Rehub the bloody thing EVERY year.....

[zkimball]

I'm turning a P17X15 (or 15X17P) Viper with a '98 150 Johnson. I have to rehub the thing EVERY SINGLE YEAR! I spun it again while on vacation in the Keys this year and it left me on the beach for three days. I switched prop shops, had it done again, and it spun the second day out! I went back to my old prop shop, explained the problem and asked for help. They said the problem was probably too hot exhaust from my engine. Hmmmm......?

Sound right? Wouldn't too much heat cook my engine before my prop in the water? Has anyone seen this before? Thanks! Z

 

[jimmbo]

Re: Rehub the bloody thing EVERY year.....

Almost sounds like the ID of the hub is a bit too big. Never seen it before but that doesn't mean it can't happen

 

[Dhadley]

Re: Rehub the bloody thing EVERY year.....

That's very possible. What are you running for the little torque tab above and behind the prop on the underside of the AV plate?

 

[steelespike]

Re: Rehub the bloody thing EVERY year.....

I do seem to remember a thread here regarding exhaust heat damaging prop hubs.Don't remember the brand but it seems it was a 4 stroke.It also seems there was a factory fix.perhaps a search will turn up something.
If I can recall this with my terrible memory someone out there must remember.
I don't recall if it was in props or elsewhere.

 

[Dhadley]

Re: Rehub the bloody thing EVERY year.....

It can happen with any drive with thru hub exhaust. It's kinda common on newer "green" motors. There are several fixes, depending on the cause, but we have to start with the basics. The first thing we need to know is if the stock torque tab is in place. Or if it's not a stock one.

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

I've been playing with these things for 30 years, but I cant say that I know what a torque tab is. Are you talking alout the zink lateral trim? Z

 

[dreamchaser]

Re: Rehub the bloody thing EVERY year.....

Z, What Dhadley is referring to is ur torque tab, located as he says directly above the prop, mounted to the under side of the ventilation plate. part number 338742 .

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

Sorry...I've always called it a trim tab. I juess torque tab shouldnt have been such a stretch for me.

Yes! I have one mounted and it appears to be a standard issue 338742. Z

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

What's the trim (torq) tab have to do with how hot the exhaust is? Z

 

[Dhadley]

Re: Rehub the bloody thing EVERY year.....

OK, pull the tab off and you'll see a small water passage in it. There's a small hole in the fin that leads to a passage. Make sure that passage is clear. Then blow air into the passage in the gearcase to make sure it's clear. When you're running water goes in that passage and is channeled back into the exhaust to help cool it.

There could be other issues too but let's start with the easy stuff.

Have you tried a completely different prop? If not I migh suggest getting one and keeping this one for a spare. At least you wouldn't be high & dry if it spins again.

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

My plan exactly!! I have my eye on a Turbo OS1. I just got the Viper back from the prop shop and I'll pull the tab tomorrow when I put it back on. I have to run it again to confirm my numbers at WOT.

Thanks for all the help! Z

 

[Texasmark]

Re: Rehub the bloody thing EVERY year.....

Are we talking about a rubber hub or the newer replaceable plastic ones?

Mark

 

[Dhadley]

Re: Rehub the bloody thing EVERY year.....

If it had to go to a shop to be replaced it'll be the old standard rubber hub, not a T-Lok or Flo Torq system.

 

[Dhadley]

Re: Rehub the bloody thing EVERY year.....

Ask the prop shop about the condition of the inside of the hub. Everytime they press the old (spun) one out they have to clean the hub. They most likely do that with bead blasting. Since they know you've had an issue with hubs they should have inspected the hub area to verify it's still in spec and not too big.

There are different hubs too. I forget the part number but there is one that should be used when repeted spinning has been an issue.

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

Thanks for the replies! It's been raining all day for the last week here in Jacksonville and the river is way over my bulkhead and up in the back yard. I saw Dorothy and Toto this morning on the way to work..... I'll check it out this weekend if it ain't rainin' Z

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

OK! We pulled the trim (torque) tab off and the hole was open, as was the passage in the engine. All these years and I didn't know that little hole was there....

So..., is it a water intake? Does water enter there and go up to the exhaust port below the powerhead? If so, why? Why not just route some of the water coming from the block/heads down through the exhaust? How does this thing work and how do I tell if it's responsible for cooking my hubs?

Thanks for all you teach! Z

 

[Dhadley]

Re: Rehub the bloody thing EVERY year.....

If it's open it'll add water into the exhaust as it exits the midsection. That's all it needs to cool down slightly. If your prop shop can't answer the questions about the hub then I'd look at getting another prop. Obviously you need one as a spare anyway.

 

[zkimball]

Re: Rehub the bloody thing EVERY year.....

Gonna get an OS1, but I still want to know about the hot exhaust thing. I know the newer props need a different type of hub that uses plastic rather than rubber, but if my exhaust is too hot for one, will it not efect the other?

I had my assistants (16 year old twin sons) pull my prop off and instructed them to put all the hardware back on the shaft. It seems the retainer and the cotter pin didn't quite make it back on and now we can't find them. (Same way I learned!) I've been in Gainesville for the last two days, so I'll have the WOT numbers as soon as I can get the parts.

Yes, the Viper will become my spare. Z