Should I mess with my prop pitch?

[MrWesson]

I have a 1971 19-6 with a 140 johnson that has a 15px13.5 prop.

Obviously the boat gets up and goes with neck snapping quickness but obviously runs out of breath on the top and cruises a little slower. I havent really tried to max it out due to a lack of calm water and being alone but with one other guy it would take a long time or may never hit 40mph(seen 37 I think).

Most of my running is down in slow speed/no wake zones and I find I have to run at about 2500-2900rpms to maintain a slow speed of about 6-8mph wasting alot of gas.

From an efficiency standpoint should I go with a bigger prop or will it not make a difference?

[fitz73222]

I have a 1971 19-6 with a 140 johnson that has a 15px13.5 prop.

Obviously the boat gets up and goes with neck snapping quickness but obviously runs out of breath on the top and cruises a little slower. I havent really tried to max it out due to a lack of calm water and being alone but with one other guy it would take a long time or may never hit 40mph(seen 37 I think).

Most of my running is down in slow speed/no wake zones and I find I have to run at about 2500-2900rpms to maintain a slow speed of about 6-8mph wasting alot of gas.

From an efficiency standpoint should I go with a bigger prop or will it not make a difference?

Hi Mr. Wesson,
The answer is yes. A 15Pitch on a 140 on a 19-1; (if your boat is a '71 it's a 19-1 and not a 19-6 which is a completely different hull dead rise) would be considered under propped in either case. The best prop to run for all occasions is a prop that delivers the maximum RPM's in the upper range of what the factory allows with your normal load. So for your 140, assuming an older OMC and healthy, would be 5500-6000 rpms at WOT. So with your normal load you would want to see 5750-5900 as a good range to deliver the best performance throughout the engine's range of throttle and torque. When propping this way, you get the best overall performance for just about everything you might do for the normal use of the boat. I would venture to say with a 15 pitch propeller you are going to be at or over 6000 rpms at full throttle with a light load. If you don't have a tachometer, install one and see what the engine is delivering with this propeller. Many factors will need to be considered before you find the right prop. The good news is that with a GPS and tachometer we should be able to find the right propeller that will work best. So what are your full throttle RPM's?

[MrWesson]

I have a 1971 19-6 with a 140 johnson that has a 15px13.5 prop.

Obviously the boat gets up and goes with neck snapping quickness but obviously runs out of breath on the top and cruises a little slower. I havent really tried to max it out due to a lack of calm water and being alone but with one other guy it would take a long time or may never hit 40mph(seen 37 I think).

Most of my running is down in slow speed/no wake zones and I find I have to run at about 2500-2900rpms to maintain a slow speed of about 6-8mph wasting alot of gas.

From an efficiency standpoint should I go with a bigger prop or will it not make a difference?

Hi Mr. Wesson,
The answer is yes. A 15Pitch on a 140 on a 19-1; (if your boat is a '71 it's a 19-1 and not a 19-6 which is a completely different hull dead rise) would be considered under propped in either case. The best prop to run for all occasions is a prop that delivers the maximum RPM's in the upper range of what the factory allows with your normal load. So for your 140, assuming an older OMC and healthy, would be 5500-6000 rpms at WOT. So with your normal load you would want to see 5750-5900 as a good range to deliver the best performance throughout the engine's range of throttle and torque. When propping this way, you get the best overall performance for just about everything you might do for the normal use of the boat. I would venture to say with a 15 pitch propeller you are going to be at or over 6000 rpms at full throttle with a light load. If you don't have a tachometer, install one and see what the engine is delivering with this propeller. Many factors will need to be considered before you find the right prop. The good news is that with a GPS and tachometer we should be able to find the right propeller that will work best. So what are your full throttle RPM's?

I do have a tach but in most situations I get to run full speed in I have to pay close attention to wakes from other boats(some up to 4ft sportfishers) so I cant stare at it. Next time I try to pay attention.

What do you mean it has the same deadrise of the 19-1? the hull layout at least the looks and interior look to be exactly the same as other 19-6's. I also should ask what the deadrise is of the 19-1.

[RickK]

Look at the bottom on this one - is this the way yours looks like? If so, it's a 19-1.
http://www.classicaquasport.com/phpbb3/viewtopic.php?f=1&t=8770&p=74541&hilit=191#p74541

[MarshMarlowe196]

The main difference between the 19-1 and 19-6 is the 19-1 has a "pad" that extends all the way to the transom. The 19-1 has a bit less deadrise than the 19-6, and the console on the 19-1 is further forward. There are a few other differences as well.

Stern of a 19-6:



Stern of a 19-1


Here's a picture of the pad on the 19-1, the 19-6 has no pad:

[MrWesson]

what would be the handling and main differences between the two?

[MrWesson]

been scouring the internet for answers and cant really find it being discussed but what are the handling characteristics of the 19-1.. I mean I have one and know how it handles but not sure what I could do better.

Mainly the wall of water coming over the front when the bow buries between wakes(spray rails seem to be in order).

I will have to look at the back of the boat but based on pictures of the front deck I have a 19-1.

[RickK]

I'm not sure there are much difference in the handling between the 2 models. I think you need to keep the bow up a bit crossing the waves or hit them at a different angle.  These boats (all of the models) are considered "wet" in the wrong seas anyway.

[MrWesson]

So in the spirit of this thread the 19-1 is probably a couple hundred pounds lighter than a 19-6 and should be propped with a higher pitch prop?

the 15p that is on there seems even more out of place right?

[Blue Agave]

Until you provide the RPMs you are currently getting at WOT that question is difficult to answer. Be careful not to over rev the motor.

[MrWesson]

Until you provide the RPMs you are currently getting at WOT that question is difficult to answer. Be careful not to over rev the motor.

Havent been able to reach WOT these days. Running in the atlantic only and no wake everywhere else here in lauderdale makes it tough.

I will say to get to 20-24mph I have to touch and exceed 4000rpms.