Sport jet 90 - 120 intake grate streamlining?

[RedBarron55]

Now that I have mu boat running with the Franken-Grate

That hangs down into the water stream a pretty good bit.
The boat speed is not as fast as the original tests say it should be .
I got 32 MPH at ~5000 rpm where the 1995-6 tests gave a speed of 38 MPH with the poling platform and two people, 40 without the platform.
I think that the stock grate might be faster (while I don't need a lot more speed in the chop in the Santa Rosa sound)
I have a stock late model grate (1996) I hope will fit or can be modified since the pump housing is the same P/N.
My question is if before I install it is there anything to be gained by smoothing or streamlining the grate bars?
I don't think I will have a problem with stones here in the land of sand.
As an aside I have no idea of the heritage of the grate I have and perhaps it would be worth 6 mph it it were more weedless or sucked up less sand in shallow water.
I think if you ran over a sandbar the dredge effect would pack the pump full of sand, however.
Any experience with streamlining or modifying the 1996 grate of what the fitting to an older jet (1994-5) pump?
As a second thought you can see that there is a slight depression all the way around the ride plate is there any advantage to filling and smoothing with some RTV or other filler?

Pay no attention to the old, bald guy in the lower left of the picture!

 

[Cobra Jet Steering LLC]

I always sharpen the leading edges of my intake grates

 

[swatski]

I always sharpen the leading edges of my intake grates

Now you are telling us!

I did mine after @gmtech16450yz published his intake mods. I would say a definite improvement in pump loading.
https://jetboaters.net/threads/pump-intake-grates-thinking-of-trying-something-taboo.15594/page-2

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[Cobra Jet Steering LLC]

Actually there are several things I do to the intake grates day one because of the weed issue here in Tampa bay, prior to doing these mods I would need to constantly stop or jump waves or do the reverse move to get the weed out. My mods do an excellent job of reducing but not totally eliminating the weed issues. But even when weeds do manage to get on the grate I know they are there but they do not cause me to need to stop. I have a list of items I do from the beginning learned from past decades of boating.

 

[RedBarron55]

Jeff can you post some pictures? Or perhaps tel us what you d and the results.
We don't have a bad weed problem here in Navarre on the sound, but since I haven't gotten FrankenGrate off yet I have time to work on the late model grate I bought.
By the way I feel better about my speed with FrankenGrate since I looked at the phone GPS speed app that recorded the track and max and min speeds.
The thing was set to knots instead of MPH so the speed was 32 Knots or about 36+ MPH.
That is just 2 mph off of the 1996 test and may be more accurate then their test.
When I go the the trouble the unscrew, break the heads off and drill out and tap I may try doing a better job of streamlining the blunt edges left on Frank.

 

[RedBarron55]

Whaddabout the trailing edges?
I would think that making a streamlined profile on both sides would help.
When I get the FrankenGrate off and the holes retapped and repaired I will Smoothing the plates etc to help move water in.
Would a better pickup load the engine more and reduce rpms or feed in higher pressure water and reduce the rpms?

 

[Cobra Jet Steering LLC]

get one like this it is for a 90 or 120 hp they are available on e bay I believe

 

[RedBarron55]

I bought one off of eBay for a 1996 the latest one.
I don;t know it there is any difference in that one and the one that came on my boat, but the pump housing part numbers are the same so I assume that I can make it fit.
I was wondering about any useful modifications before I install it after I remove FrankenGrate and fix the mounting holes I know I will have to drill frozen, corroded screws from.
So far I have one removed, one head broken off and one that the Apex Phillips bit broke off in.
WHo knows Frank might be better (or worse), but I have the new stock grate and trying stuff keeps a retired guy busy.
By the way the grate in your post is the older one I think and the newer one has a little different shape in the inside front. the "upper roof" goes further back, perhaps for better flow?
I can't think why Mercury would design and incorporate a worse working part so who knows?

 

[Roger Ski Gapinski]

Hi, I was wondering if anyone knows if you remove the impeller grate and/or ride plate on 1996 Regal Rush XP 120 jet boat will you be able to see the thru hull connector that the gate control/shift cable goes through? Mine broke a few days ago and I’m in the process of loosening the Phillips screws (6). 2 are really stuck even with my impact screw driver and PB spray.
Any help is greatly appreciated!
Regards,
Ski

 

[RedBarron55]

Haven't been there yet, sorry.
I had the ride plate and grate off, but I didn't look at where the cables come through.
The installation manual should show a bit about it though.

 

[Roger Ski Gapinski]

Thanks for your reply RedBarron! This morning I will look closely at the side foam exhaust seal. When I took a close photo of the OE serial number and hole where the cable enters I noticed there may be enough room for a new fitting if I pull out the seal at the top. If so, I will take a 1/4” plastic rod and insert until it reaches the thru hull hole. I’ll then slide a new fitting on the rod with a string attached to it. I’ll insert the rod again, pull the string through the hole and gently pull the fitting through the hole.
I’ll take some photos and update afterward!