24' Monarch Fun Island Pontoon

jamie f

Recruit
Joined
Apr 26, 2015
Messages
5
Just got this boat this spring with no motor.Rated for a 90 hp motor.Purchased a 1984 90 hp mercury and installed it.Currently has a 13.25 X 17 prop.Took it out to test it today and it runs around 4400 rpm's at wide open throttle and doesnt want to plane properly,seems to be diving front end down more than it should and cant bring it up by raising trim.Jumping ahead of myself i ordered a new prop yesterday,a 13.25 X 15 prop.Joined this group today and after reading some prop threads it seems i may have to go lower on pitch than what i ordered.Was told motor should run around 5400 rpm's.Any one have any advice on prop pitch and rpm's?I would appreciate it.Thanks, Jamie
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
You want around 11 pitch. You engine you be running around 5500-5800 to be healthy.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I agree a 11" prop is a good starting point. Pontoon speeds are all over the place with no obvious reason.
Many times a 24 may be as fast as a 18 0r 20 with the same hp even though much heavier.
Pontoons don't really plane and don't get up on the water like a mono hull.
If yours seems to be diving perhaps the trim isn't working right.Or perhaps the transom is weak.
Note the attitude at rest usually about 1/2 submerged at the stern and obviously higher at the bow.
If there is water in the tubes it may list to one side or sit lower in the water.
 

jamie f

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Joined
Apr 26, 2015
Messages
5
Thanks for the info guys.I found a 11 pitch prop but it is 14" as opposed to 13.25.Is this going to affect performance very much?I have plenty of clearance to install 14" prop.On another note,trim is fully operational,transom is very solid,and no water in toons.I'm hoping it is all in prop selection.Any thoughts or suggestions are appreciated.Thanks,Jamie
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
14" diameter is normal for 11 and 13 pitch props.
 

jamie f

Recruit
Joined
Apr 26, 2015
Messages
5
Thanks guys.I'm a newbie at this prop stuff.The other boats i've owned have been all set up already by previous owner and performed good.First time setting up from scratch and its been an adventure to say the least.I appreciate all the help,Ive ordered 14 X 11 prop and i'll post back when i test it out.Thanks again!!!
 

jamie f

Recruit
Joined
Apr 26, 2015
Messages
5
Thank you very much SkiDad and Steelespike!!Installed 14 x 11 prop,took it out and tested it with my wife and our 4 kiddo's,ran at 5400 top rpm wide open throttle and 24 mph on gps.Very happy with this boat and really appreciate the help.Kids are looking forward to tubing tomorrow.Once again THANK YOU!!!!This is an awesome site with a great group of people and alot of information.Jamie
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
Nice speed! when I pull people on tubes I try not to let the rope get slack so that no one is jerked around. 20 mph is plenty fast for tubes.
 

jamie f

Recruit
Joined
Apr 26, 2015
Messages
5
Yes the tube manufacturer recomends 15 to 20 mph tops,also,older kids have some tubing experience.Cant wait for this rain to pass.Feel like a kid with a new toy.LOL
 
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