Mariner 150 Magnum EFI 13.75 X 19

[roughshot]

I upgraded my power this year on my 22' starcraft CC to a 150 Magnum EFI Mariner. The current prop is a 13.75 x 19 and appears to have been reworked/cupped. The Gear ratio is 1.87
Here is some basic info with GPS & RPM
RPM GPS Speed
4K 28-30 mph
4.5K 32-34 mph
5K 38 - 40 mph
5.5K 42 mph

WOT operating rage is 5250 - 5750 rpm

Don't really need more speed but may be nice.
Seems like this motor would push this rig a bit faster as the motor does not seem to be over worked when in the WOT range.

I'd like to go stainless if possible, maybe 4 blade?, any help on a new prop selection would be great.

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

Can I provide any more info that would get me a helpful response and pointed in the right direction?

Thanks,

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

Got some new data last night. My original post had a flaw. The original prop was not a 19p but a 21p.
I stopped to my local mechanic the other day an he loaned me a 23p to try out well last night this is what I found on the 23p.
Much smoother planeing acceleration than the 21p. I also brought my max WOT down to 5400 with the 23p from the 6K I was gettting with the 21p. My top end speed decreased how ever from 42 mph (GPS) with the 21p down to 38.5 mph (GPS) with the 23p. I would have assumed that I would have picked up a couple miles per hour. Motor turned the 23p without issue and no lagging. I know have another loaner prop that is 25p just to see how it compairs with the 23p and 21p.
The decreased speed with the 23p from the 21p kind of miffs me but maybe because the 23p was a "reworked" prop with thinner blades than the 21p and may have been flexing a bit.
Anythoughts?

 

[steelespike]

Re: Mariner 150 Magnum EFI 13.75 X 19

Assuming the specs are correct those props aren't doing you any favors.The 21 appears to have 28% slip
the 23 is at 38% about 6 to 12% is more normal.

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

So am I going in the wrong direction going up in pitch?
How can I correct this? I will try and get a picture of my mounted motor and where it sits on the hull for better reference as well. I was a little concerned with the higth of the motor when I mounted it this spring.
Here is a pic of the motor.

 

[steelespike]

Re: Mariner 150 Magnum EFI 13.75 X 19

From my research similar boats with 150s with similar ratios are running 16" and 17" props
Even on smaller aluminum boats.
I think your high slip is the prop design/alterations not the pitch.Normally the high pitch would lower rpm
which could raise slip. The props for what ever reason are just not good.Maybe thats why they are loaners.

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

I wouldn't doubt the loaner situation. Its just something to try for testing.
With the 21p I currently have, I didn't like the high RPM that it would reach at WOT.
If I went down to a 19, should I expect that the motor would rev even higher but not nessecarily give me any more speed but maybe less.
I will have to start trying lower pitches then.
Anythoughts on the "expensive" pitch shift props?

 

[Philster]

Re: Mariner 150 Magnum EFI 13.75 X 19

I'd go for a modern 19P prop. There are many flavors.

Couple of points here: Every time you mention a different prop, you must note the material, the pitch, the blade count and the make/type.

Also, you're all over the place. You need a clear goal that jives with reality. You want to go as fast as possible while being lower in the RPM range. This is somewhat conflicting. Rule of thumb: To go as fast as possible, generally you want to turn a 3-blade, modern design, stainless steel prop right to the MAX RPM range (to do this, you get a prop that can get you very close, but the theoretical prop that nails it would be customized).

Newer SS props have cupping for lift and raking for performance/snap. Oh, all these new fancy-shmancy prop have various am'ts w/ tweaks here and there, but slap a 19P on her, with a modern design, and hopefully she spins with the engine right up to max RPM or close. Well, that's for max speed.

Now, if you'd rather cut back on RPM, then you drop to an 18p, 4-blader and lose a couple-three MPH and enjoy lower RPMs and just better all around low and midrange, and some extra bite/handling thrown in.

EDIT: Wait, in the OP you show 5.5K @ 42 MPH, then you say later in another post she turned 6k???

Well, scew it, because the prop was worked. Now my baseline is the boat's performance with the 23P prop you borrowed. If we use that data, then you can just stick with a modern 23P if your goal is lower RPM, but I think it's too low. Throw some people and gear along with some fuel and your RPM are too low. Sorry. In that case, get a 21P to maintain reasonably low RPM w/out going too low.

If it were me, go back and read my initial recommendation. I'd want it running up near max RPM under a test load, because people, gear and fuel are gonna stick it into the Mid of the Max RPM range.

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

I'd go for a modern 19P prop. There are many flavors.

Couple of points here: Every time you mention a different prop, you must note the material, the pitch, the blade count and the make/type.

Also, you're all over the place. You need a clear goal that jives with reality. You want to go as fast as possible while being lower in the RPM range. This is somewhat conflicting. Rule of thumb: To go as fast as possible, generally you want to turn a 3-blade, modern design, stainless steel prop right to the MAX RPM range (to do this, you get a prop that can get you very close, but the theoretical prop that nails it would be customized).

Newer SS props have cupping for lift and raking for performance/snap. Oh, all these new fancy-shmancy prop have various am'ts w/ tweaks here and there, but slap a 19P on her, with a modern design, and hopefully she spins with the engine right up to max RPM or close. Well, that's for max speed.

Now, if you'd rather cut back on RPM, then you drop to an 18p, 4-blader and lose a couple-three MPH and enjoy lower RPMs and just better all around low and midrange, and some extra bite/handling thrown in.

EDIT: Wait, in the OP you show 5.5K @ 42 MPH, then you say later in another post she turned 6k???

Well, scew it, because the prop was worked. Now my baseline is the boat's performance with the 23P prop you borrowed. If we use that data, then you can just stick with a modern 23P if your goal is lower RPM, but I think it's too low. Throw some people and gear along with some fuel and your RPM are too low. Sorry. In that case, get a 21P to maintain reasonably low RPM w/out going too low.

If it were me, go back and read my initial recommendation. I'd want it running up near max RPM under a test load, because people, gear and fuel are gonna stick it into the Mid of the Max RPM range.

Thanks Philster. I completely understand what you are saying. With respect to the prop running 5.5K at 42 mph that is where I stopped with an increasein MPH and throttling up to 6K gained no mph. Prop Slip?
I liked the way the 21p prop work. FYI, all props are AL 3 blade, should have mentioned that and the boat is a 22' Al Starcraft hull, Deep V but relatively flat bottom that v's a little bit at the stern.
My goals are optimal speed just because I like to go fast but mostly I just want to find a prop that is optimal for the motor performance and longevity.

 

[Philster]

Re: Mariner 150 Magnum EFI 13.75 X 19

Would appear to be prop slip.

Optimal speed: You're doing it again! What is optimal to you? Optimal to one guy might be a few MPH short of top speed because he chose a 4-blade that is offering other advantages in low and mid-range performance! Optimal speed to me is every blessed RPM the engine has to offer!

Still, even the engine makers recommend propping up near the top of the RPM band. This way, when loaded up heavy or on a stifling hot, muggy day, the RPM will still fall into the max RPM range. This is kindest to your engine. What isn't kind to your engine is propping to the low to mid range of the MAX RPM range, then being all loaded up one day and at WOT not quite getting into the lowest end of the MAX RPM range. If a load condition like that exists, and all you did was prop to the lower end of the MAX RPM range with a light load, chances are you are lugging the engine the whole time you are out with a big load and/or hot, humid weather.

5700 or 5900 RPM at WOT is practically negligible in the big picture, but propping to the bottom of the max RPM range so that there are times under heavy load (or hot, humid weather) that you lose RPM or power... you have a lugging condition. Lugging = internal engine stress. Valves and bearing and such... they no like this. It's not optimal for them.

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

Would appear to be prop slip.

Optimal speed: You're doing it again! What is optimal to you? Optimal to one guy might be a few MPH short of top speed because he chose a 4-blade that is offering other advantages in low and mid-range performance! Optimal speed to me is every blessed RPM the engine has to offer!

Still, even the engine makers recommend propping up near the top of the RPM band. This way, when loaded up heavy or on a stifling hot, muggy day, the RPM will still fall into the max RPM range. This is kindest to your engine. What isn't kind to your engine is propping to the low to mid range of the MAX RPM range, then being all loaded up one day and at WOT not quite getting into the lowest end of the MAX RPM range. If a load condition like that exists, and all you did was prop to the lower end of the MAX RPM range with a light load, chances are you are lugging the engine the whole time you are out with a big load and/or hot, humid weather.

5700 or 5900 RPM at WOT is practically negligible in the big picture, but propping to the bottom of the max RPM range so that there are times under heavy load (or hot, humid weather) that you lose RPM or power... you have a lugging condition. Lugging = internal engine stress. Valves and bearing and such... they no like this. It's not optimal for them.

Thanks.
I'll start working down in pitch from 21 to find that top WOT RPM range of 5750. I can get that with the 21p I have but may like a 19 better.

 

[roughshot]

Re: Mariner 150 Magnum EFI 13.75 X 19

Ok.
After a couple weeks of testing I have found the following info.
I tested a 17p AL prop and got WOT of 5200 with a max speed of 32.5 mph
I tested a 19p SS prop and releaved my cavitation issue along with improved holeshot, WOT was 5700 - 5800 rpm with a max speed of 38.5 - 40 mph.
All props were 3 blade and now I'm happy with my 19p SS results.
I may look to a 4 blade when the money is available.