Long shaft vs 20 inch shaft motor on Pontoon?

I have a 22 foot tri-toon with a 150 Johnson motor and the center toon supports the motor that's built for a 20 inch motor. It will run ok but if you trim it out too far the motor will ventilate. I'm replacing my lower unit and have the chance of going to a 25 inch long shaft using the Bay kit. Once I put the top shaft on the lower unit it has to be completely disassembled if I want to change it later so I?ve got a one time chance to convert it now. The cost doesn?t bother me if it would improve the operation. I would most likely set the motor a couple of inches higher and three inches lower or something like that. Would this help having the motor lower to help on trimming out the motor? I know it would help the splash that the motor gets now but I don?t want to lose any speed. Is it a good change to make or leave it alone and go back with the 20 inch standard length? What do most pontoon boats have; a 25 inch or 20 inch shaft length?

Re: Long shaft vs 20 inch shaft motor on Pontoon?

Another thought I have is to use the 25 inch setup and run a jack plate to adjust the height. There's a lot of water spray out of the back so this might be a way to get the motor up a bit. Dont think I want to run it the full depth and most likely would run it several inches high and it would still be deeper than it is now. I just can't get it any lower the way it is.

Any input on the number of 20 inch vs 25 inch motors on pontoon boats?

Re: Long shaft vs 20 inch shaft motor on Pontoon?

most the pontoons I have seen use a 20 inch shaft. If you need to go slightly deeper why not pick up an adjustable jack plate and lower the motor you have? Or even better move some weight to the rear batteries gas tanks ect. It doesn't sound like you need to go much lower anyway. Also what type of prop are you running? A four bladed prop might be the only change you really need.

Re: Long shaft vs 20 inch shaft motor on Pontoon?

I like the idea myself. Others may chime in and disagree with me,but here's where I'm coming from. I'm building my first toon,which is a straked triple. Not a lot of experience to offer there,but I do have a lot of experience setting up mono hulls. I done a lot of research and watched videos of pontoons on plane. Plus I slept in a Holliday Inn Express.

My transom tube is patterned off of the typical factory center tube. When I hung my 20" Merc on it the 1st thing I noticed was it looked like it was mounted 2" too high,and it was bottomed out on the transom. The 2nd thing noticed was the transom angle wasn't enough to utilize much of the motor's trim. It'll blow out way before it's trimmed out. There's no way the bow will lift enough to keep the prop hooked up. I already planned on using a manual jackplate,but quickly decided on a hydr. unit because I believe I'll actually have to lower it once on plane to be able to apply much trim. So, I mounted the motor on the jackplate in a neutral position to start with,so I can raise or lower it.

This is the opposite of how you adjust on a fast v-hull. These long front heavy toons run much flatter,and will require much more leverage to raise the bow with thrust. My bet is once it's on plane I'll be able to drop it to give it more leverage for a better angle of attack to climb higher. Only need to keep it high enough to keep the cav plate out of the water. Question is where you cross the line of drag vs. HP when trying to create more lift. Things get really deep at this point,as there is almost infinite variables. The point of "is it worth it" has probably already been crossed. Kinda like trying to jerk the front wheels off the ground in a Grand Torino. Sure it can be done,but....

Something else that helps with thrust/bowlift on heavy dirty water hulls is a lot of rake angle on the prop. Looks to me like my straked center tube will trap a lot of air,which will mix (dirty water) and exit at the prop. The higher rake angle will draw water into the prop from further away,rather than directly in front. It also creates a tighter thrust cone which blasts further back into cleaner water for more "push". Not a lot of choices in high rake props in our pitch range. The best I've seen is the mercury Enertia,which is what I choose. I also bought some transom wedges (yet to be installed) to tuck the motor further under,and give it a more usable trim range.

I've also seen a lot of spray hitting the outboards like you mentioned. If you do indeed end up dropping for better trim the 25" shaft would definitely help. Was planning on making deflectors for mine once I see exactly what I need. Sorry for the long read,that's how my brain works. Again,this is just my theory. We'll know some results when I splash it soon and begin playing with the setup of this "Grand Torino".

Re: Long shaft vs 20 inch shaft motor on Pontoon?

Crb478,
Thanks for the reply. That’s good to know what the norm is because I thought there were more 25 inch motors out there for pontoons. When I had a Pontoon Water Glide under the boat I tried a jack plate (and a motor extension) to lower the motor and I never got the geometry worked out right. It seems the jack plates are more for raising the motor than lowering and the motor had a limited amount that you could tilt it for transport. If there was anyone but me operating the boat I worried about tilting too much and damaging the motor and/or cables. It also sat lower in the water than I liked and flooded out more than once where I had to pull the plugs and pump water out of the motor because of water spray picked up by the motor frame from the bottom and the steering cable from the top. I even built a splash shield to divert water from the bottom of the motor pod so it wouldn’t hit the frame and splash up. I never figured out how to configure a jack plate or motor extension to lower the motor successfully.
I’m running a Power Tech stainless 4 blade prop, 13 inch pitch series RXB4 with ventilation holes in it on an Evinrude 140. It’s advertised for acceleration, holeshot and all around handling. It has a moderate rake and cup. Since I added the third toon and brought the motor back flat against the transom that fixed most of the water spray but I still get some off the steering cable.

BrianMc,
I like you’re style. Go big or go home.
My old 140 motor definitely blows out before it gets trimmed out. I’m hoping with the newer 150 motor and set up I can find an adjustment that will fix that. Since I first posted I’ve ordered the 25 inch extension kit along with the lower unit. I dug out the jack plate that I tried before and maybe now since I’m lifting the motor instead of trying to drop it I’ll have success. I do think I’m getting “dirty water” into the prop at high speeds but I can’t prove it. I will have to change props because mine won’t fit the new motor and the new one will be a larger diameter. I’m going try a few from a source I have and then get the folks at Power Tech to help select the right one after I have some data. I’ll mention the high rake idea and I’m going to look up the Enertia prop and see how it’s built.

My 140 is rated at the crankshaft and the 95 model 150 is rated at the prop so hopefully I’ll gain 20 hp or so. It’s also 18 years newer. Right now the boat has a holeshot you wouldn’t believe and I’ve been ask to back off of it while pulling up an adult skier. I just run out of speed. Hopefully I’ll get enough horsepower to get the boat to the next level and take advantage of the lift that’s already under the boat. I hit 31- 32 mph at 5,500 rpm the other day after I took my hard top off. I was running 28-29 with it on.

Good luck on your boat and keep us posted on the progress. The tritons are a different animal and I’m still trying to figure them out. I’ve read where adjusting the length of the lifting strakes can make a difference and I’m wondering if shorting the ones on the center toons would make a difference in the water quality and balance.

I would like to know what the 22 foot triton, lifting strake boats are running with 150 hp motors that are set up right. I was told the other day by a guy that he was running about 40 mph with a 115 hp twin toon lifting strake boat but I’m skeptical. I’ve read other posts that upper 20’s is all. What’s realistic?

Re: Long shaft vs 20 inch shaft motor on Pontoon?

I would be skeptical about the 40 mph boat with a 115 unless its only about 16 foot long. I have a 24 foot crestliner pontoon with out lifting strakes, but with an under rated Yamaha 115 and it will only hit 30 mph with just cleaned toons on glass like water. speed drops fast with dirty tubes or rough water.

Re: Long shaft vs 20 inch shaft motor on Pontoon?

crb478 said:

I would be skeptical about the 40 mph boat with a 115 unless its only about 16 foot long. I have a 24 foot crestliner pontoon with out lifting strakes, but with an under rated Yamaha 115 and it will only hit 30 mph with just cleaned toons on glass like water. speed drops fast with dirty tubes or rough water.

Click to expand...

+1 ^^^

Re: Long shaft vs 20 inch shaft motor on Pontoon?

I've been on a new 22' toon doing 36 with twin toons and a 115 in fairly rough water.....seen the gps readings of 42 (better prop, slightly different setup) and the new prop I have heard has it pushing mid 40's. I'm gonna go test drive one again as soon as my wife and I get into our house and start looking for a new boat again.

Re: Long shaft vs 20 inch shaft motor on Pontoon?

I use to test props for Power Tech back when I was running center consoles. They have some good props,still have several setting in boxes. They had a 15 1/4" VMX patterned off of the Yammi T1 that would snap your neck if pitched right. It had the fastest 0-60 times on my 4000 lb 21' center console of any prop I tested. Just 13 seconds. But fell short of the T1 by a few mph on the top end. The blades were too thick and heavy on the big end. Their 15 1/4" OFX4 was probably the best flats prop out there,popping mine up on plane in a lil more than a boat's length. Would carry a butt load of weight,and a respectable top end. Tell Jack over there to splash the Enertia for us tooners,or make that VMX down to 13" pitch.

Out of all the different boats we tested props on we never found one where a 4 blade was faster. We could always top them with a big 3. If your faster with a 4 your not hooking up. Your either too bow heavy,motors too high,or the water is aerated. And since they're stern lifters the only way to reduce the wet surface area is by lifting the whole hull up. The rev4 had the best bow lift for a 4 blade,and the fastest too. It has a high rake blade. Faster isn't necessarily better though,as some choose 4 blades for their best all around.

The tilt problem with a JP is why I had to go hydraulic. My hydr. steering wouldn't let me tilt up if dropped the plate. I always got in the practice of raising the plate while pulling up to the dock. Is a problem if you let others drive your toys. Someone needs to make a momentary kill switch that'll kill power to the hydr. JP when cables,hoses,or motor bump the switch. Should come standard on hydr. JP's.

You mentioned length of strakes. If mine runs too flat I planned on shortening the outer strakes at the rear. You may be on to something cleaning up the water by shortening the centers. My center strake profile will trap air no doubt. It's a matter of how dirty it'll be by the time it slides back 26'. If the enertia doesn't hook the 1st thing I'll do is add a lil more tip cup. I built my toon to take a beating. Too heavy to be a runner. But, I always want to get the most out of a setup. Just tell the wife it's a guy thing.