14ft mt48 Suzuki 20 new, rpms 200 high and slow to get on plane help

[Dillong]

Just got a 1448 Jon with a 20 Suzuki, with just me in the boat it over revs about 200 over and with me and my buddy barley gets out of the water on to plane. Talk to a gut at boat shop told me to go to a four blade prop same pitch to help get the butt end out of the water faster, just got new prop tried it out ventilated at 7mph 1/4 power. What should I do?

 

[steelespike]

I suspect either your new prop is defective or not intended for your motor.
We need to go back to your original prop and start over. Need to know 2 stroke or 4 stroke?prop size wot rpm and gps speed.
Its unlikely that a motor over rev with one aboard and bog out with the addition of one person.

 

[Dillong]

4 stroke. 9.26x10 3 prop normal load runs 6800,24 mph on gps and rev limiter cuts out motor and takes about 7 sec to get on plane. Boat is a mod v Jon rated for up to 25hp have a 20 on it should not be under powered. Speed is not big on list just want it to handle better at half throttle.

 

[steelespike]

Upon further contemplation if the rev limiter is cutting in changing to a 4 blade same pitch may be ideal It should help the hole shot and drop the rpm a
little.It is interesting that a 10" prop isn't listed here at iboats. Replacement props start sat 9".A 10" is considered original equipment.
So you have a setup that over revs with one buit struggles with 2. Small 4 strokes do sometimes struggle with hole shot but it seems odd to have your struggle.Perhaps there is a battery and tank in the stern?Trimming down (prop closer to the boat) may help
Does the new prop fit the gear case as it should?If there is too much space it will be fouled with exhaust.

 

[Dillong]

No battery, and with OME prop it vary slow out off hole no matter the trim. New 4 blade 10 pitch ventilates with 1/4 power, I can't find any problems with the new prop. Would it be over pitched with 4 blade 10p. What would you recommend for a new prop to add hole shot and plane faster. I don't care about loss of speed.

 

[jestor68]

Please identify the 10 pitch 4 blade prop you purchased, since Susuki doesn't list any 4 blades for that motor and I too don't see a 10 pitch 4 blade in the prop section.

It won't be the first time a shop sold someone a prop incorrect for a motor.

There is no reason that a 4 blade should ventilate worse than a 3 blade, unless it's not the correct prop for that motor.

I see 11 pitch 4 blade props listed here, which should work to bring the rpm within limits.

6800 rpm is 500 rpm over the limit of 6300; not 200 over.

 

[steelespike]

Problem is your already over revving normal solution for slow hole shot is to decrease pitch or go to a 4 blade for stern lift.
Lower pitch will further aggravate over rev.
I wonder how the rev limiter is activated If its tied in with the tach and the tach is off rev limiter would be off as well.
Do you have your passenger in the front seat till you plane?
6800 rpm and 24 mph indicates 22% slip thats a lot. Typical slip across the board is low double digits. I usually use 13% if I am guessing to do a calculation.
Some jons have 4 or 5 keels at times with 2 in front of the prop.Perhaps the motor is a little high and venting from the water disturbed by the keels.
Usually the anti vent plate(just above the prop) should be even with or slightly below the bottom of the boat some will run with the the plate above the bottom. With 22% slip you have to wonder about motor height.

 

[Dillong]

I only have one boat shop within 150 miles of here they order this prop solas 4113-093-10A. The anti vent plate at neutral trim is about an inch below the bottom of the boat. Going to try a different tach tonight with me and one other guy 180 lbs in back 160 in front. The exhaust gases with the new prop from solas look like it might be the problem. I have never had this many problems with my other Jon boats.

 

[Dillong]

Could I be over torquing the prop nut?

 

[steelespike]

I wonder if the thrust washer from the old prop was still on and then you added a new washer?
Just tighten the nut enough to make the prop tight. No play between prop, washer and fasteners.

 

[Dillong]

So the problem with the new 4 blade is that it spins out, marked it and it spun out. What would cause that to happen to a new prop?

 

[jestor68]

If you go to the Solas web site, you will see that the prop sold to you is for a 9.9-15 hp motor.

He sold you the wrong prop.

Solas Amita 4 blade props for your 20 hp motor start with 4213- .

Never mind. I must have had too much to drink when I looked at that.

 

[steelespike]

So the problem with the new 4 blade is that it spins out, marked it and it spun out. What would cause that to happen to a new prop?

So your saying the line is now broken? If that's the case the prop is defective.Perhaps it" spun out" because it's intended for a 9.9 as Jestor suggested.

 

[Dillong]

No the motor is a 2014 df20 same size prop as the 9.9 15. http://www.solas.com/newweb/propeller/news/brand.asp?cat=A&FkindNo=F13&SkindNo=S04&PdKd=AL

 

[steelespike]

So it would appear the prop is defective.

 

[Sea Rider]

Are you sure engines runs at wot at 6800, it's hell of a lot more revs than most other engine brands. Is engine well height seatedd and trimmed on transom ?

Happy Boating

 

[dazk14]

So the problem with the new 4 blade is that it spins out, marked it and it spun out. What would cause that to happen to a new prop?

Simple defect in workmanship. Many prop shops will not warranty a re-hub, so there aren't huge margins of error for integrated hubs.

If indeed that Suzuki uses the same prop as a 9.9/15 there could be an inherit Solas design issue with the 20hp torque, but that is simply speculation.

 

[Dillong]

That is the max it will hit 2 sec befor the motor shuts off, rev light comes on at 6450. Using guy on lakes 12 pich 3 blade till I get new one, boat hits 29 mph gets a little scary for a 14ft.

 

[steelespike]

Your 12" prop is 2" higher pitch than a standard prop.
If we guess 10% slip 29 mph is at 6032 rpm.If we use 13%(more typical slip) rpm is 6101.Site says 5300 - 6300 is motors rpm range.
If your over revving then your saying your hitting rev limit at 6450.the That puts your slip at 17% A pontoon boat usually has slip above 20 %.
17% is unacceptable.
Your jon probably has 4 or 5 keels these could be disturbing the water ahead of the prop.Is there anything on the transom or the bottom
(a drain hole) that might disturb the water?

 

[Dillong]

Nope I'm happy with the 12 pitch, the 10" was the one over reving sorry for the mix up