This is the second time this year I have checked my intake and found three of the four bolts that hold my intake grate with the heads popped off. I know what would happen if the last one would break and that would mean the boat would make a very sudden turn most likely without me in it. The last time I thought they just worked loose and broke so I put lock nuts a safety wired them.
Apparently that was'nt the answer. I am using 5/16" SS bolts. Should I go to 9/16"? I did notice that the plate that bolts to the pump is not flat. It looks like it warped when it was welded. If I lay the plate on a flat surface I have about a 1/8" gap on each side. I guess that could be part of the problem but I realy don't know. I appreciate any help you can give me on this.
[img]http://free.***boat.net/gallery/Reader_Rides/Jet_Boats/intake2.JPG[/img]
The problem isn't the diameter so much as the material. Switch out to a good grade 8 black oxide coated fastener and see what happens. You'll need to get under there every so often and see how they're fairing against rust, but they should be more than strong enough. Stainless just doesn't posses the shear strength you need.
Good luck
Chris
First i would get rid of that grate. They have much better ones now, and drill and tap the bolts threw and add nut the bolts on the inside. Thats how its done at the track.
wink
I had this problem also. I would take the advice and thru bolt as many as you can, if you can. The other thing I did, was, is the bottom end that goes into the intake does not rest on the bottom of the suction piece, weld an ear or 2 so it hits/rest on it. This way the presure can't pull it down.
Later
MikeC
Uh, not to be a smart ass but I think you answered your own question. 5/16" bolts should be fine, flat broke's suggestion is a good one but fyi I've been running stainless steel hdwe for last five years with no prob, set up the way SilyDevil described. Invest in a new loader grate.
flat broke:
The problem isn't the diameter so much as the material. Switch out to a good grade 8 black oxide coated fastener and see what happens. You'll need to get under there every so often and see how they're fairing against rust, but they should be more than strong enough. Stainless just doesn't posses the shear strength you need.
Good luck
ChrisFlatbroke has the right idea. I thru bolted mine on my race boat. I check mine after every run. Every so often will should be fine on a lake boat.
Flat Broke.. They did shear off thats for sure so I will get the harder bolts this time. Thanks..
Sily Devil.. The bolts were threaded all the way with loc nuts on top. The grate is a copy of the original that came with the pump and intake when the boat was build back in 77. The frist grate broke at the welds on the plate when I was doing a little speed run with my buddy in 78. I did'nt think we would ever stop skimming across the water after the boat made that quick turn. But we did and luckly we both came out of it with just a few bad bruises. I garaged the boat after that untill last year. The pump and intake were by Hallcraft and alpha marine. I guess the grate could be outdated sense it is 25 years old. It has run 104 with that grate though. How would a newer design help? More out of the hole, More top end? Will it help hold the boat down at high speed? What would be the benifits of a new grate?
Thanks for your help....Hal
Mike C.. Very good idea. I had'nt thought of that but I can see the benifit of bracing the back of the grate to keep the stress off the bolts. Thanks...
I guess I'll go see Greg about a new intake also.. Thanks for all the help everyone.. Hal
Yep, Chris's right. Some SS poor quality, even better SS maybe not as strong as black oxide. Had my SS break, switched to oxide...same diameter. No more problems.
[QUOTE]Originally posted by Hal:
[QB]Flat Broke.. They did shear off thats for sure so I will get the harder bolts this time. Thanks..
Harder bolts will have even less shear value than a softer bolt. Harder= britile Softer=More elastisity(sp?)
Just my .02
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