sheikman1

Has anyone done any modifications to there silent thunder swim platform to relieve back pressue. I saw a thread that said you could drill additional 3" holes beneath the platform on the radius that goes from each side to side. I am wondering how much the silent thunder affects the performance of the motor.

sheikman

Iggy

I read someplace here that Formula did extensive testing and found it didn't hurt performance at all.
Most of the modifications done are to the internal baffles. Specifically removing, or taking a hole saw to, the one that's visible looking inside from the rear.
I found that one of the baffles in mine has come loose and should be easy to pull out. I'll have to look at the other side and see what that one's like.

RUSSSR1

It will only be louder when the box is in the water. On plane = no differance.

Rambunctious

if your plugs are in the bottom of the silent thunder then i think it will be louder on plane too. because the exhaust doesn't have to blow under the baffle plate through the water.

i removed my baffles last year. sounds better all around, although noticed more at idle. still has the "flowmaster chamber-like" sound of formula though. I like it.

do a search for my post on it here on the formula page. i even inserted a section drawing to show how easy it is to remove (ie cut away)


all it is is one fiberglass plate "glued" in on the top and two sides with a 1" gap to the bottom of the chamber. the chamber fills with exhaust water, and the exhaust is forced through the water and under this plate.
i used a sawzall and they were done in 5.75 minutes!!!! well 15 minutes anyway I cut a doghouse opening arch from the bottom right up and around to the bottom left of each baffle plate, then broke the piece in half to remove it out the square exhaust opening.

you need a long sawzall blade to do it though. sorry if you know this already. i did not see any speed increase. but is sounds faster

BUSTNOUT

Does anyone know the impact of taking out the 4 plugs on the underneath side of the swim platform? Will it make it louder?

Rambunctious

Mine are out. bought that way
don't know how much louder, but the water can't fill to the top of the sqaure exhaust tip and run out as designed when they are removed. supposedly they are deisnged to be removed when winterizing ( ie drain the water)

in the driveway, the water runs out the holes fast enough to not fill the chambers completely as designed.

mopower

Bustin,
Probably so The four plugs hold water in the "mufflers". By removing them you allow water to drain while on plane. At an idle they we stay full and quiet. Keep in mind even though the drains are open , you still have a constant supply of water from the exhausts.
I got mine three years ago without plugs and never gave them a second thought. Simply because when you pull it out to go home , you're carrying around more weight and I couldn't be bothered pulling them all the time.

BTW , Once on plane it does seem to get a little "throatier" but not to the point you have to SCREAM at the person next to you

Rambunctious

hey guys

we shoud invent "select Thunder" ( i trademark that right now.....)

it could be a pneumatically controlled flapper that replaces the fixed one inside the silent thunder. use it just like silent choice. only integrated into formula's system.

open for on plane. closes adn partially submersses into the water resorvoir for idle, could actually be designed for more back pressure because you use it mostly at idle

hmmmmmmmmm

boiler daddy, what do you think.....

sheikman1

I can't believe that you said that. I was just thinking about doing this to my silent thunder this morning.
Good job

sheikman 540

Rambunctious

I'll put you on the patent


the hardware exists, just bolt the flange of a switchable tip to the baffle plate instead of a transom