23 pitch prop?

[kdiddle]

Morning, all. Quick PO rant alert - apparently my PO replaced the prop on my Doral 200 / VP 5.0 before selling to me (I couldn't water test it / long story) and now that I've been able to drive it some, I've come to conclusion that the PO for my boat was completely clueless in all things marine (this was already well established / see long story).

I'm currently unable to completely open it up due to still breaking in my engine, but I've been noticing on take off that it is very sluggish even with only two people on board. Yesterday, I finally took her above cruise speed and it was running 48mph at 3800 rpm with more throttle left. That confirmed my suspicion that it had a top end prop installed, and checking it showed it is a 23 pitch prop.

Here's my question - do the pitches only go 17/19/21/23? If so, I'm assuming my move will be to a 21 and I have read on here that 4 blade props are pretty favored among you guys. Should I wait until I can confirm WOT rpm before deciding if the 21 is the right one?

 

[Sea Rider]

Need to confirm wot rpm achieved as loaded on flat water cond before playing with props. On standard props that only have + 2 pitches whether up or down can be re pitched at a prop shop in one sizee up or down to suit your boat needs. Is used when wanting to fine tune an engine and 2 standard sizes revs too much or too low.

Happy Boating

 

[kdiddle]

Sweet, thanks for confirming my suspicions Sea Rider. I'll wait until I can sustain a WOT to see where the rpms top out.

Thanks!

 

[alldodge]

The 5.0 is not much better then a V6 so far as torque. You need torque to get the boat up on plane. As SR mentioned we need WOT to determine the final outcome, but your not doing to bad right now. Don't know which ratio drive you have but if its a 1.5 then your slip is only 4.7%.

Don't know what year or if its a carb/EFI/MPI. Assuming an MPI with WOT of 5000 and same 4.7 slip this will say the boat will be doing around 60 + MPH. The ratio is probably off but you get the idea

 

[kdiddle]

Sorry, AllDodge - left out some important details. Yes, its MPI (2004 GXI-E) and it shows WOT of 4600-5000 on the decal. I'm unsure how to determine my ratio, but my drive is a DP-SM 1.95 (M22). Does that mean I have a 1.95 ratio? I've looked at some online prop calculators, but I don't even know where to begin coming up with half of the required values...

I'm glad to hear I'm not 'far off' but I couldn't imagine doing 60+ mph in this boat. I get what you mean about the torque of the 305 and would gladly sacrifice some top end speed for some low end jump (of which is has none currently).

 

[Scott Danforth]

a DP-SM has two props as that is a Duo-Prop drive. Please confirm that is what you have. your first post leads us to believe you have an SP drive

if that is the case, what are the prop part numbers (you have to pull the props to get the part numbers)

volvo sould only list a type D or Type F prop for the DP-SM


http://www.volvopenta.com/content/d...r-owners/parts/propellers/Propeller Guide.pdf

 

[kdiddle]

Well now I'm freaking out, since now it looks like the OP swapped the gear unit on it for some untold reason. See the attached label, it definitely shows DP-SM and I don't have any good shots of the stern drive except a terrible screenshot from when I cranked it the first time. Any other way to identify what unit I have???

 

[kdiddle]

BTW the label on the back says 'SX' if that factors into the identification.

 

[Scott Danforth]

Motor could have been swapped.

however the drive is a SP (Single Propeller)

SP props are rated by pitch.

 

[kdiddle]

Well, crap. Look what I found in my pile of papers, an unused label for an SX-M 1.60 (3868891). I wasn't able to find any paperwork on the drive being swapped, but I found an iboats.com receipt for a hub kit (3590504) and a 14-23 propeller (3593423), so it looks like I have to accept that the drive was swapped for some reason in the past...

This is why people don't like buying used boats, isn't it?

 

[kdiddle]

Scott - the engine is still a 5.0 (I actually just installed a new one), so I assume the SX-M somehow was compatible with this set up? Or they swapped the pivot housing and everything at some point. I'm going to go by the storage place and see if I can find some #'s on the drive somewhere...

 

[Scott Danforth]

pull the drive, get the serial number off the area where the bellows is. this will tell you what you have for a drive.

recommend you do a bellows job on it too.

 

[kdiddle]

Unfortunately I just put it back together after a new engine, u-joints, bellows, seals...the works. I never caught that it had a different drive in the process.

Is there a way to confirm the drive is the 1.60 SX-M without taking the drive off (again)? I'm assuming the answer is a big old no, but I had to ask...I assume I might be able to plug in my prop #'s with a 1.60 ratio and see if that comes out to the 48mph at 3,800 that I got the other day...

 

[Maclin]

I would believe the 1.6 paperwork...

 

[alldodge]

I would believe the 1.6 paperwork...

Only issue I have is the .05 slip, no way that's correct. I plugged it into bblades and it comes out to 7.21 which is good

 

[Maclin]

That .05 represents 5%, my arbitrary choice. Just pointing out that the numbers were in range, and with tolerances in MPH and RPM gauge readings....in line with what kdiddle might expect from their calcs.

 

[QBhoy]

5% is achievable for sure.
Anyway. 23” sounds too highly pitched for that set up...even with a 1.6 ratio.
I tried a 23” on my own boat with a 1.47 ratio. Has similar RPMs wot to yourself or a little more at 4200. Can’t remeber the speed.
Went to a 21” and it was much quicker and brought the RPMs up to just about in the range. Usually run a 19” thoigh for all round.
To answer your question about what pitch increments they come in...generally odd numbers with 2” increment, but I do know the Enertia seems to be an exception to the rule and comes in 1” increments.

 

[89retta]

That 23" prop looks in bad shape. Try a new prop and see what your numbers are.

 

[kdiddle]

Thanks for the feedback everyone. I'm going to try to run it tomorrow to see where my WOT rpm is, but after playing with an online prop calculator, I might be more prone to lean towards a 19 due to needing to occasionally pull skiers and more often than not, I'll be loaded with more folks than less. Since my max rpm shows 5,000 (and each prop increment down moves rpms up approx 400) I just need to ensure that I'm currently running no higher than approx 4,200 rpm at WOT with my 23 pitch prop. Right?

Who knew there was so much math in boating...

 

[kdiddle]

Morning, all. Quick follow up and question. I took it out yesterday and with only myself on board and water like glass, I was only able to get it to 4200 rpm at WOT. My engine labels says max rpm is 4600-5000. If my math is correct, my moving to a 21 should put my WOT at 4600, and going to a 19 should put me at 5000 WOT. I'm really more concerned about having some low end, and not sure that the 21 will make enough of a difference. However, I'm don't want to have to run at 3000 rpm just to be able to cruise on plane with the 19 (an exaggeration, but you get my point).

Any input here?