Impulse help!

[sigma962]

New to the forum, first time posting.
Been involved w RC cars for long time and just bought an impluse 31...the calm lakes in my subdivision were too good to pass up.

Need some help with Impulse set up. I cant get the porpoise effect to go away. Ive changed battery location, trim tab settings, prop strut angle...combos of all three. I cant get it up on the pad and make it stay at full throttle. Bounces a lot at full throttle but at 3/4 speed it doesnt bounce but is not all the way on the pad.

The pond, man made, I run on is huge and glass. suggestions?

Running stock gear, 4s in series 5000mah 30c batteries.

Thanks.

[G-UNIT]

I woulds say put everything back the way it was, strut in a netural or level position and bend down your trim tabs a tad more, mine did that out of the box and thats all I did and it runs fine weather I run 4s 5s or 6s.

next just try and move the batterys fwd just a little at a time and test again.
are you running a stock prop or some thing else?
try an m445 it works very well on this boat, and check your temps.

[stadiumyamaha]

Lowering the tabs worked for me as well. It was very bouncy out of the box and now it rides perfect all the way to 55mph.
Watch out for stuffing though, especially in rough water.

[bluznbeers]

Take your average credit card debit card whatever and put it beneath the trim tams, then lower the trim tabs until the card is in line with the bottom of the hull, this sets the trim tabs at just about a perfect height. Good luck.

[Steve McGinley]

I know this is an older thread but I thought I would share what I've discovered. My Impulse was bouncing violently after I brushed a stray tree branch laying in the water. After the impact I inspected the boat and saw absolutely no damage other than the rudder break off screw was missing. I replaced the screw and tried a run, the boat was bouncing violently. The faster I went the more the boat would bounce. What I had discovered was that my turn fins were pushed back when I brushed that tree branch. I moved the turn fins closer to the front of the boat and problem was solved. I didn't think that the turn fins could cause such a violent bounce!

[stadiumyamaha]

It's my thought that you have turned your turn fins in to trim tabs by giving it a little rear drag. You may want to bring the fins back up and lower the tabs. Less drag and better speeds without making it work as hard. Jmo

[Steve McGinley]

I will try that, so you dont think the turn fins are the real cause of the bounce? I'll set the tabs back further and lower my tabs and see what happens. Thanks!!!

[stadiumyamaha]

Try that. IMO the fins shouldn't start dipping in the water until you start making a turn. Also make sure your rudder is close to vertical. If its tilted rearward it causes lift, if forward it will push the nose down.

[Steve McGinley]

I tried your tip and it worked great!!! I lowered the trim tabs so they were even with the bottom of the boat and set my turn fins back and no bounce! How far back do you set your turn fins? Are your fins about horizontal to the profile of the boat? You had mentioned that turn fins should only make water contact when turning pretty much so I would assume yours are just about horizontal?

[stadiumyamaha]

My fins are turned up all the way.
I wouldn't move the tabs down but slightly bend them down. You want the base of them a little higher than the bottom of the hull.

[Steve McGinley]

Thats what I did, I took a.credit card and layed the side of the card on the bottom of the hull, with the trim tabs set an eight of am inch from the bottom of.the hull I bent the tabs downward until they touched the card. I set the turn fins back but I think I will set them back even further now that you told me where yours are set. Thanks again! The boat has alot less drag now and should have even less when I set the turn fins all the way back. I shouldnt affect stability right?

[stadiumyamaha]

glad its working for you. If the fins are to far back the worst that will happen is it will spin out in the corners.