SS PROP VS ALUMINUM

onthewater102 · Jun 23, 2016

Yeah I wasn't comparing time to get on plane between a 1436 and a 1648 but once on plane I should be lighter and displacing less water with less contact surface area & all other things equal should if anything have a slightly higher top speed due to less resistance to the prop making the slip ever so slightly less...if nothing else the same top speed. :-( I guess perhaps my through hull side imaging transducer is really making that much drag. But sorry - didn't mean to hijack your thread...

That's definitely the same 20hp carb throat. I would hold off on the new 13P prop b/c if you're getting full RPM's out of your motor with the 20hp setup you'll be able to turn a more aggressive prop (14p or maybe even a 15p) with a 25hp @ the same RPM.

onthewater102 · Jun 23, 2016

If you're not the original owner perhaps someone repitched the prop - that's also a possibility - you might already be running a more aggressive pitch & as the power output sounds sufficient to get it to full rated RPM's @ WOT. You'll know if you try the new 13P and go slower.

scoobeb · Jun 23, 2016

I have used the same prop twice believe it or not. The 02 25hp I have has the same original prop on it,same numbers and I switched them out and got exactly the same speed. I was thinking of going to a 14 pitch prop but I thought my hole shot would suffer some even know it gets on plane I mean instantly. The lower unit ratio is possibly what's having me be able to get this speed,it's 2.25 which is an awesome LU gear ratio imo. Funny thing is both mercs have the original props on them,the 93 I have has all of 25hrs of use since new,the old man who owned it used it for like a yr here in fl and passed away and it sat in storage for a very long time,near most of it's life,the guy I got it from was his son like 22yrs later,how crazy is that??? The 02 merc has 3hrs of use,never had a tank of gas ran through it yet and it sat for near 14yrs,it's like new except a few scratches ,I'm selling the 02 and keeping the 93 because I put a bunch of work into it,just maintenance stuff. It is I mean a sweet engine,both are so clean you can eat dinner off them,lol.

scoobeb · Jun 23, 2016

I just ordered a new 13 pitch Solas aluminum prop and I'm going to use the one on it as a spare,I may get a 14 pitch when I swap carbs out in the fall,I may do it earlier but will see. My buddy has a brand new 20hp Tohatsu, he has the same boat as me and he gets on plane a bit faster than me with a 4stroke believe it or not,he's also carrying 600 lbs of weight compared to my over 1000lbs,now granted his 20hp is just that as mine is off a 25hp power head so a big difference, he can actually get me out of the hole but in seconds I'm blowing by him and he couldn't believe how fast I caught up to him because he was a good 15ft ahead of me. I was totally impressed with the torque of that 20hp 4stroke Tohatsu, blew my mind. I have owned a new 20hp 4stroke suzuki as well and the torque on that motor is insane as well for a 4stroke. Keep in mind though,my buddy is running a 10 pitch prop so he should get me out of the hole because I'm running 3 sizes bigger but he was just amazed at how much power my 20 had to catch him. I was two. I get on plane in seconds,he gets on plane in like micro seconds if their is such thing,lol. These 4strokes are starting to compete a bit on power with the 2 strokes in amazement. Good to know our future for 4 strokes looks bright.

ericman · Jul 11, 2016

I'd say that an aluminum prop on a 20 hp is NOT flexing when under power. I'd also say that the only time a stainless prop really makes ANY sense at all is on a much bigger motor, used in deep enough water to avoid hitting anything with the prop OR in saltwater. If you hit anything with the stainless prop, especially when running a 20 hp with a 1/2" driveshaft, you will severely mess up your drive shaft, whereas the aluminum prop will bend or break, which is a much cheaper fix than a new driveshaft.