|
|
Posts: 109
Location: Spencer, Wisconsin | I am looking at improving my top end and overall performance of my 90-4 stroke yamaha G3 V170 boat. The current prop is the alumimum 13 1/4 X 17 K and the top end is 35-36 mph at 6000 rpm. I've looked at several sites but really would like to know if i go larger pitch and diameter would achieve my target of low rpm and high speed or go smaller? I know i will need to go to a SS-prop to achieve my goals but which way?
Desired targets are 5000-6000 rpm @ 40-42 mph any suggestions on diameter and pitch?
Thanks
Edited by TET62 10/27/2007 6:16 PM
|
|
| |
|
Posts: 3518
Location: north central wisconsin | Greetings. I just bought the same motor and have been playing with propping for awhile now, and finally have it right. I traded a Merc 90 HP in for this motor and the dealer tried several props before settling on the like new SS that was on my old rig. This prop got me almost 40 MPH top end, but my hole shot was not the best. the prop is a 13.25X18 cupped Power Tech brand similar to a Vengeance. Oh, I run a Ranger 690 Tiller, so probably a bit heavier boat than yours..?..
That said, I was not able to get the rpms I desired either from the 18 pitch, as I only got 5300 RPM's which is not the best for a 4 stroke that should max at 6100. So... I ended up back at the drawing board trying more props. I finally orderred a semi cleavered SS from Power Tech(orderred from Precision Propellor in Brainerd, MN). The prop is nearly the same as the OEM prop for my rig, though slightly cupped. It is a 13.25 X16 and I just love it, am getting the hole shot i desire, and still getting 37.5 top end by myself.
I am not so sure that you will get 40 mph from your rig, but you'll need to go to a higher pitch if more speed is what you desire. Your hole shot will suffer a bit but I am sure you know that. Also, be sure that you can still get the rpm's you need. Not the best to top out at less than 5500 on that 4 stroke. Too much work for that motor if the case. Also worth mentioning is the fact that an aluminum 17 pitch will not perform as a ss in the same model. The aluminum will turn much easier, ie you'd need to go to a lower pitch to mainain the identical rpm's that you have on your aluminum, if you go to ss. Try a few props. Most dealers will let you try one, though you'll own it if you scratch it.
Lastly, I still have the 18 pitch SS that I tried to start with. I was going to keep it for a speed prop/spare, but it is just too heavy to keep along all the time. I'll probably sell it and get an aluminum 17 pitch for a spare. If you are at all interested in trying it, let me know. |
|
| |
|
Posts: 109
Location: Spencer, Wisconsin | Hello,
Thanks for the insight and your experiences regarding your quest for the same "more performance". The dry weight of my boat is 1,100-1,200 lbs a bit heavy minus full tank and me but a very nice ride and performer. After reviewing your trails with your boat maybe the 40mph quest maybe a stretch for mine. I did not know with the 4-stroke that less rpms is not good, a lesson learn'd before a major mistake.
During the summer it just seemed the motor was hauling but the boat wasn't it was like the prop was not cutting the water is was just pushing through myabe its me but though a SS-prop would hold up to the torque and flex. So, your opinion to balance both the hole shot and a decent top end if i were to chose a SS-prop the 13 1/4 X 15 might be the trick? My alumimum prop from the factory is the 13 1/4 X 17. To your point going to the larger prop like your spare may not be the way to go for me ie; less rpms and risking motor damage. So your factory prop vs. your SS-prop you said are nearly the same is the difference was it the pitch that was smaller slighly?
Thanks
Edited by TET62 10/28/2007 8:49 AM
|
|
| |
|
Posts: 3518
Location: north central wisconsin | My new stainless prop is a 16 pitch vs. 18 pitch that the ss Merc prop was. The older prop was cupped also. If my boat was a bit lighter I'd be running the old prop. If you want more speed, and are running a 17 pitch al. now, I wouldn't go with a 15P SS. You'd probably not gain much other than a $300 bill. Go to a slightly higher pitch and see if you can maintain your RPM's and get a bit more speed. you might want to have a dealer attach a digital tach as well. not saying yours is off, but mine was reading a bit low, so my RPM's are/were actually closer to where I wanted them than I thought. I can over rev my rig right now when it is naked(empty). She runs perfect with two guys and gear at WOT throttle which is what I wanted. Again, I was looking for more hole shot, so I dropped a pitch or two. the other prop really hauled the mail, but took a bit longer than I cared for to get up out of the hole. Again, if you'd like to try my other SS on your rig, you are more than welcome. Sounds like it could be a good one for a rig of your size(mine is much heavier than yours). You'll just need a yamaha hub kit for it(about$40). Drop me a PM.
Edited by Reef Hawg 11/4/2007 7:33 PM
|
|
| |
