Pump intake grates- thinking of trying something taboo

[gmtech16450yz]

$40 each. Pretty cheap to go back to stock if anyone doesn't like it. The other thing somebody could do is to just cut the bars out of ONE side. You should be able to tell a performance and noise difference by throttling back on one engine at a time while cruising or at WOT and comparing.

Here's a deal, if somebody wants to cut the bars out of one side to experiment and ends up hating it, I'll paypal them $40. lol. The difference in sound was pretty obvious for me and my wife, it would be nice to verify if the grates themselves are a source of noise in these boats. BTW, my '17 212 S has a TON of sound dampening work done to it, and it still made a difference. The whole inside bottom of my hull has extra sound deadening already. On a stock boat it could make even more difference. Or I'm completely wrong on this whole theory, that's entirely possible too. haha.

edit... $37 with free shipping actually...


(link to intake grate source)

 

[Scottintexas]

would you really have to sawzall them off ?? couldn't you just unscrew the whole plate to remove them whole,

if you were concerned about the transition into the tunnel could you just silicone everything smooth ?

wouldn't that be easy enough for testing purposes ?

( I'm actually curious about this )

 

[gmtech16450yz]

would you really have to sawzall them off ?? couldn't you just unscrew the whole plate to remove them whole,

if you were concerned about the transition into the tunnel could you just silicone everything smooth ?

wouldn't that be easy enough for testing purposes ?

( I'm actually curious about this )

Yeah you could totally do that. Obviously the silicone wouldn't last long, unless maybe you used 5200 but then that would be brutal to remove. You'd have to put the bolt in the front back in since I'm pretty sure it goes through the hull, I don't remember. The other advantage to just chopping the bars off is you don't have to disturb any of your sealing on the front or back if you have them put in with 5200 or similar. (I tend to err on the best/longest lasting sealing vs. ease of disassembly personally, but that's just me.)

It's cool to see some familiar names. it's been years since I've been on here.

 

[Ronnie]

@gmtech16450yz , welcome back.

I have a spare intake grate from a 2017 240 and am considering cutting the tines out of it to see if i get the same results you did, especially where quieting the noise is of concerned. I would make sure that I may remove the original gate before carving up an another one.

 

[Neutron]

I'm baaaaaaaaaaaaaaaaaaaaaaaaaaaaack. lol.

Ok I'm dredging up a 7 year old thread, but it's one I started so I figured it's ok.

I did end up taking those intake grates off just for kicks. I machined aluminum blocks to fit in the mounting spots so the tunnel was nice and smooth. The blocks at the back can be taken off easily, on the blocks for the front I used regular automotive fiberglass (bondo) to fill in around them so to remove them I'd just need to dig out the bondo. So it's a semi-permanent mod but whatever, I seriously doubt I'll ever put the grates back on.

So the results? One was expected, the other was a complete surprise. Removing the grates gained 1-2mph easy and the accel out of the hole pulls good with zero cavitation. But here's the surprise effect that was super obvious right off the bat... It's WAY quieter!

Ok so I noticed the sound difference the minute I first started the engines at home. At first I actually figured it was because when I painted the tunnels with epoxy paint, I put a light coating in the impeller housings too. It makes sense that the epoxy paint could quiet the impeller noise itself but after running it, any impeller/paint contact would have worn away. Out on the water it's absolutely noticeably quieter at all rpms and speeds.

So here's my theory, those grates were working like a lever on a drum. The noise created in the pump would transmit through the bottom of the pump, into those grates and then into the hull. The hull might be acting like a drum or a speaker in that area and that could be the source of a lot of the noise. Removing that lever/drum connection stops the noise transfer. hmmmmm. Maybe.

So for anyone daring enough to risk ~$80 worth of intake grates, here's an easy way to to this mod. Take a sawzall to them! Seriously. I enjoyed the challenge of making the aluminum inserts but honestly it would be way easier to just chop off the bars without taking anything apart at all. Just sawzall off the bars front and back, then use a grinder to smooth down rest of the bars on the blocks. If you decide you want the grates back, order a pair online and just put them back in. I believe you can get them for around $40 each if I remember right.

So who's gonna say "F-it" like I did and try it? The downsides? I suppose it's possible you might suck up something that the grates would stop, but honestly I'm not sure what that would be. The grates don't stop ropes, seaweed, rocks or small pieces of wood to be sucked up anyway. The other downside? Ok so there's a chance if the engines were running and someone swam UNDER the boat and reached their hand up into the tunnel, they'd get their arm chewed off. But again, it's a helluva lot easier to lose an arm on a prop boat so even with no grates, a jet boat is still infinitely safer in that respect. I mean who the hell is swimming around under a running boat anyway?

The upsides? I'm not guaranteeing any speed increases but I seriously doubt it could hurt top speed or performance, it has to help. Stick your finger under a running faucet and see what happens to the water flow. My theory is that those grates not only cause some amount of disruption, I'm also thinking they might cause some amount of aeration at high speeds/flows. And there seems to be a noticeable sound decrease, which is always welcome in these boats. Again, I'm not saying you'll 100% get the results I got, but who knows, you might be surprised!

Welcome back! Always love reading your mods. Any pics of the tunnels and intakes

 

[gmtech16450yz]

Thanks, yeah I definitely remember all your screen names as being some OG dudes. I probably did a few other mods to the boat since I've been on here but mostly I've been working on other projects. I quit my dealership job 7 years ago and have been playing, traveling and building chit nonstop since. My wife is now also retired so we've stepped up our goofing off to epic proportions. lol.

I only took a couple pictures, this is before and after I sprayed it...








Not too exciting.

These are from today...