Poly/UHMW intake fins?

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rotus623

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Hey guys does anyone know of a place online that I can order UHMW intake fins? I live 15 minutes from James River Jets, but he said the guy who makes/supplies him with the fins is in Florida and it could be weeks and weeks before he gets more in!!!
 
I've had them on a jet boat without a tunnel and I was not happy with them. They are very thick (about 1/2" as best as I can recall) compared to the steel fins and are installed with soft stainless all thread rods and if you hit anything with them, the fin will fold upwards and bend the rod. This will enlarge the mounting holes and once that happens, it's almost impossible to keep them on straight. They are cut back to fit up against the both the bottom and side of the intake and they will slip up and fold out once the holes are deformed. They might work better on a tunnel boat where you won't be as likely to hit bottom.
 
Larry, thanks for the feedback. This is the email that I got back from OBJ


Hello Peter,

We always recommend a set of intake fins for a tunnel hull to reduce
cavitation.

Anyways, I hear your pain about the grate pins and intake housing. I just need to find a way to stop cavitation on hole shot!!
 
If you put the fins on your intake, I strongly recommend either the steel kit from OBJ or you could have aluminum fins welded on your intake for about the same cost. The link below will show you what the welded fins look like.

https://www.wooldridgeboats.com/store/equipment/jet-foot-intake/jet-foot-intake-large-intake-with-fins
 
how do the outboard jet ones mount any differently thought they just used some threaded rod as well seems like they would wad up just as easily.
 
handyandy said:
how do the outboard jet ones mount any differently thought they just used some threaded rod as well seems like they would wad up just as easily.

The steel used in the OBJ rods is a lot harder and they are only threaded on the ends. They will bend if you hit something hard enough, but it takes a much harder hit to bend them than it does the all thread rod furnished with the UHMW fins.
 
rotus623 said:
So Larry,

Would you say the best of both worlds would be the rods from OBJ and the fins from JRJ?

Actually, I wouldn't. The way that the UHMW fins are made is a poor design. I really don't know how to explain it so that you can visualize them other than the way I did in my first post in this thread, but I saw in one of handyandy's posts that he has a pair of them on his motor. Maybe he can post a picture of them so you can see how they are made.
 
If your boat is set up right you shouldn't need one. The Russians are generally using inflatables with tunnels.
 
I have the UHMW intake and fins I don't always run them. Depends on what I'm doing. The UHMW intake is well made did slow me down some not a lot. I like the fins they haven't taken any good hits yet. I'll try and take pics of the fins and intake to show how they are. I do want to come up with a better way to mount the fins the threaded rod from james river jets is crap. I may have to call obj and get their rods and maybe make plate that disperses the clamping force of the nuts tightening down on the fins. What would be awesome is if rock proof made their intake with fins so it was one uhmw piece with fins. I like the fins cause I can run my motor a little higher out of harms way.
 
I need to find some time to try and do a little cleaning up and smoothing of the UHMW intake to see if I can improve it's performance some.
 
I have a fresh set of OBJ intake fins, new grates and a nice gently used impeller (Thanks Larry!!) that are all awaiting trial!!!

Hopefully I will put the impeller and new grates on and take her to the river this weekend. If she dont cavitate and runs well I will lift her up one hole and install the intake fins and see how she does. Jim at OBJ told me I could afford another hole up with a new impeller and some fins. May even take the motor hoist to the riverside with me!!
 
handyandy said:
I have the UHMW intake and fins I don't always run them. Depends on what I'm doing. The UHMW intake is well made did slow me down some not a lot. I like the fins they haven't taken any good hits yet. I'll try and take pics of the fins and intake to show how they are. I do want to come up with a better way to mount the fins the threaded rod from james river jets is crap. I may have to call obj and get their rods and maybe make plate that disperses the clamping force of the nuts tightening down on the fins. What would be awesome is if rock proof made their intake with fins so it was one uhmw piece with fins. I like the fins cause I can run my motor a little higher out of harms way.

A place called Top Notch Machining used to make them. I bought one back in early 2014. Best I can recall it cost me around $350 plus shipping. It lasted about 15 minutes on my boat. I hit a submerged tree and it ripped the fin on one side about halfway off. If it had been an aluminum intake it wouldn't even have been damaged. They were good enough to refund my money, less shipping of course. They must of gotten a lot of complaints because soon after that, they started recommending that they not be installed on non-tunnel boats. They have stopped making them completely now. I don't have any pictures of the intake before I hit the tree, but I do have a couple of "after" pics.
 

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dang surprised it did that off a tree that sucks at least they refunded you. The rockproof ones have a lot of stories of taking good hits. I haven't subjected mine to any bad ones as of yet. I haven't run it a ton either I throw it on for certain places I go once in a while where I know hitting rocks is inevitable. If my poly fins don't last I might have to take stab at making my own heavy duty stainless or aluminum ones. Wish we could get those rubber russian ones they look pretty good videos of them taking good hits would be interesting to try one.
 
Ok guys, figured I'd give you all an update here.

I ended up going with the OBJ fins and couldn't be happier!! I didn't seem to lose any speed. I have lost all cavitation on hole shot (even though the new impeller seemed to solve that), and in a pretty decent chop the motor didn't cavitate at all!!

The biggest thing that I noticed was that I can turn this boat as HARD as I possibly can, and it will NOT cavitate. Excellent!!
 

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