aluminum prop comparison

[MBAKER]

Between different manufacturers do most props of a given size/pitch act the same or are some better than others? Do certain manufacturers have things they prioritize over others? I am looking at changing pitch and have run the following in no certain order just what happened to be available but if I change pitch I want to know what I am comparing and/or stay within a given manufacturer etc. I am currently running a 18P but with lighter loads than in the past and feel under propped now and easily run to 4800 with throttle to spare. (20' open bow 5.7 alpha 1) It is 4 blade for the low end pulling but not against going back to 3 either. Trying to decide about bumping to 19 or 20 pitch 4 blade, or 19 or 21 pitch 3 blade but if different props act differently I want to take that into account.

Michigan?
Powertech?
BS Pro?
Mercury?

 

[cyclops222]

How about Propellor Efficiency ? The most important fact about any propellor ?

 

[airshot]

All your numbers mean nothing without knowing the max rpm rating on your motor and the current max rpm of each different prop at wot. Numbers need to be accurate, not estimates. Even before that, is the engine running at its peak ? Mounted the right height and properly trimmed to get the correct readings.??

 

[Stinnett21]

Even within the same manufacturer when you switch prop families, e.g Mercury Vengeance to Mercury Tempest Plus, you cannot count on them acting the same. I've not experienced this but some report that that two, what appear to be identical props, taken right out of the box will often not run the same. It is best to find a prop retailer that will work with you on letting you try before you buy.

 

[MBAKER]

I guess I was just looking for general thoughts about different options or brands compared to each other and what other's experiences were with each more than anything. In my experiences with this same boat over the last 15 years the way we are running now it feels under propped on top because I have to hold back throttle more than I remembered but pulls well on bottom. Since we rarely ever run over 3500 for cruising anyway I may just leave it and not worry about it, I really could care less how fast it is on top.

 

[Stinnett21]

As a starting point put your info into the Mercury Prop Selector and see what it spits out.

 

[Stinnett21]

If you are not carrying as much weight as before and you are having to throttle back to not exceed operating range I would change to a 3 blade. I realize you are not interested in top end but efficiency is another factor.

 

[MBAKER]

I have run it through the prop selector before and end up anywhere from 15.5x18 black max, to 14.25x21. I am at 14.5x18 4 blade currently, have a 19 3 blade I can throw back on. One thing I remembered when we switched was the 4 blade did stay on plane 2-300 rpm slower which at times is nice. Interestingly I wonder if the 15.5 diamter 3 blade would be similar in blade area to the 4 blade at 14.5 considering the blade shape is slightly different from what I have seen. Possibly same blade area but one less blade to drag around.

We used to go out full of fuel, 4-5 adults plus kids, toys etc. Now I generally only carry 1/2 fuel, 3 adults and couple kids and half the toys. If we still loaded down what we have I'm sure would be fine. But am thinking 20 pitch 4 blade similar to what I have or 21 3 blade might be better for just cruising around.

 

[airshot]

If your engine is not capable of reaching its max wot rpm, then it is lugging down, using more fuel than necessary and putting excess load on the motor. Whether you run wot or not, having the proper pitch means your good thru all the rpm range, not just wot.