propeller issue - help needed

[berrypde]

hi folks

a friend is coming down to Trinidad and will bring the propellers for me..

I have 2 x 9,9 4 stroke long shaft Yamaha outboards. we cruise year around and the main problem are the plastic and/or aluminum original propellers we changed many times now, they tear easy and last not too long.

now I want to look for stainless steel ones but at same time want to know if anyone here has experience with those SS ones and what would be the best diameter/pitch election... so far we are ok with our configuration but want to see if we can gain some gas mileage...

our motor sailing cruising speeds are at 4 to 5,5 knots with 1 motor at 3/4 throttle and average conditions (always when into the wind of course). we spend 0,80 gallons regular gasoline per hour. the boat is a light displacement catamaran , 4,5 tons weight.

[colemj]

What do you mean by "tear easy"? Do you mean the blades rip off? If so, I don't understand how unless you are hitting the bottom or wrapping things with them.

If you mean that they are spinning their rubber hubs, then I don't think SS ones will help with that. It sounds like too much resistance (or hitting objects again). If this is the case, a lower pitched propeller would possibly work. I think Yamaha specifically makes a lower pitch "workboat" propeller for their 9.9 long shaft engines that are used as sailboat drives a lot. You cannot put a larger diameter prop on because the cavitation plate limits the diameter.

Mark

[GordMay]

Yamaha Aluminum "Dual Thrust" propeller?
➥ http://www.yamaha-motor.com/outboard...2.5-%20F20.pdf

[berrypde]

i'm sorry if my english is not accurate , its not my mother language... by 'tear off' (wear should I say??) I meant a rapid destruction, cracks , and bends, mainly because the debris that they catch.

We never touched ground with them. in 4000 nm cruising we changed 3 propellers sets by multiple reasons (nets, floating ropes and we almost damaged seriously the boat in a lock when we cached a rope), what I consider too often (maybe the solution to my problem would be to clean our oceans??? ).. so i want to try the SS ones... but they are not made by Yamaha, they are heavier and might destroy the transmission gear as well. instead to break the propeller it might destroy something in the gear box... i just want to share what my experience is and see if someone else has a good experience with SS ones.

BTW, the actual propellers are double thrust ones with an unknown pitch (i dont have it here to look at it)

the only yamaha aluminum propeller listed in their part list is the 6G8-45947-00-EL PROPELLER (3X11-3/4"X9-1/4"-R) UR ALUMINUM

there are 3 plastic types:
1. 6G8-45945-00-00 PROPELLER(3X11-3/4"X12-1/4"-R)UR PLASTIC DUAL THRUST
2. 6G8-45941-00-00 PROPELLER (3X11" X 11-3/4"-R)UR PLASTIC DUAL THRUST
3.6G8-45943-00-00 PROPELLER (3X11-3/4"X9-1/4"-R)UR PLASTIC DUAL THRUST

since i am not a tech guy and i need to purchase spare parts (not having the propeller here to see the part number) i would appreciate all the help i can get to buy the new ones... and as I said before, i would like to know whats the experience that other cruisers have with Stainless Steel ones, if any. maybe they are too heavy or too 'solid' and will transmit the shocks to the transmission gear instead to break.

i dont know the real reason why yamaha has deigned the motor with plastic one: to go down with the price (most probable) or to use them as a sacrifice piece when hitting something.

we are looking forward to make a long journey where i dont expect to get many Yamaha parts, so i want to put new propellers and use the actual ones as spares (i have 2 or 3 sets of old propellers on the boat).

thank you