Evinrude 15 prop selection, have all the tech info. Just need advise!

Swilkins614

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It very well may be weedless, not too sure. The new prop is 9.25x9, old was 9.5x10. I may be going back to 9.5x10 though.
 

Swilkins614

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Btw, Iboats was extremely fast with shipping! Very happy with their phone service as well. Very friendly women working in for them! Will certainly be ordering from them again.
 

Sea Rider

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Although ideal is to work inside safe facory wot parameters stated for any given engine, it's much better working at min middle rpm, personally like going to its max but that's solo driving and lightly loaded boat and that's untill you beging adding more weight or passengers in which max rpm will drop accordingly. Hope new prop it's a better performer than old one.

Forgot to mention earlier that if you need boat to work trimmed all the way down, you probably will have prop aereation when engine is trimmed as stated on prevous post due to engine sitting still high on transom.. Once correct engine/transom height is achieved prop will work fine.

Happy Boating
 
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Swilkins614

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You prove a good point. I think ii need to just buck up and go do some real world testing. Next week I will have time to get out and run a little. I will also be bringing my used stock prop to try at the new engine height. I plan on bringing my Garmin so that I can video the run and also verify speed at the same time!
 

Sea Rider

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The lower tail posted pic is not visible, don't know what happened, assume you have cheked it. This vid shows what you should aim for. Water flow skimming slight under small upper plate when on perfect plane. Check how smooth and flat is its middle wake.

http://www.youtube.com/watch?v=oBeZjaA76VM&feature=youtu.be


This boater had horrible performance with his set up, follow the suggested posted trail sequence and is now working flawlessly. Does not need to be a Tohatsu, just need to be well transom height matched.

Happy Boating
 

Swilkins614

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Well I took a trip to Lake Michigan this afternoon after work for a little small mouth fishing. Got a little testing done with the motor as well. With the 9.25x9 prop I now run 20-21 mph with no significant increase in acceleration. WOT RPMs rose to 6600 from 6330. The boat seemed to handle better with the 10" prop. Plus I do kinda like the extra 2-3 mph. However, when at wot it does seem to have a more broad power band due to being higher rpms.

Also, I took some pics while on plane. Currently the motor is 1.5" above the transom and the anti vent plate is about even with the bottom of the hull. At this point I feel I need to move my battery up front. It seems the boat may be rear heavy when planing causing the motor to go even deeper into the water than usual. Heres a pic. From what it appears, the motor needs to go even higher.
 

Sea Rider

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Move weight that is sitting aft, gas tank and other stuff up front to better balance deck weight. If you don't have water splashes out or over transom that engine is seated correctly. Looks like water flow at speeed is well dialed passing slight under small upper water deflector plate. If you move engine up and depending by how much, prop will work fine on straight flat water courses but will aereate on fast hole shots, choppy sea cond andt at close tight turns at speed.

Test moving more weight up front and take another pic to see if water flow passing at lower tail has lowered a bit. BTW, how are you adjusting engine height on transom, with wooden shims, spacers, engine mount ?

Stay with prop that gives better hole shot no matter if losing some knots at wot. Can't have best of both worlds, that's good hole shot with good top end speed at same time, as one opposes the other. Anwayy, you won't be running wot 100% of the time. Good for faster hole shot and then backing up for less fuel consumption while mainatining combo on plane.

Happy Boating
 

Swilkins614

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I will be trying to move the battery and tank up front this weekend. Hopefully that will help with the squat at WOT.

Currently I am using .5" plastic shims. They are up so high I used two pieces of aluminum to sandwich them in place so the motor cannot fall off.

As far as I am concerned the 10" prop outperformed the 9". Same acceleration, higher top end. It appears many 15 evinrude motors are 5500-6500 rpm. I may go ahead and use that as my target. With the 10" pitch running at 6330, that's right where I need to be.
 

Sea Rider

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If it's too compicated just move fuel tank and extra weight except battery up front. My ex15 HP 96 Evi was wot rated at 5000-6000 rpm. Had exactly same prop type, it's not a weeder, it's a general purpose current prop.

Happy Boating
 

Swilkins614

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Well I went back to Lake Michigan today for some small mouth fishing. Interesting thing, I installed the 9.5x10 back on and now my rpms are only 6000. I did hit a log the last time I was at the river but I didn't thing it had that much of an effect on my prop. It is slightly bent plus the wear mark from the bearing carrier bolt backing out into it. Top speed was 21 mph this time.

Also raised the motor another .5", lots of spray coming from plate above anti vent plate. No increase in speed or rpms. The anti vent plate was riding right on top of water. Whole shot was terrible though. Dropped motor back down and whole shot got better but too end and rpms stayed 21 Mph and 6000 rpm

When I got home I started moving everything from the rear. Couldn't move the tank due to size. I have front decks and it wouldn't fit under them. Did however move the battery. It weighs 50 lbs so that should help a little. Next need to wire the battery back to my junction box in the rear. Hopefully I will have this done this weekend and I can take her out for a spin!

Smallies are on fire on Lake Michigan right now btw. Lots of piggies.
 

Sea Rider

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Sit engine were you had it on previous post, that's the ideal engine/transom height. You only need to play with prop pitches and move bat up front, leave fuel tank where it is. OTOH, you are expecting too much performance out of that 15 HP engine, you're already at near peak. The previos prop had much better hole shot with bit less speed, right ? If that's the only extra available use it,

Happy Boating
 

Swilkins614

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I believe you are right. I am asking too much from only a 15. I found a nice console steer evinrude 35 hp with all controls and Jon boat console. It's a screaming deal providing the motor has good compression. A 35 should make my little boat fly.
 

Swilkins614

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Well I decided not to go with the 35 Evinrude and instead bought an 88 Johnson 25. Also moved the battery up front. Wow what a difference. With the battery up front and larger 25 hanging off the rear the boat sits nearly level and flys! I couldn't too it out fully today but at one point I hit 28 on GPS. Thanks a lot for your help guys.
 
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