Discussion in 'Boats, Motors, Trailers and Towing Rigs Forum' started by paulo, Jun 12, 2018.
Pros and or cons for a stainless prop on a 115h pushing 20' aluminum?
Pros: manufacturer claims improvement in performance.
Cons: costs - costs of props and costs of repairs if you hit something. Aluminum is more forgiving than stainless and I'd rather replace the prop verses the bottom end
SS prop better hole shot, no dings on small impact items.
I wouldn't go back to aluminum after running SS.
I bent my output shaft on one of my boats that had a ss prop. No give.
On a lighter 20' aluminum, you will notice only a marginal improvement in performance with s.s. Its on the bigger and more importantly heavier boats where material flex is much lower in s.s vs. aluminum. The advantage of s.s is much less flex and due to the inherent strength of s.s it has a thinner profile so less drag through the water. On my nearly 2 ton Striper, I have s.s and love it.
get a stainless mercury prop with a conversion kit. The mercury props have a plastic insert that allows the prop to slip if you hit something and it will save your gearcase.
Stainless on my present boat for 26 years and not one gear case issue from hitting something. Probaly some luck involved I would think and not running in total darkness helps. When I did run aluminim I would get bent blades from running over bull kelp. Not big bends but enough to put the prop out of balance and be a long term issue for bearing wear due to vibration. SS for me...a polished stainless prop is engine jewellery too, looks better.
Appreciate the comments thus far.
Its sort of what I figure. About 50 - 50, more so with a bigger heavier boat. I was also aware of the flex factor and hole shot capability. That typically is reserved for greater current conditions like a river perhaps. Keep them coming and maybe there will be some advice or comment that may push me off one side of the fence or the other. Many thanks to all.
You will be in the prop shop a few times a year with an aluminum prop...just running over a small stick will require a repair...cheapest I know of to re-tune a prop is $95.00 .
Ymmv. I’ve run with an aluminum prop on my 22’er for 8 years. I average 150hrs per year on my main. I’ve only bent the blades three times. Once I bottomed out at low tide, another time I scraped a boulder during beaching, and the third time I hit a piece of cord wood that appeared out of nowhere. Haven’t had any issues beyond that. I’ve hit plenty of sticks.
I don't have too many data points to offer. Former boat was a 17.5' foot welded aluminum boat with a 70HP Yammy. From there I went to my current 16' fiberglass with 115HP Evinrude. Both with stainless props that took multiple hits with no issue.
That said, both came with 'upgraded' stainless props. Neither came with the OE props. For what that is worth.
Hi paulo. The choice might depend on how the boat performs with the current prop; do you reach max RPM and/or do you have cavitation issues, etc. If i were to get a different prop & had O/B power, it would be stainless as i believe that all O/B's are designed to use S/S props where some other drive types were not. A S/S prop can have a more aggressive cup placed on it. With a cupped prop, you get the low -end performance of less pitch, but also the top end performance of the "effective pitch" a cupped prop gives. The cup also allows you to run the O/B more out of the water creating less drag which has many benefits. I would contact Michigan Propellor for advise. Trim tabs will also give a performance increase.
" i believe that all O/B's are designed to use S/S props" Is this just your personal belief (in which case -- fair enough) or do you have corroboration? Just interested in case I am using something I should be ill advised to.
I'm thinking rubber props would be better for some people I know...
I've used an aluminum prop for many years. The performance of stainless may be slightly better but I have never had an issue with that or with dings except one rock strike at a harbour entrance. I replaced the damaged prop for $207, tax in. Stainless would have been much, much more. North Island Propellor will tweak or re-pitch an aluminum prop for about $80, if needed.
Are the newer, higher density aluminum alloys any better than the plain, older ones?
I have no performance issues with what I have now but always thinking of things to improve on. I am leaning towards leaving things as is. I'm out of the water and on plane pretty quick and on flat water I can trim out so I am doing 30mph with 4700 - 4800rpm. Good fuel economy as well. I never thought that changing was going to be a major improvement and with the feedback from this post I think it will be statas quo unless their is a screaming deal for a s/s prop.
All I can say is that when I ran aluminum I had repair costs...sometimes not for a long time and then one time twice in a month from hitting something I didn't see. Since I have run stainless...nothing. Touching wood right now.
Separate names with a comma.