Only getting 4700 RPM max

M Butler

Member
Messages
10
Reaction score
5
I have a new 20’ pontoon with a 90hp Yamaha. Prop is stainless with 13” diameter and 14pitch. At WOT I get 4700 rpm and 15 mph? Any suggestions?
 

Michiman

Well-Known Member
Messages
2,281
Reaction score
1,875
Location
Okemos, MI
SS on a 90 HP? That might be a problem right there. What is the suggested WOT RPM range for your engine? I know there are a number of folks on this site that have similar set-ups so hopefully they'll chime in.
 

Allan56

Active Member
Messages
41
Reaction score
40
I have a new 20’ pontoon with a 90hp Yamaha. Prop is stainless with 13” diameter and 14pitch. At WOT I get 4700 rpm and 15 mph? Any suggestions?
No suggestions but can give info to compare with - I have a 2017 20' / 25" toons lifting strakes /13 pitch/ 4 prop/ 90 HP mercury - top out at 5100 RPM and 30 mph 1 person perfect conditions
 

cwag911

Moderator
Messages
5,995
Reaction score
2,114
Location
Denver, NC on beautiful Lake Norman
Your prop is too big. Tell your dealer to get it right. That's what you paid for.
 

Mike31406

Well-Known Member
Messages
851
Reaction score
709
Location
Lake Greenwood, South Carolina
Congratulations on your new pontoon and welcome to the forum. Post pictures when you can.
 

BulldogsCadillac

Just some guy
Messages
4,079
Reaction score
1,582
Location
Dauphin, Manitoba
No suggestions but can give info to compare with - I have a 2017 20' / 25" toons lifting strakes /13 pitch/ 4 prop/ 90 HP mercury - top out at 5100 RPM and 30 mph 1 person perfect conditions
Really?? Wow, that is one of the fastest 90hp's I've seen on here, I think my old one was only around 24-25
 

M Butler

Member
Messages
10
Reaction score
5
SS on a 90 HP? That might be a problem right there. What is the suggested WOT RPM range for your engine? I know there are a number of folks on this site that have similar set-ups so hopefully they'll chime in.
6000 rpm is the max suggested
 

Allan56

Active Member
Messages
41
Reaction score
40
Really?? Wow, that is one of the fastest 90hp's I've seen on here, I think my old one was only around 24-25
Yes sir - start of the season with clean tubes ( stays in water at marina) I will hit little over 30 alone w calm waters- right now 27 or so - 25 w wife and Dog along - we cruise at 14.5 / 3500 rpm mostly - it’s a 90 Hp command thrust
 

the-little-B

Well-Known Member
Messages
209
Reaction score
191
I went through the pains of finding a prop to work on mine this summer too. I think I can help you out here. Mine is also a 20' , 90hp Yamaha , and 25" tubes.

Your rpm and speed sounds like a lot of prop slip to me. One prop I tried behaved like yours and it was because of it being the wrong style of prop. It was a pointy bladed prop , if you will , vs a more paddle shaped rounded blade needed on a pontoon.

Here is a short summary of props I tried...

Boat came with a 13.5x15 solas. Too much prop. Top was 4900-5000 rpm.

Tried a Yamaha "K" series 13 5/8x13. This was the pointy bladed prop and constantly cavitated and had no "traction" no matter what I did. Speed was in the low 20's.

Next was a Yamaha 13.5x14 Talon prop. Top was 4800-4900 but performed well. This is an aggressive prop and has cupped blades i believe and is too much for the 90. Had it repitched to a 12 pitch and now it's running 5500 +or- a few and does 26.5 mph.

Then I tried a solas 13.8x13 and am running 27-28mph depending on conditions and right at 6000 rpm.

I also raised my motor up one hole and can trim up to 3/4 on the trim guage with the 2 good props before it blows out and don't have any cavitation on hard turns either.

So there are a few numbers that I think will get you headed In the right direction.
 

the-little-B

Well-Known Member
Messages
209
Reaction score
191
Screenshot_20180810-081637~2.png d91b5c5f0e17a5265fda71008b2fc0a1.gif Amita3.png

Looking at the Power Tech props and most I saw looked like this style in the 2nd pic. The blades look pretty thin. The Yamaha K prop in the 1st pic is what gave me troubles and is what I was told by a prop shop a "shark fin" shaped blade and slipped like a son of a gun. It behaved like driving on ice and I had to feather the throttle to get the boat going without blowing out the prop. They are also pretty thin blades.

The last prop is the Solas Amita 3 that I am having good results with. The blades are much wider and more paddle shaped. The prop guy called em "Mickey mouse ears". A lot more surface area than the other two prop styles. The Yamaha Talon prop is similar but more agressive like I said earlier.

I don't get your low rpm's but I've found there are so many variables that 2 different brands of the same diameter and pitch will behave completely different. My boat is a 20ssx with couches in the front and fishing seats in the rear. I don't know but would guess it's one of the heavier models with that floor plan. If yours is similar I'd expect you'd have good results trying one of the props that is working for me.
 

M Butler

Member
Messages
10
Reaction score
5
It sounds like we have the exact same boat. I’m hopeful that this will solve some of the issues that I am having. I’ve also been told that a bad injector will make you loose the top end without running bad otherwise.
 

the-little-B

Well-Known Member
Messages
209
Reaction score
191
Sounds like your dealer is reading from the same page mine was when I told em I had the wrong prop. Wonder if it's the same dealer! Excuses were it's a defective prop , the motor is only running on 3 cylinders , etc. Bull crap! Lol! I had to do my own trial and error to find the right prop but have a buddy with a Yamaha too so borrowing props helped a lot! You'd think with as many boats these dealers sell that they'd have a clue what prop is needed. Get on em and demand they get you a prop that works!
 

Oldchuck

Well-Known Member
Messages
128
Reaction score
84
Location
Central Florida
Been researching the Yamaha performance reports and found a test with a Bennington 22 SSX with a 90 Yamaha.
They run a Talon SS SDS 13 1/8x14 #6N7-45970-00-00. They run 6,000 RPM at 30 MPH but this boat seems heavier than yours but you should be getting close to 6,000 with 30 mph running light..
 

Oldchuck

Well-Known Member
Messages
128
Reaction score
84
Location
Central Florida
On my above post, the 22 SSX with the 90 was a twin tube Elliptical which is faster but also heavier but given that Allan56 can achieve that speed then I think you should as well or be very close. He will have more torque with the 90 mercury and command thrust but the 22 SSX I quoted was with a 90 Yamaha on a heavier boat so maybe a wash. Either way, you should be seeing more speed with higher RPM with a different prop...
 

Mark Neumann

New Member
Messages
2
Reaction score
1
No suggestions but can give info to compare with - I have a 2017 20' / 25" toons lifting strakes /13 pitch/ 4 prop/ 90 HP mercury - top out at 5100 RPM and 30 mph 1 person perfect conditions
I have the same year and size boat with a 90 Yamaha. Tops out at 28 mph, 4800rpm.
 

the-little-B

Well-Known Member
Messages
209
Reaction score
191
I have the same year and size boat with a 90 Yamaha. Tops out at 28 mph, 4800rpm.


At only 4800 , you don't have the right prop either...

Some added info for you M. Butler...I was out today and running the 13.75"x13 Solas prop and with just me on the boat , all the gear and junk I got stashed on it , and a full tank of gas , and when I got away from the tubers n jetskis into calm water I was running 28-28.5 mph at maybe a needle width past 6000 rpm on my tach. I don't think a guy could do much better than that for our set up. I need to try that 13.5x12 Yamaha Talon prop again but it was too darn hot out there this afternoon!
 
Top