03 31’ jupiter twin 300’s prop size
07-01-2019, 06:31 PM
#1
03 31’ jupiter twin 300’s prop size
Hey guys. My 31 jupiter has twin 300’s with 16x23 wheels on it right now which i know is too big. The motors are also on the lowest mark on the armstrong bracket.
With about 175 gallons and only myself and one passenger I'm hitting 5250 rpms at 42 knots and approx. 60% trim at WOT.
The boat will usually have a 4 man crew with gear, ice, and 250-300 gallons of fuel for the long haul trips. I do not want to over stress the motors and it is definitely sluggish out of the hole.
So, should i go for 21.5’s or try even smaller?
thanks in advance, CJ
With about 175 gallons and only myself and one passenger I'm hitting 5250 rpms at 42 knots and approx. 60% trim at WOT.
The boat will usually have a 4 man crew with gear, ice, and 250-300 gallons of fuel for the long haul trips. I do not want to over stress the motors and it is definitely sluggish out of the hole.
So, should i go for 21.5’s or try even smaller?
thanks in advance, CJ
07-02-2019, 04:21 AM
#2
Senior Member
THT sponsor
Those props are way to big, I would drop down to 20's, this will get you closer to the 6000 rpm range where you want to be. You should be able to come up a hole or two as well with motor height from the sounds of. When up and running is the cavitation plate buried under water? Can you see it at all?
07-02-2019, 05:00 AM
#3
Thanks for the quick response. I figured they are too big. I haven’t had the chance to see the cavitation plate yet. My guess is that they can also come up a hole. I don’t want to worry about getting blow out in rough seas though. Do you think the 21.5 is still too big?
07-25-2019, 08:36 AM
#5
Thx for the info. My cruise right now loaded with 4 men at 4100rpm is 32-33 kts. Im pleased with those numbers for now. I wonder what rpms I would be at with 20’s to achieve the same cruise speed.
07-25-2019, 11:58 AM
#6
Admirals Club 
Originally Posted by schred86
Thx for the info. My cruise right now loaded with 4 men at 4100rpm is 32-33 kts. Im pleased with those numbers for now. I wonder what rpms I would be at with 20’s to achieve the same cruise speed.
07-26-2019, 06:25 AM
#9
Admirals Club
Originally Posted by Mozza
What's the gear ratio of the Suzi's? My cruise is 29knots at 4000, WOT is 50kn at 5900
04-07-2021, 07:28 AM
#13
Admirals Club
I have a 2007 31 with twin 300 Suzuki's and I'm running the 3x16x21.5 props. The motors are new (only 15 hours so far), but with a full tank of fuel, I hit 58 mph with a decent wind in my face. I'm guessing it would be a 60 mph boat light not going into the current (we have strong currents in SC - 6 to 8 foot tides), so it makes a difference. With a fishing load, we were running 40 to 42 at 4400 rpm getting 1.5 to 1.6.
