sbmarine

[a53hoop]

just got to try out my ml gsx338 hydro instantly nose dives.cog is half way on turn fin. strut centre is 1/8 below bottom of sponson with a very slight down trim.prop is cnc round ear style is qute extreme dive .any help?? tks Al

[Bande1]

move CG to 1" behind turn fin.

[Peter A]

just got to try out my ml gsx338 hydro instantly nose dives.cog is half way on turn fin. strut centre is 1/8 below bottom of sponson with a very slight down trim.prop is cnc round ear style is qute extreme dive .any help?? tks Al

From what you are saying the strut is too low and should be set flat. COG should be close but the way your strut is set is driving the boat under water. Start with the boat sitting on a flat surface and set the strut height so the bottom of the tub is level and the strut is flat. Test and adjust from there.

[DeltaAPmech]

Sorry I missed this post. I have the same boat and have been adjusting it a little at a time. Today it hit 73mph my new personal best.

As it sits today, it balances 1.5 inches behind the sponsion ride surface trailing edge. The strut is set at 0 degrees to the bottom of the center section with the centerline of the strut .074" above the bottom of the sponsion ride surface.

Mine also will dive underwater with the first application of power but I have found when it bobs back up hit the power fairly hard just when it pops up to its highest point and it jumps up on plane and takes off. Sometimes a little left rudder seems to help at that first hit when it pops back up too.

Pete

[a53hoop]

sorry ive been late to thank you guys as have been just able to try again. did all agustments sugested. raised strut to bottom of sponson and now 0 degrees.i have been moving my cog back from rear of sponson is now 3 inches.have tried all kinds of different throttle aplications but still instantly dives. i am very confused with this. tks AL

[Bande1]

sorry ive been late to thank you guys as have been just able to try again. did all agustments sugested. raised strut to bottom of sponson and now 0 degrees.i have been moving my cog back from rear of sponson is now 3 inches.have tried all kinds of different throttle aplications but still instantly dives. i am very confused with this. tks AL

I said 1" behind the turn fin not 3" behind the sponson.

[a53hoop]

was just playing with cog to seeif would make a diff. was originaly at 1 in.

[Bande1]

was just playing with cog to seeif would make a diff. was originaly at 1 in.

listen carefully... 1 inch behind the turn fin. not behind the sponson. continue to move the CG rearward until it stop submarining. it's not complicated.

[a53hoop]

sorry not reading carefull enough.not sure if i will get to try again this year as is really cooling off. tks al

[Peter A]

Maybe you need to try a different prop, something with less lift. Perhaps share more info of the boat set up and pics, may help us help you.