should i reprop?

[coolbri70]

1968 Larson 18', 1979 evinrude 85 hp

trimmed out to the 3rd (middle) hole at wot 4200 rpm, 30 mph. if i trim it out to the 4th hole, its harder to get on a plane without losing traction, but once on plane i get to 4800 rpm, i have not checked the speed yet on that setting. these test were at minimum load just me and 9 gallons of fuel, my prop is 13 X 19, any advice appreciated

 

[steelespike]

Re: should i reprop?

delete

 

[steelespike]

Re: should i reprop?

As near as I can tell the motor is rated at a max of 5500.The range is 4500 to 5500.
Is the anti vent plate (just above the prop) about even with the bottom of the boat?
Your slip is pretty high at about 20% would be a little high at only 4200.
Is the prop in excellent shape? Bottom clean and smooth.
Is the foam under the floor dry?
You could go to a 17" Solas al prop,would probably give you about 5200 trimmed up.
And improve hole shot.If it gave about 10% slip you could get about 37mph.

 

[coolbri70]

Re: should i reprop?

i put new foam in, the bottom is rough with half chipped bottom paint i'm wanting to sand off, or if i wait long enough it will jus wear off:facepalm:

 

[steelespike]

Re: should i reprop?

The rough bottom will slow you a little.
How about those other things I wondered about?

 

[coolbri70]

Re: should i reprop?

View attachment 183737 the paint is wearing off but the edges are like new

 

[coolbri70]

Re: should i reprop?

i think maybe the lapline "million bubble ride" sends air bubbles in my prop thats why after raising it i ended up lowering it back down because it would ventilate when i trim it out, now that it is all the way down i can trim it out to the 4th hole, then i can not give it wot when taking off or it will ventilate and loose thrust, if i ease my way to wot then it will bite and goes 4800-5000 rpm. i have just not checked my speed at this setting yet. does it sound like its lugging at all? i dont really want to go faster, it gets too bumpy, just dont want to strain the motor. seems to have a good holeshot, better hold on anyway

 

[jestor68]

Re: should i reprop?

What Steelespike said. You need a 17 pitch.

 

[coolbri70]

Re: should i reprop?

there are several choices i see, whats best? i freqent shallow water so i heard i should avoid ss to protect the lower end. the solus has 2 in my size. which is best? do i go by price?

 

[coolbri70]

Re: should i reprop?

i see the rubex has some kind of different hub, watching promo videos but they dont tell much, mostly about qc in manufacturing

 

[jestor68]

Re: should i reprop?

Either one will work as they are identical except that the Amita has a pressed in hub, while the Rubex has their replaceable hub.

If you order the Amita, you need to order their thrust washer as well. In that case the Rubex is actually a few dollars less because that price includes the hub set and all the hardware needed to install.

If you get the Rubex, make sure that you torque the nut down to 50-60 lb ft to completely compress the rubber hub nice and tight. That will pretty much eliminate any vibration. You'll be surprised at how smooth these props run, as well as how well they perform.

 

[steelespike]

Re: should i reprop?

If there is one with a larger diameter pick that one, otherwise your preference. It appears the Rubex is a better price with the kit included.

 

[coolbri70]

after a year of more testing with the 19 the higher rpms were due to slipping when I was trimmed out too far, if I trim in and add the admiral to the boat, im only getting 3800-3900 rpms at 28-29 mph. so after breaking a piston and overhauling the engine, I convinced the admiral that it was due to lugging the engine and she finally let me buy a new prop. I know it was suggested that I go with the 17, but being an askhole, :indecisiveness: that I am, and figuring 400 rpm for every 2 inches, I'm thinking a 15 would get me to 4600-4700 and the motor being rated from 4500-5500 thought it be better, especially when I take a couple friends along. my new Amita 3, 15 pitch came today from iboats, it is mounted and imo looks spiffy:madgrin: hope it works out, I have to work Saturday, maybe sunday I can get to the river. when I do I will post results, thanks everyone:yo:

 

[coolbri70]

tried the new prop today, it worked great, I could only get 4400 rpms, 28 mph, but I did have guests, normally just me and the admiral, today my brother, his wife and my 2 nieces came along that's an extra 500 pounds, so to get a real comparison I will need to test again but I think it will get me in the recommended range:noidea:

 

[coolbri70]

going to the river today, just the admiral and I, will get to see how the new prop compares

 

[coolbri70]

got 4500 rpms, 31 mph today