What's the ideal surfing RPM of a EX343?

[Z3CO23]

Johnnie when I owned my RZR I ran the 1617 here in Denver. I know it's a smaller boat but it was a tractor. When I owned it we ran it listed of course. We ran the equivalent weight of what a Taps 3 RZR probably goes weight wise for a good wave.

[HoopsMT]

I have been acing the exact same issue with my 2013 Z1. I'm topping out at 4100 rpm, 25 mph. That's with a 1235. I'm also not getting great ouch. I can no longer get on plan with any ballast. I'm talking 150lns of ballast I can't get to 10mph. I don't have any vibration issues, engine sounds great just now power or top end. Fingers it's either a cylinder not firing or fuel pump. Just changes all the plugs, no difference. We are looking at battery, thinking it is affecting the time of the fuel pump. No solution yet on my boat, but hope to have an update next weekend. If you figure yours out let me know. My top end was around 5100 rpm. Not sure where it went.


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[JohnnieMo]

Lower RPM, such as going with a larger prop, is not always the way to go. Need to be mindful of getting the rpm too low and the engine out of its ideal power band.

With my past hands on experience, tge trailer has been the driving force behind prop diameter on the Z1. If the trailer allows, I think a 14.5 is a good dia for a loaded Z1. Theres a couple good options in the 14.5" dia. This will drop the rpm a little compared to the 1433, but not too much.

I think I am going to stop worrying about the trailer. I don't load under power anymore anyways, so I think this is moot. If I need to, I can shim the bunks again. I have a couple inches clearance into my carport to work with I am not afraid of RPM either. The amount of gas burned is more a function of "work" than a function of RPM. Obviously RPM will increase usage, but I don't want to be too hard on a slow turning motor.

Inorder to accurately give you the best advice. Your Drive ratio etc needs to be listed. I am guessing its a 1.5-1. If thats the case, and your trailer allows, I would try and squeeze a 15 inch diameter prop underneath. Lets then set the pitch and cup where it needs to be to keep the motor happy. The benefit of the bigger Diameter (within reason of course) is that allows for a more efficient transfer of power to the water. There is a obviously a limit within each motor and drive ratio combo. I cant see a reason for going anything other less then a 15 inch diameter prop if you have the room and have the 1.5-1 ratio.

Food for thought...... For every 40 thousands you add in cup it is essentially like adding 1 inch of pitch. To a point, you can go this route and not really give up any on the bottom as the change in cup really isnt felt until into the power band and on plane.

Very good info. I appreciate you weighing in. I have always assumed that bigger props need bigger motors for the most part. However adding diameter and taking away pitch could likely solve my issue.

Listing only. TAPS2 single center tab.


The 1235 made a HUGE difference compared to the factory 537. We've kept the 537 as a backup but we've never installed it since the 1235 showed up.

I did the same thing, but with the 1433. The 537 is still my spare. If I go ahead with a more aggressive prop I think I'll have a 537 as a wall decoration.

Johnnie I have a 1235 you can try, you can grab it next week.

Awesome! Please bring to surf night. I'll try it later this week. Has it ever been repaired, or is it in new condition?

I have been acing the exact same issue with my 2013 Z1. I'm topping out at 4100 rpm, 25 mph. That's with a 1235. I'm also not getting great ouch. I can no longer get on plan with any ballast. I'm talking 150lns of ballast I can't get to 10mph. I don't have any vibration issues, engine sounds great just now power or top end. Fingers it's either a cylinder not firing or fuel pump. Just changes all the plugs, no difference. We are looking at battery, thinking it is affecting the time of the fuel pump. No solution yet on my boat, but hope to have an update next weekend. If you figure yours out let me know. My top end was around 5100 rpm. Not sure where it went.

This sounds like a different issue. I don't think I have a power problem. I think I have some sort of balance or alignment problem that is preventing the power from getting out. Afraid I'm not much of a boat mechanic, so I can't give you any insights. I do know my boat will rev up to 5200 RPM if I let it. (just not with all the ballast)

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In general, I pull a slalom skier about once per year, and might do a long cruise at ~25MPH once a summer too. I would give all that up for a tractor-like surf machine.

I went out surfing again yesterday and with two people in the boat was able to load the front full, left rear full (1300), and right rear to 75%. Had a monster wave with no vibration at 3200 RPM. The vibration tends to come in if the boat hits any form of chop or if you turn sharp. This coincides with the RPM increase. To me that smells a bit like cavitation - perhaps compounded by the mangled propeller.

[chpthril]

I think I am going to stop worrying about the trailer. I don't load under power anymore anyways, so I think this is moot.

Its not a clearance issue loading, but when the boat is nested and the trailer is pulled from the water and boat sits fully on the bunks. Thats when you run out of room.

[JohnnieMo]

Its not a clearance issue loading, but when the boat is nested and the trailer is pulled from the water and boat sits fully on the bunks. Thats when you run out of room.

I have about an inch clearance in that situation right now. In the past I've only ever hit the guard when the propeller is moving. Since shimming the first time the issue has resolved.

I'm not sure if all trailers are this way, but mine is highest right at the back. As the boat gets nested the measure actually increases. (i.e. the prop guard is not level with the ground) Since the trailer typically sits lower at the back (in the water) you don't hit.

[Germaine Marine]

Ideally you would increase the diameter as far as you could clearance wise and within reason motor wise. Then you would back down the pitch and cup accordingly. The more surface area the better transfer of power you will get.

For example... a 17x14 with .40 cup runs approximately 37mph, has excellent speed holding fully ballasted, great hole shot and runs at 3650 at 12.2 mph.

By increasing the diameter to an 18x14 .40 cup... There was a slight increase in bottom end, a reduction in RPM by merely 200 and an increase in top end by 2 mph.

[Germaine Marine]

I would go bigger then a 1235 if you can fit and I would dial back the cup and the pitch. 2315 if you can fit it would be my choice......

[Germaine Marine]

Call Todd at Acme.... and get an exact from him.

[chpthril]

I think a 15 is going to be a bit of a struggle for a 343 and a 1.46 gear.

[JohnnieMo]

Is anyone on the forum running an EX343 with a 15" prop?

[Germaine Marine]

Johnnie I just spoke to Acme... They have hours and hours of testing on the 343 with 15 inch props. No problem. That motor actually builds its torque a little lower in the Rpm range. If the 1235 isnt enough for you I would go to the 15 knowing full well that the 15 isnt too much prop for that tandem..

[Germaine Marine]

The 1235 is going to be a little lower Rpm wise then say the 2315 at surf speed.. The 2315 is going to have more bottom though, so if the 1235 cant seem to hack the weight and or give you what you want then the 2315 would be my next stop.

[Germaine Marine]

the 2773 might also be a good bet

[JohnnieMo]

Just for interests sake I attached the GoPro to the trailer to get an appreciation for how much the boat floats off the trailer on launch (and presumably on loading). This is that video.

https://www.youtube.com/watch?v=HWI_...ature=youtu.be

As you can see, the boat gets extremely high up. So long as I don't power load it, I think I'll be fine.

Speaking of power loading, the guy beside me in the video (MB Tomcat) got his trailer stuck in the launch. He went too deep and his boat fell off a 2 foot drop beyond the concrete. We had to lift his trailer out by hand. That's the effect of power loading!

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In other news I completely forgot to put on KillerBren's 1235 (which is happily sitting on my workbench) before my surf session tonight. Dammit! Will have to wait for the weekend. This lake is a bad test anyways because the weeds foul up even the best propeller frequently.

[IDBoating]

Speaking of power loading, the guy beside me in the video (MB Tomcat) got his trailer stuck in the launch. He went too deep and his boat fell off a 2 foot drop beyond the concrete. We had to lift his trailer out by hand. That's the effect of power loading!

Yep, power loading is right down there with power turning as a cardinal sin of boating, justifiably punished by fines in the thousands of dollars for a first offense. In fact power loading is the worse of the two, since it causes lasting damage that affects everyone while power turning's waves eventually die out.

Our ramp at our lake has the same problem of erosion at its deep end. The lake level got especially low two years ago and we actually couldn't use the ramp to pull our boat for the season. We had to use a shallow beach between two people's property; the slope was so shallow that I had to back the truck into the water to the bottom of the front doors, and even then we barely got the boat on the trailer. I have a full size loader/backhoe and would have loved to smooth out the huge hump of sand and gravel dug out by the power loaders, but the State can't have a private citizen fix such things for free! No, they have to hire it out... to a guy who shows up with the same class of loader/backhoe and does the exact same job at taxpayer expense.