Prop Choice??

[Warwgn]

Found the OEM prop should be 13 3/4 x 21, right now I have a 14 1/2 x 19. I need to change the prop because it is making me run way too many RPM’s to get a good speed. Getting up on plane and cruising at about 20-25 MPH I am turning 3500 RPM and WOT is pulls 4200 and hits about 30 -35 depending on how I trim the drive. I have just the 140 HP 3.0 so not expecting 50MPH but just want to drop my RPM’s while cruising on plane.
I was thinking of a 14 ½ x 23 pitch, that should still give enough grunt to pull a tube for the kids and cruise easy at lower RPM from what I have read but I am not really sure what to get and have got good advice on here so far so thought I would ask. We have a shallow lake and run up the river a lot so will stay with just aluminum prop for cost and incase I hit something which happens a lot where I boat from what I have heard from a few local people.

 

[Lazy Daze]

You're going the wrong way. That 19" prop is really not even getting you into your spec'd WOT RPM range. Double check, but I think the MAX for your engine is about 4,600 - 4,700 (something like that, anyways). That means if you go higher in pitch, you'd be dropping WAY out of your recommended range. You'd end up lugging the engine and make it work too hard, which is bad. Based on the info you've provided, you should actually be putting a 17" prop on there. BUT, there may be other factors at play here - tired engine, needs a tune-up, dirty bottom, heavy load in the boat, water logged, etc. It would be good to address those things before you do anything with props, though. But regardless, putting a higher pitch on there - based on things as they are - would be the wrong move.

 

[Creekwood]

Try a 17" four blade aluminum. They are cheap and if I recall you generally should drop pitch when you move from 3 blade to four. Your hole shot will be better with the 4 blade, it will plane better at lower speeds, and it will run much smoother.

 

[Warwgn]

yes I think it is a heavy pig for the engine I have which is old and tired I am sure, it is getting around 2.2 MPG, so not performing well at all. I did not think of a 4 blade prop, and with it being heavy I suspect you may be correct in that suggestion, it should help get it moving. It's not getting any lighter for sure anytime soon and I run with all three kids and coolers full of drinks and snacks for a full day, and will be adding more ropes and tubes so a 4 blade would prolly be best I will look at those now. Thanks

 

[Warwgn]

ok I did swap to a 4 blade 14.5x17 and it feels the same as far as hole shot and how it planes, I can get more RPM but speed has dropped off about 4 MPH. So ready for round two on this and I need to understand what the diameter of the pro does? I picked up new trim ram bushings and chatted with the sales guy at the boat shop about a new prop and the last bit he said as I was leaving was I should go with a 14 and I would get more torque.

SO my question is I know want more speed and cruise RPM to be around 3000 to 3400, right now with the 14.517 4blade I am cruising at 22-23Mph at 3600 - 3800 RPM and wot 4400 at 30 to 31 mph.

 

[Warwgn]

Ok so some revising and questions, caught a log or stump or just the bottom, but broke my prop again so time for another one.

I have to change some statements from before, I had too much time between prop changes and did not realize what the difference was on the 4 blade. After I put the 14.5x19 3blade back on (buggered up the four blade at the ramp) I did notice it took longer to get up on plane, but rpm was about the same WOT maybe 100 diff. But Cruising RPM was much better, was back down to 3400 vs 3800 to be at 28MPH, so the 19 pitch was better for cruising and getting around but pulling the tube and getting up on plane was not as good. I want to start water skiing too, and this 3 blade I fear would not pull an adult up, so need to change it up. I want the best of both worlds of course so need to figure out what to do.

Sea Ray said OEM was a 13 3/4x 21 for my boat, so I want to go to a 21 for sure, however I will not do it in a 14.5 dia prop, I see them in Solas aluminum 14x21 3 blade which I am sure would work and can find them used on ebay in 13 3/4x 21 in 3 blade in a Michigan wheel? I am thinking a 4 blade sure was nice but that 14x21 might make the engine struggle just a little too much, and the closest thing I can find in a 4 blade is a 12.5x21.

Ok Follow me here, 13 3/4x 21 is OEM and normally when going from 3 to 4 your supposed to drop pitch to keep RPM’s, well I don’t want to drop pitch and loose cruise speed but if I drop 1 ¼ inch in diameter and add a blade do you think that will give me the same or better torque and keep the speed? I am thinking the smaller diameter and same pitch with an extra blade should all equal out to being almost like OEM but with a bit more push to get on plane and pull tubes and stuff?

Any thoughts?

 

[Lazy Daze]

I think there's a better way. You're never going to get "the best of both worlds" with one prop, especially with 30 year old 4 cylinder. If this were my boat, I would use the prop that I felt offered the nicest cruise speed, but still allowed the motor to reach comfortably into it's rated, MAX WOT RPM. THEN, for the hole shot and "torque", I would install (about an hour install) a set of Smart Tabs. That's pretty much as close to the best of both worlds as you're going to get. The other thing you could do is have one prop for "cruising days" and one for "watersports days". But, the first way would be my choice.

 

[Warwgn]

Genius, I did not know about smart tabs, they look like just the ticket. I think I can still try the 12.5x21 and hope that puts me in the cruise and RPM range I want, then if it does not pull hard enough I will add smart tabs, and after that I will try again with just prop choices to fine tune it all in. I do like the Idea of just swapping out props depending on use, or just swap them out on the water. Use the speed prop to get where I want then a quick change while the kids are swimming and off we go on the tube.