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is my boat set up right ????????

Posted: Mon Apr 30, 2018 8:48 pm
by achiggy
Im some what new to airboats. sold my first dd boat just got my second boat. its a 14' predator with a sbc 350 with a 2.1 rotator gear boat with 2 blade sensenich prop. I'm turning 4200 rpm on the motor. it just barley will run on flat dry ground. my question is what should i do to check that every thing is set up wight for the may put and thrust that the boat is capable of doing? everyone as told me that a 350 with a gear box will run dry.

Re: is my boat set up right ????????

Posted: Mon Apr 30, 2018 9:07 pm
by BenBad
Is 4200 RPM wide open throttle? Which 2 blade sensenich propeller do you have? A car engine should turn 5000 RPM or more. If 4200 RPM is wide open your blades need to be pitched differently. Let us know where you are located and maybe someone close to you can help get the blades pitched properly.

Re: is my boat set up right ????????

Posted: Tue May 01, 2018 8:52 am
by SWAMPHUNTER45
How long is the prop ?

Re: is my boat set up right ????????

Posted: Tue May 01, 2018 7:26 pm
by achiggy
BenBad wrote:Is 4200 RPM wide open throttle? Which 2 blade sensenich propeller do you have? A car engine should turn 5000 RPM or more. If 4200 RPM is wide open your blades need to be pitched differently. Let us know where you are located and maybe someone close to you can help get the blades pitched properly.



there 76'' when the boat is siting on the ground and i give it full throttle it really only at like 400 rpm the boat won't even dry load on the trailer . I'm in Plant City Florida and ride on lake kissimmee but would be willing to meet up with some someplace if they would help me with the boat.

Re: is my boat set up right ????????

Posted: Tue May 01, 2018 7:27 pm
by achiggy
SWAMPHUNTER45 wrote:How long is the prop ?
76''

Re: is my boat set up right ????????

Posted: Tue May 01, 2018 9:30 pm
by Basin_Runner355
You need to be in the 5,000 to 5,200 rpms a 350 don’t make peak power till about 5400 and i was told sechnich blades take more motor to spin than others

Re: is my boat set up right ????????

Posted: Wed May 02, 2018 7:27 am
by BenBad
I guess I should have asked if it is a wood prop. If it is a wood prop you have what you have and it would be the wrong prop for that motor. I do not know how to read the pitch on a wood prop but they are not adjustable and you would need a different prop.

Re: is my boat set up right ????????

Posted: Wed May 02, 2018 8:12 pm
by achiggy
BenBad wrote:I guess I should have asked if it is a wood prop. If it is a wood prop you have what you have and it would be the wrong prop for that motor. I do not know how to read the pitch on a wood prop but they are not adjustable and you would need a different prop.


no they are carbon fiber props not wood. so should i try and take pitch out of them?

Re: is my boat set up right ????????

Posted: Wed May 02, 2018 9:20 pm
by Basin_Runner355
Yea somewhere between. 5,000 and 5,200

Re: is my boat set up right ????????

Posted: Wed May 02, 2018 9:25 pm
by achiggy
does taking pitch out and rising rpm actually create more thrust? i know I'm probably asking dumb questions that should already be know. I'm just need to the airboat world ad just trying to figure out what needs to be done to get my boat running at its max potential .

Re: is my boat set up right ????????

Posted: Wed May 02, 2018 10:46 pm
by hdsadey
Not that I know a lot but isn't that ideal rpm range for a 2 blade prop 2600 to 2900 for max thrust? Sounds like too much pitch draggin down the engine. Neither peak torque or peak thrust is being obtained.

Re: is my boat set up right ????????

Posted: Wed May 02, 2018 11:29 pm
by BenBad
Achiggy, You stated that you have a 2:1 drive. If your engine is turning 5000 RPM then your prop will be spinning 2500 RPM. You need to take pitch out of the blade to allow the engine to turn more RPMs to get the prop speed up. I used to run a stock 400 SBC with a 2:1 belt drive on a 14 foot BullFrog Marine hull. I could run dry with 3 to 4 full size men on my boat. 250 to 300 pounds each person. I could turn 5500 RPM and had a 76 inch 2 blade R. The combo worked very well.

Re: is my boat set up right ????????

Posted: Thu May 03, 2018 3:45 am
by Basin_Runner355
On my boat i pitch it to 4900 for hunting season to run the water better with big loads on long runs to our camp and in the summer i pitch them to 5200 and that makes a big difference on my dry running.

Re: is my boat set up right ????????

Posted: Thu May 03, 2018 10:00 am
by nebraskaairboater
Depends on what prop you have... the S series works best for me at around 1850-2150 prop rpm, the R's seem to work better around 2100-2300 prop rpm. Multiply the prop rpm by the reduction ratio to find ideal engine rpm. You are 2-1 so double the prop rpm to find target engine rpm. They are all different depending on your combination and setup as well as how YOU like to run. So get to an ideal rpm and go up or down from there to find what works best for YOU. Keep in mine the safe rpm limit for the prop you have so you don't over rev the prop.

Re: is my boat set up right ????????

Posted: Tue May 08, 2018 6:58 pm
by achiggy
Took it out this weekend and yes for sure its only turning 4300 rpm on the motor the props are set on the #2 setting. That is if they are set right the #2 marks on the blades are lined up with the center of the hub where the front and back 1/2 come together.

Re: is my boat set up right ????????

Posted: Wed May 09, 2018 9:36 am
by nebraskaairboater
Best advice is to find out which prop you have and find the safe rpm limit. Then play with it until you find what you like. Don't exceed the limit rpm from the prop manufacturer though. Take pitch out will increase rpm and adding pitch drops rpm. I would assume you have an R blade which has a safe limit of 2800 rpm. Check level of the engine to the stringers. Level the stringers on the trailer then check level of the engine. I always start dead level to the stringers and fine tune from there. Up on the prop side of the engine raises the nose of the boat. Do you have poly on the bottom or at least slick bottom? Fiberglass wants to stick to the ground without some kind of slick on the bottom. I would slowly take pitch out and see how that affects the way it runs on the ground. Go to Sensenich website and download the installation instructions http://www.sensenich.com/shop/airboat/r-series-blade/ so you use the correct procedure to set the pitch. You are probably way down on torque with your engine only spinning 4300 rpm. It probably doesn't make decent torque until higher in the rpm.

Re: is my boat set up right ????????

Posted: Wed May 09, 2018 9:20 pm
by BenBad
What nebraskaairboater said............

Re: is my boat set up right ????????

Posted: Wed May 09, 2018 9:46 pm
by achiggy
nebraskaairboater wrote:Best advice is to find out which prop you have and find the safe rpm limit. Then play with it until you find what you like. Don't exceed the limit rpm from the prop manufacturer though. Take pitch out will increase rpm and adding pitch drops rpm. I would assume you have an R blade which has a safe limit of 2800 rpm. Check level of the engine to the stringers. Level the stringers on the trailer then check level of the engine. I always start dead level to the stringers and fine tune from there. Up on the prop side of the engine raises the nose of the boat. Do you have poly on the bottom or at least slick bottom? Fiberglass wants to stick to the ground without some kind of slick on the bottom. I would slowly take pitch out and see how that affects the way it runs on the ground. Go to Sensenich website and download the installation instructions http://www.sensenich.com/shop/airboat/r-series-blade/ so you use the correct procedure to set the pitch. You are probably way down on torque with your engine only spinning 4300 rpm. It probably doesn't make decent torque until higher in the rpm.

the boat has slick bottom on it but its old ill be putting new gator glide on it this weekend. thanks for the pointers

Re: is my boat set up right ????????

Posted: Thu May 10, 2018 10:59 pm
by Slidin Gator
350's like to spin and #1 pitch should get you over 5,000 RPM. You will gain thrust at minimum pitch because you are putting more power to the air, particularly at slow speed on ground. Gator Glide is a great move to attack the real problem, friction. When the paint is new it will be night and day, just plan to repaint every year, it won't hold up running ground, it will be obvious when it wears through. Don't apply that stuff when the humidity is high, it makes a difference in durability.