Prop tuning and selection for 1648 sea ark

I have a 1648 sea ark flat bottom with a 85 Johnson 30hp. Right now I have a 10.1x 13p SS prop that turns 5950rpm @29mph with just me in the boat. I have a 24v system up front for my riptide 80 as well as a cooler to store gear. It jumps up on plane fine. I am trying to decide if I want to go with the Solas new Saturn SS 10x14 or 10x15 due to my motor over revving with my current setup. I am afraid the 15p may be a hair too much and it would put me below the 5200rpm mark if I have another soul onboard. Any suggestions or opinions on my setup?

Here's a pic of what I'm working with

https://i1342.photobucket.com/albums/o768/erictetterton/7EEEE6FD-A18D-4631-B8F8-5EBA20DE8BB7_zpsxcn4zwl3.jpg
https://i1342.photobucket.com/albums/o768/erictetterton/1347309B-F3FA-480B-8FF8-993D0F27E950_zps1azsurz2.jpg
https://i1342.photobucket.com/albums/o768/erictetterton/5135DF8E-3B54-4AC9-8856-BD22004443FE_zpsulbfcdnm.jpg

I took the boat out yesterday and got some more numbers. With my girlfriend onboard it did about 28.5mph at 6050rpm with the 10.1x13p SS prop. How it jumped up 100rpm with one more person onboard idk? I am thinking the 10x15p Solas New Saturn SS prop may be the one for my setup. I really need to get my WOT rpm down to about 5500 for the sake of making my motor last.

Well I ordered the 10x15p Solas new Saturn prop today. I will post numbers when it gets here. Stay tuned

I think it will be fine. Do you use this boat for anything besides fishing? I run a 9.9x12 on a 1542 with a 25hp but, I pull my kids on the kneeboard often and I just put my old 10p on before heading out. Works out great. Good luck.

I like your stereo setup by the way. Did you remove the foam from that seat or just dig out enough to get it all in there?

Thanks. Nope all I do is fish and flounder gig. I removed just enough foam for the stereo and speakers to fit. It sounds great

erictetterton said:

Thanks. Nope all I do is fish and flounder gig. I removed just enough foam for the stereo and speakers to fit. It sounds great

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Yep, I like that. I thought about mounting mine in a box I could take in and out of the boat, but I'll probably mount mine the same as yours.

Did you get the ss 15p yet?

waterman said:

Did you get the ss 15p yet?

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I Have a Alumacraft 1648-15, Evinrude Frankenstein 30 HP long shaft tiller, mini jack plate.
Now to tell about the outboard; the power head is a 2004 25 HP with 30 carb, the rest of it is 1990 long shaft, it has a 10x11 prop.
With two adults about 500Lbs., fishing gear, 140qt. cooler full of ice, 55Lbs. trolling motor, one battery, lowrance HDS8 fully laoded; I can hit 28Mph. on the GPS, but not at WOT do the motor hits the rev limiter bogs the motor do to the prop. From a dead stop hit it to hard it will take you out of your seat and put you on the motor "if you are lucky", it can be to hard to handle at time with that prop. I was thing of going with the same Solas new Saturn prop SS 10x15.
How did it work out for you?

The 15p was a terrible match for the setup. I couldn't get the boat on plane. I stuck with what I had and sent the 15p back. I'm not all that impressed with the design of their new Saturn series. They are made for mid range performance and the blades are more rounded and not for top end performance. Their old Saturn series was better IMO

Take your 13" prop in to a dealer and have them send it out and have cup added to the prop. That should bring the RPM down a couple hundred. Cheaper than buying a new propeller as well. Turn around time is usually less than a week.

Outboards always run better when you take out your girl...

From what I have found at the prop shops for my setup in Stainless Steel 10.125 X 12 "for heavy load" to 10.125 X 14 "for speed" and Aluminum 10.125 X 13 "for load and speed". Your setup with out the floor about 75Lbs. on mine and I do not have a floor, but I do have one more bench seat with storage. I think a SS 10.125 X 13 work the best the RPM will go down about 100 to 200 and little more speed.

I think what you found was that the old adage of "1 inch pitch=200 RPM" doesn't really apply to motors smaller than, say, 75 hp. I've personally done some prop swapping on my 25 and found that 1" of pitch is roughly equal to about 400-450 RPM on mine. If that is also the case with yours, a 14" should be real close. Going over a hundred or two is fine, gives you a little more reason to put your tackle in it and load it down with your catch. Oh, and take your girlfriend.

Weather and water conditions also play a role in propping. Cold air with high barometer WILL make it go faster, and a few more RPM. Mine was on the limiter this morning, never run into that before with the current prop-but-the air temp was 22° and barometer was 30.96"/Hg. With the dewpoint of 12° F, I came up with a density altitude of around -2000 feet, which basically means that the motor thinks that it's running 2000 feet below sea level. That's pretty good air, in my opinion.

It's also possible that the Solas that you tried was really closer to a 16" pitch. One thing about some of the props is that there isn't much consistency with castings. Turbo tests every prop, and it takes roughly 30 days to build a prop from scratch. Once it's built, it can be mass produced faster, but they're ALL tested and if they're "off" any, they're usually recycled (melted). Turbo is now owned and run by Yamaha; they can be had for almost any motor just go to your Yamaha dealer and look through the catalogs. I'm tickled pink with the one I bought, Turbo "hotshot" 11".

Turbo hotshot ive heard make a good prop for those motors. I believe stiletto props are made by the same company. Ive also heard not so great things about the solas Saturn prop.

Your rpm could have gone up because of the climate or because of the weight distribution. With both batteries in the bow you may be a little nose heavy running solo. A girl in the back with you may get the rpms up a bit. Normally 3-5 test runs will give you better results to compare to.

Also what angle of trim are you running? Tucked in, out or level to hull?

Another factor of rpm is the motor height.

Jon boats can be a tricky thing to get setup 'perfect'. If you are as picky as I am you'll be constantly messing with it.

To answer your question, I do what pappy suggested and get it cupped or just leave it and run just under wot. If you're looking for better rpm and maybe 1 mph the easiest thing would be get a prop one pitch higher. Same brand and style. If you want more speed that's in another section.

I just went through this with my boat. 2015 War Eagle 648, 1996 Evinrude 25 HP. Came with a 10 x 15 prop on it. With me alone it'd run about 26-27. Boat has a 100lb battery, front trolling motor, full floor and a 6 gal gas tank and some gear. Add another person to that and it's down to 21-22. I put a new 10 x 13 AL prop on it today and took it out, same setup but just me. Top speed is the same but is MUCH quicker and sounds like it revs slightly higher. I am positive the 10 x 15 was too much. Jumps onto plane and up to 20 MPH in a few seconds. I'm positive it'll be much better with two or more people now.

I ordered an Turning Point Propellers SS 10.25 X 14. With 2 people "about 400Lb.", 2 seats, Cooler, trolling motor, fishing gear, 6 gl. of gas and my 31m AGM battery the hit 35MPH on rough water. Not to bad for that outboard.

How is it you guys are running the same size prop - granted on more powerful engines, with more weight and out pacing my 1436 almost 2:1...

I've got a 20hp with a 10.125x13p that would hit 20.5mph (regardless of how many people were in the boat) but I was running between 5900 and 6100 RPM when I should red line at 6000. I had a cupped edge put on, now the RPM's are down to 5700~5800 but so is the speed, down to 18.5mph max...trimmed pretty well level to the bottom of the boat (as best I can manage with the pin-hole style adjustments). If my weight were an issue I'm thinking the motor shouldn't reach its peak RPMs even at WOT correct?

I'm tempted to pull the trolling motor and batteries off for a run and see how it does. If that doesn't change anything (removing ~200lbs) then I'm going to try trimming it up to the next peg and see if a bit more angle will get the bow pointed a smidge higher and plane further toward the back of the boat, maybe reduce some contact area with the water.

Otherwise I'd have to hunt down a 10.125x14p and see how that performs.

nevermind...probably a difference in the final drive ratio between the larger and smaller engines...not comparing apples to apples...