2015 Mercury 20 HP

junkman41

Petty Officer 1st Class
Joined
Oct 16, 2011
Messages
350
I have a 20 HP four stroke, with a 10P prop on it, the motor is mounted on a Alumacraft 16.5 boat. I was hoping that someone can tell me if I can put another prop on the motor so I can get more speed. and what pitch would do the job without over killing the motor
thank you
Jack
 
Last edited:

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
We need your lightly loaded wot rpm and gps speed.You will need a tach to tell if there is room for a change and the results of any change.
Is the boat bare bones, no floor,casting deck or live well,
 

junkman41

Petty Officer 1st Class
Joined
Oct 16, 2011
Messages
350
I don't know what the wot is I don't have a tach, the boat is loaded it has a floor a casting deck livewell, me at 300 lbs, it just seems to me that I should be able to get more speed out of this motor, I was thinking a high thrust prop, but not sure of the pitch
thank you
 
Last edited:

Bill kubiak

Chief Petty Officer
Joined
Jan 31, 2004
Messages
629
Most of those pontoon boats that I have seen have those hi thrust Micky Mouse ears type of props on them to power those rigs along at a steady speed, pontoons do not go fast, is your prop a three or four blade. It looks like you have a pretty large boat and Judging your boat by the picture a 20 hp seems underpowered to me. Most pontoons I see around Miami have 40-50 hp motors on them and get around 20 mph
Youy do need to get a tach installed??
 

junkman41

Petty Officer 1st Class
Joined
Oct 16, 2011
Messages
350
Most of those pontoon boats that I have seen have those hi thrust Micky Mouse ears type of props on them to power those rigs along at a steady speed, pontoons do not go fast, is your prop a three or four blade. It looks like you have a pretty large boat and Judging your boat by the picture a 20 hp seems underpowered to me. Most pontoons I see around Miami have 40-50 hp motors on them and get around 20 mph
Youy do need to get a tach installed??

the boat I am referring to is my 16.5' alumacraft fishing boat, not a pontoon
thank you
021.JPG
 
Last edited:

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Most of those pontoon boats that I have seen have those hi thrust Micky Mouse ears type of props on them to power those rigs along at a steady speed, pontoons do not go fast, is your prop a three or four blade. It looks like you have a pretty large boat and Judging your boat by the picture a 20 hp seems underpowered to me. Most pontoons I see around Miami have 40-50 hp motors on them and get around 20 mph
Youy do need to get a tach installed??
 

junkman41

Petty Officer 1st Class
Joined
Oct 16, 2011
Messages
350
I talked to a dealer and was told I wont get much more speed on the 20hp so I guess I will just keep what I have....Thanks for all the replies
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I don't know what the wot is I don't have a tach, the boat is loaded it has a floor a casting deck livewell, me at 300 lbs, it just seems to me that I should be able to get more speed out of this motor, I was thinking a high thrust prop, but not sure of the pitch
thank you
It's critical for the health of your motor to have a gps Most cells have an app.
A tach is even more important as it can tell you how well your boat performs and what it may need.
You must know that when setup it is able to operate within its wot rpm rating.Once set up you can operate at at ever rpm yopu want with the throttle.
Induction tachs like the Tiny Tach will get you your rpm.
With the info we need we can tell if you can improve things and tell the results when done.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I talked to a dealer and was told I wont get much more speed on the 20hp so I guess I will just keep what I have....Thanks for all the replies
We don't even know what speed your at that dealer said you can't improve on.
I can definitely tell you we can improve very likely improve your overall performance
Hole shot, ability to stay on plane at reduced throttle. May even improve handling around the dock.
I have to guess about the present prop but it is slightly on the high side of the chart very likely causing lugging
Which can cause premature repair problems.
Prop selection can result in a peppier boat that gets a tiny bit better mileage.
 
Last edited:

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
You want to better top end speed, but haven't said a word about hole shot, it's poor, so-so, can live with it ? Improving top end speed sacrifices best hole shot with an underpowered engine which assume is so for that size boat. You can always maximize a prop to some extend. But impossible without and induction tach installed to know max wot rpm achieved with that current prop while lightly loaded preferably on flat calm no wind water cond.

Happy Boating
 

junkman41

Petty Officer 1st Class
Joined
Oct 16, 2011
Messages
350
thanks guys, I will purchase a tach and install it then see where I'm at as far as RPM's. as for the out of the hole speed, I think it is pretty sluggish, I think I should have more speed all the way around. I will install a tach and get back to this post and let you know where the rpm is at wot.
thanks Jack
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Can't have both of both worlds, that's fast hole shot with better top end speed in just one prop. If you have in current use a 10 pitch with slugish hole shot and acceptable top end speed, going for say a 11 pitch will achieve awfull hole shot with slight better top end speed than before once on plane. If going for a niner pitch will achieve better hole shot than with a 10 or 11 pitch, but with slight less top end speed than with 10 or 11 pitch, that's if only playing with pitches. A tach will confirm RPM readings while playing with prop pitches and GPS for wot speeds.

Happy Boating
 
Last edited:

junkman41

Petty Officer 1st Class
Joined
Oct 16, 2011
Messages
350
I downloaded a tach app and a gps app, now I have to get down to the lake and see where I stand... I will post the results
thanks guys
 
Top