 2.30 gear ratio
4500 produces about 31 with a 19" prop. Gps speed would help. Some cells have a gps app.
It is possible you do need a 17" prop but it will only add about 400 rpm.
You may want to confirm the tach.The problem is in this case you normally wouldn't make up 1000 rpm with a prop.
That would put you at about a 14" pitch.close to what a pontoon would need.
So either the numbers are off or the motor is lacking power.
 

doonda61

Cadet
Joined
Mar 23, 2012
Messages
8
Re: Prop help!!

Just a quick note for GPS on phones. Seatow has an app for the iPhone that is free. It has GPS and Compass as well as weather and tide info. Not sure if they have it for the other smart phones. It is handy for GPS speeds if your boat doesn't have one. Also I have a 90TLRA 2 stroke Yamaha, I played with the pitch on the prop by going from a 17 to a 19 and lost RPM and performance. I am no expert by no means, but when I went back to the 17 pitch I regained my WOT RPM and performance came back. My boat is a Duracraft 1860BSBay. If you can borrow a few props in the various pitches you can experiment with your boat and see what gives you the best all around performance. Oh - both props were aluminum
 
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nitefreak

Cadet
Joined
May 11, 2011
Messages
27
Re: Prop help!!

Using a 2.30 gear ratio
4500 produces about 31 with a 19" prop. Gps speed would help. Some cells have a gps app.
It is possible you do need a 17" prop but it will only add about 400 rpm.
You may want to confirm the tach.The problem is in this case you normally wouldn't make up 1000 rpm with a prop.
That would put you at about a 14" pitch.close to what a pontoon would need.
So either the numbers are off or the motor is lacking power.

I have gps on my phone I'll have to check it next time out! Thanks so much for all your help!
 

nitefreak

Cadet
Joined
May 11, 2011
Messages
27
Re: Prop help!!

Just a quick note for GPS on phones. Seatow has an app for the iPhone that is free. It has GPS and Compass as well as weather and tide info. Not sure if they have it for the other smart phones. It is handy for GPS speeds if your boat doesn't have one. Also I have a 90TLRA 2 stroke Yamaha, I played with the pitch on the prop by going from a 17 to a 19 and lost RPM and performance. I am no expert by no means, but when I went back to the 17 pitch I regained my WOT RPM and performance came back. My boat is a Duracraft 1860BSBay. If you can borrow a few props in the various pitches you can experiment with your boat and see what gives you the best all around performance. Oh - both props were aluminum
I'm gonna switch to a 17 pitch I'm sure that's the right one for my boat! Thanks for the advise!
 
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