Propeller options

nestorpr · #1 10-19-2006, 11:55 AM

Hi Kahuna, my boat used a 19" pitch prop and I could reach about 4200-4300 rpm fully loaded, not the best but close enough. This gave me about 32 mph again fully loaded with the Bimini up so it's not a bad setup. Unfortunately the motor seized up this spring for unknown reasons. The mechanic told me these models tend to do that once in a while but I can't see why, especially when the oil and temperature were always OK.

By the way, are you in Hawaii? I'll be going to Oahu in Dec. to visit my son and grandkids, if by any chance you're close I'd like to see your rig if possible.

Kahuna · #2 10-19-2006, 09:43 PM

Hey Botapeje, You are turning a 19 x 13.75. Ok, sounds good. I think I'll go with that. Since mine is a little older motor (still with low hours) I think I'll stay with the aluminum wheel vice the stainless. Just to give it a little more slip and try not to load the motor. I usually don't run the boat much over 20knots now, the sea-state does not generally allow for it. Besides, if I needed to get there faster, I should have left 15 minutes earlier. LOL. I usually run mine pretty light (full fuel, but light people and gear). It sounds like that 19 should work ok, unless they make an 18.

I'm actually located in eastern CT (New London)and use the boat on Long Island sound, but it has MS registration #'s (house on the cape, this is the CT boat, cheaper to register there). I'm actually the third owener of this boat. The original owner was in SC, and the boat was indoor rack stored up until about 4 years ago, teh second owner ran it for about 20hrs, shrink wrapped and put away until late winter this year. I use all the original canvas and cushions. I ripped out all the wiring and original power (raw water cooled motor). The boat has never been technically "restored", but it is in better shape than anything we could find that was under 5 years old. Besides, now I have got something that is worth something.... Happy to show it to you. I'll see if I can get a couple of pictures. Thanks for the help everybody!!

nestorpr · #3 10-20-2006, 01:19 PM

I think you'll do OK since my motor's even older (1970!) and the aluminum prop works fine, especially here in South Florida where you have to run quite a bit in the shallow waters of Biscayne Bay until you can hit the pass and get out to deeper waters. Going through some shallow areas I've already banged up the prop in sand, small stones, coral and such. The aluminum absorbs the shock a lot better than SS and it's cheaper to repair or replace the prop than the lower unit! Good luck with yours!

Kahuna · #4 10-22-2006, 02:16 PM

Just got back from a ride, perfect day for it!!! 3850rpm, 30.2 knots on my Garmin plotter, full fuel, light load, trimmed out so it is just short of starting to porpious. Even at 3850, that motor doesn't sound like it should be spinning that fast. 2-stroke outboards sound better the faster you spin them. I have only run a Regulator with 225 4-strokes. This is my first experience with an I/O. I guess it is ok. At 3200, it is running 21-22knots. Plenty, still going to change the wheel.

Bigshrimpin · #5 10-23-2006, 11:29 PM

Drop down to a 19 pitch highfive and I'll bet you'll see close to 40mph @ 4500 on the top end. High five is a thin blade 19pitch prop that gives great sternlift and is super smooth. The hubs kits for these props are designed to break if you hit bottom and spares are about only $40.

http://www.mercurymarine.com/dealerlocator

and select "demo props" there are a list of dealers that will let you try props before you buy . . . You can always buy a aluminum 19P after trying some other props.

ThePHNX · #6 11-20-2006, 05:01 PM

Kahuna:
Thinking of moving up from 19" to 21" prop but your figures bother me. What is your drive ratio? If the 1.65 that translates to over 30% slip! Than again is your plotter reading from a speed transducer or the GPS. If GPS the speed through water is unknown and that's what the boat speed really is. Don't blow my head off for mentioning the obvious but are you reading MPH or Knots? (the plotters will read whatever you choose or has been set.)
If we go to a more reasonable 10% slip, than true hull speed - through the water - for a 21" wheel is 41.6 which allows for a 9 mph current, not unusual, moderate in fact in tidal channels but then do you have much tide or current issues in Hawaii? The Latitude suggests little tide but plenty opportunity for currents.
HBH

spareparts · #7 11-20-2006, 06:08 PM

140 mercruisers should have a 1.98-1 drive ratio, unless its be changed to high altitude gear set ( 2.20). the other ratios available are 1.84, 1.65, 1.50, 1.32. The later Gen II's had different ratios, but the are very close to these

ThePHNX · #8 11-21-2006, 11:31 AM

The 1.98 still gives a 21% slip, on the high side of reasonable.
Kahuna, next time you're out try a proper speed trial, run the reciprocal: first run at whatever bearing convenient, second at 180 degrees opposite, take the average of both runs.
Also, what does your wake look like?
Spares, is it common for the gear ratio to be changed by the user? How can the ratio be verified, short of counting teeth? How many reduction points are there on a sterndrive, more than one?
HBH