aluminum propeller advise

[duknut51]

We have a 09 Seaark xv180. When I bought the boat the dealer told me that i could expect 43-47 mph with the 08 90 hp Yamaha I had from the other boat that I had sold. With the engine set in the third hole down from the top, where the dealer told me to set it, the boat would porpoise at three quarter trim. The best I could get out of it was 39 mph with the 13.25x17 Yamaha aluminum prop at 5400 rpm and it wouldnt pull my 13x19 Yamaha aluminum very well. After reading several threads here I bought a 13x18 mercury vengeance prop from ebay. I also decided to move the engine up to the top hole. Here are some of my numbers and some pics.
The boat weight is 905lbs dry
mercury prop 3000rpm 24 mph
4000 33 mph
5000 42 mph
full trim 5500 45 mph

Yamaha 13x19 3000 rpm 22 mph
4000 30 mph
5000 38 mph
5500 43 mph
I didnt take time to do a full test of the 17p that I have as it was cold but it run around 40 at 5500 rpms. I had no venting issues with the merc prop in turns or trim it performed very well. The 19p I could vent in hard turn above half trim and it would loose grip and the engine would turn 6100 at very high trim angle, above the angle my gauge would read or above the point when the engine hits the two short cylinders. The bottom of the tape that I put on the boat is where the very bottom keel strikes the engine and the black line is where flat section hits the engine. I am doing all this to ask what would be my best choice for an aluminum prop, is my engine to high short of buying a pressure gauge and to help others.
Sorry for the long winded post. Kelly

 

[reelnative]

Re: aluminum propeller advise

Hi it looks like you have your motor mounted too hi but if it runs good like that then leave it, as to the props it sounds like the 18p is running out the best, the 18p is a sst prop I take it, if you go to a alum prop it will drop your rpm a little bit, I would stick with the sst prop if it were me tho

 

[duknut51]

Re: aluminum propeller advise

Thanks for the reply. The stainless prop is the best with the motor set this high for sure. I was a little sceptical of the engine being this high as well but when I bought the boat last year the dealer i bought it off of said to set it in the third hole down, one lower than it is now, and too use a 13x19 turning point hustler prop. Well I had the yamaha 13.25x17 so I thought i would try that first as it worked well on my prior boat and I had a hustler and it didnt do that well with my other boat when I had a 60hp on it. So earlier in the year I started making some phone calls and trying to get some info from some seaark dealers about this boat and I had two of them go so far as to say that they had went as high as 3.5 inches from the bottom of the boat to the center of prop shaft mine measures 4.5 inches I think they were running a mercury though. I may do the the one hole down with the 19p yamaha and the sst prop and see what that does. I guess I want to use an aluminum prop for snagging because there are times when you do a alot of forward and reverse if you get hung up and that back and forth with a heavy sst prop seems to be hard on the lower unit to me. thanks again.