What prop?

[matt12002000]

Have got a yam f80 4 stroke on a 5.3m tornado. It's a new to me second hand engine that came off a larger fishing boat. It had its first outing today. The engine revs to just over 6000 rpm flat out with no trim. The current prop is 15.5 X 15-k.

I have been told that this engine should rev 5600 to 5800 rpm. And one unit increase on the pitch would bring the rpm down about 300.

Is this right?

Would a 15.5 X 16-k be the right one?

[jeffstevens763@g]

Will that be the high thrust engine since it's off a fishing boat

[matt12002000]

That I wouldn't know. How would I tell? It's a 2003 engine I think.

[jeffstevens763@g]

I might be wrong but I had a quicksilver 500 with the high thrust yam engine the pitch & diameter were pretty close same as yours.
As a comparison my rib had a 90 Suzuki with a 14 x 19 prop running at 6000 rpm an inch in pitch is equivalent to 200 rpm I put a s/s prop on 13.5 x 21 more or less same rpm.
The high thrust has the bigger gear ratio ideal for the Heaver boat worth checking out with a dealer you might be able to go up a few inch on pitch depending on what your using it for.

Cheers

[jeffstevens763@g]

Just had a look the high thrust only goes up to 60 hp (T60) so it looks as though you could go to a 15.5 x 17 bringing it down to 5600 rpm.

[matt12002000]

Thanks for that. When I open it up from a standing start with the existing prop it is a bit too vicious really. If not dangerous. I think the 17 is going to be the one. An evening on the Internet it is!

[jeffstevens763@g]

When I bought my yam 60 the prop it came with was the same straight to the rev limiter from memory I went up two inch on pitch taking it to 5900 rpm but I did have a few props to try from the dealer on the Isle of Man.
Having had a look on the yam site and one other I think your 15.5 dia has certantly been propped to give thrust it looks like a 13.5 should be on it I would talk to a yam dealer before spending more cash

Cheers

[matt12002000]

Gone for a 13.25 x 17k. It would appear the 15.5 diameter was wrong.

[jeffstevens763@g]

yep the motor was propped for the heaver boat anyway sorted now hope it gives you what you want Matt.

cheers