Motor height / transom questions

[Dino2000]

Hello all,

Recently I've been researching props, engine height, etc... to get better efficiency as I don't believe my 18 foot Pontoon (powered by a Suzuki 60hp 4-stroke) is properly equipped. WOT is about 4,000 rpms so I just ordered a 13 pitch prop to replace my 17 pitch prop. Now I'm trying to determine if I have the correct engine height. Below are pics of my current setup (ignore the absence of a prop as the new one is one the way).

Do any of you have experience with engine height? Can you provide me with some insight please? Thank you in advance for considering.

 

[crb478]

Re: Motor height / transom questions

I can not tell you if your motor is at the right height or but don't be afraid to experiment with motor height. I have had my current motor in all four different positions. I started at the bottom went to the top then lowered it one hole and thought I had it set, but it was just two of us on the boat. Loaded it up with people and I had to lower it one more hole where it currently is. You will then need to prop it to get the correct rpm's and then you may still need to raise or lower the motor again. Hopefully the rpm's will still be right or you may have to re-prop yet again until you get it dialed in as well as the boat motor combo is as good as it will get. Also one hole can make a bigger difference than you probably think it will.

 

[MaPaHa]

Re: Motor height / transom questions

Good advice ^^^. Comments like that can save a lot of time. Things change a bit with a two tube pontoon vs a regular boat or even a tri toon. The old standard is to set the cavitation plate right at the water line but you can't go by that only with a pontoon. I've got mine set an inch or so below but its a tri toon. Too shallow and it blows out too quickly when trimming and in turns, and too deep and it's a drag with extra water spray.

 

[bav/270w]

Re: Motor height / transom questions

Water line on the motor while boat is at a stand still position doesn't mean anything. It is when the boat is underway is underway and how the water comes out/ off the transom. Have you tried using your trim? Motor should be all the way down on take off to prevent bow rise and should be trimmed up while accelerating to achieve balance between top speed and rpm. As mention above, this all changes with the amount of load you're carrying at the time. You didn't say how many people where on board. if it was six to eight, that quite a load for and 18 footer and you won't get good performance.

 

[Dino2000]

Re: Motor height / transom questions

Ok... So I replaced the prop. (Results below). Now the question is do I raise the engine?

Boat: Sweetwater 1880 Pontoon Boat (dual logs)
Engine: Suzuki DF60 (2002 4 stroke)
Passengers: 1 (myself)

Old Prop: 13.25 x 17 (3 blade)
- WOT RPM's = Appx 4000
- WOT Speed = 18 mph (GPS)
- Torque out of the hole = Poor
- Cavitation = Poor in turns

New Prop: Solas 13.25 x 13 (4 blade)
- WOT RPM's = Appx 5200
- WOT Speed = 23 mph (with trim)
- Torque our of the hole = Very Good
- Cavitation = Very Good All Around

Now.. time to possibly make more adjustments. I'm now wondering what an 11 pitch prop will do? Maybe increase RPM's by another 200 or so?? Also... Feel like I need to test with weight as I was the only occupant. I'm also considering changing the depth of the motor. Like many pontoons, my stern is very low in the water and at WOT my transom creates a ton of drag (just can't get the stern up high enough). Wondering what to do at this point.... Wondering if I should raise the engine... See pic below.




Hope this info helps others... please feel free to post thoughts and/or ideas if you like. I'd appreciate all the info and experience I can get.

Thanks for reading!
- Steve

 

[bav/270w]

Re: Motor height / transom questions

Sounds like your getting close to me. I'm not familiar with your engine's WOT range. But if you have more room on the top end an 11 pitch may help. At this point I'd raise motor 1 hole at a time and see, easier and cheaper, well maybe not easier but definitely cheaper. by raising motor you would have less drag on lower unit. It's all trial and error from here. I used to have a 1990 20' bass buggy with a 60 hp evinrude 2 stroke and about the best I could muster out it was 22-23 mph.

 

[crb478]

Re: Motor height / transom questions

I would have a few people sit up front where they seem to gravitate to any way and test it again. weight up front will pull your prop up higher in the water anyway. If all is good try to raise it one hole and go out again. I have gone to the ramp with a floor jack and the proper sized wrenches and moved the motor to three different holes testing between adjustments, just pull the boat out move motor and back right back in. I really think that you are getting pretty close to your desired set up. From here it is all how do you boat, how many people are on board, and how much do you want to spend chasing 1 or 2 mph

 

[Jeep Man]

Re: Motor height / transom questions

Your very close to the max. WOT for your engine (4700-5300). The only possible improvement would be a 4 blade 11p prop which will give you a better hole shot and better reverse control but doubtful if your speed would increase. Typically when you go to a 4 blade you drop the pitch by 1 to keep the same RPM. Underskinning will give you a couple more MPH.

 

[Dino2000]

Re: Motor height / transom questions

Raised the motor and saw very little difference in performance but did see some cavitation.... Gonna have to lower it back to it's original location. Tests complete.... Gonna leave it as is. Hope this helps someone else.

 

[Bamaman1]

Re: Motor height / transom questions

You'd probably really need an 11 pitch prop if you ever intend to carry any people with you. Your posted speeds are about as high as you're going to get with a rather small 60 hp motor.

I seldom see 4 bladed props on any pontoons as 3 bladed props seem best. Most 4 blade props go on bass boats with a bunch of horsepower to push'em.

Since you're technically capable, see if you can find some aluminum sheeting to install on the underside of your boat. You'd be surprised how much smoother they run when the waves are not bouncing off your crossmembers. And much quieter. It's just well worth the investment.

I'm running a new Bennington 24' tritoon with a Yamaha F150 hp motor. I've seen 42 mph GPS @ 6100 rpms with a 15 pitch stainless prop. It's nice to get up there and run with the full hulled fiberglass I/O's cruising the lake.