Replacement prop questions

Ovey · 27 April 2014, 13:38

Hi guys, I've just bought a replacement prop after "dinking" my previous one. Having been happy with the previous I've gone for the same like for like that was on (13x19k). Does anyone have any recommendations for the grease to use when I replace it?

Secondly, more out of interest really, with all the talk about WOT being 5000rpm and giving 40knts (or whatever the recommendation/result is) - is the only way to measure this to give it WOT and measure the rpm (and speed)? I've not had the opportunity to give it WOT since I bought it in October due to sea state, weather, speed restrictions, etc. so I was wondering if I had to wait til the "perfect day" to get the info.

Thanks.

Sent from my iPhone using RIB Net

spartacus · 27 April 2014, 14:48

Any decent marine grease will do. I used to swear by Duckhams marine grease, but struggle to find it these days. Quicksilver or Starbrite would be fine. Clean off the old grease first. Remember and renew the stainless steel split pin when replacing the propeller and don't over-torque the castle nut.

Regards WOT, then yes, a relatively calm day is required to get full throttle over a decent distance to see what speed you hit on the GPS, you can adjust the trim, etc. The F115 rev range is 5,300 - 6,300rpm. However, there will be a lot of variables with other people's top speed results even with similar engines, such as different hull types, how much fuel on board, number of people, kit, etc.

Get the other propeller repaired. Can recommend Steel Developments for a first class job. http://www.steeldevelopments.net

Ovey · 27 April 2014, 15:21

Thanks for that. I think it makes sense to repair the old prop and keep it as a spare.

I've already received two new split pins so was just after the grease in order to crack on really.

Sent from my iPhone using RIB Net

Wibs · 27 April 2014, 17:53

Spartacus.....

When you say 'don't over torque the nut'

What would be the issue if you did.? I've recently changed the prop on my outboard (Suzuki DF50) and after it's 1st trail run I noticed a slight noise at 1500/2000 rpm.

Prop slip was an option but shortly ruled out, but I still removed the new prop just to check if I had assembled it correctly.

Trouble is.....with the correct torque, it sits right inbetween the split pin hole.!

Do I go more or less, I DID go less, and IMO, it felt loose, not too far off finger tight.!

I've now gone tighter, needed to use a block of wood to stop prop spinning etc....

Can you see any problems?

Sorry to hijack thread.!

James

Ovey · 27 April 2014, 18:55

That's fine, it's relevant!

As I understand it you go tighter if the hole doesn't line up - there are a number of "how to's" on YouTube which seem to be useful.

Sent from my iPhone using RIB Net

Dan Gurney · 27 April 2014, 20:12

I do mine up finger tight then go on to the first available hole for the split pin. As long as there's no play in it 'fore and aft' then I don't see what advantage the extra tighteness gives you. Having said that I don't really see the danger in over tightening either other than not being able to get the bugger off!

jyasaki · 27 April 2014, 20:32

You may force the thrust washer on so hard that you can't get it off. That said, I've always gone tighter than looser. And I always need to block the prop with a 2x4 to remove or install.

The grease is there to help keep salt water out from the spline set; if it dries and crytallizes in there, you'll have a tough time getting the prop off the shaft.

jky

Ovey · 13 June 2014, 22:13

I took the boat up to a WOT test during the week, with the new prop on. It's the same prop that was fitted when I bought it, just with less dinks in it! I got 33knots at 5200rpm.

So I'm guessing I need a smaller prop (to give faster rpm) and a higher pitch (to give faster speed)? Is that right?

Sent from my iPhone using RIB Net

solent spence · 14 June 2014, 00:23

Really you need to try more props to see what gives you what you want. Lower pitch will up your more wot revs and probably nudge up your top speed. Stainless prop blade shapes dramatically change hull attitude, planing speed, mid range etc.

Nick Hearne · 08 July 2014, 21:16

Quote:

Originally Posted by Ovey

I took the boat up to a WOT test during the week, with the new prop on. It's the same prop that was fitted when I bought it, just with less dinks in it! I got 33knots at 5200rpm.

So I'm guessing I need a smaller prop (to give faster rpm) and a higher pitch (to give faster speed)? Is that right?

Sent from my iPhone using RIB Net

Hi my 6m ribeye with the Yam 115hp with the same prop 13x19k I see 6100 rpm and about 38 knots as far as I know the prop has not been altered so it seem strange you are only seeing 5200 rpm???

Ovey · 08 July 2014, 21:25

Hi Nick, thanks for the reply. I think I need to re-test as it's been in for a service (found a blocked injector) and should now be different. I took it out on Saturday & it felt much more responsive although I didn't get it up to wot as it was a bit choppy. (I did go fast enough for the harbour master to blue-light me & have a chat though

)

Sent from my iPhone using RIB Net