effect of additional weight

MBAKER

Petty Officer 1st Class
Joined
Jun 9, 2008
Messages
288
How much difference in prop selection would additional 850# make? Is it enought to justify 1 step down in pitch?


Went out to test new engine and 17P (aluminum) prop, but only had 2 adults and 1/4 tank of gas, Im guessing a more typical load would add somewhere around 800+ pounds passengers and fuel etc. I know currrent prop is too small, Im just trying to decide what prop to try next and dont have anything to base the weight effect on.

For reference its a Maxum 2100SR new 5.7 and 4 barrel package. Tested as stated above with 17P aluminum prop and it ran to 4800 (rev limiter) and still had more to go, . Based on how it 'felt' and how much throttle was left I think it would pull a 21P, (maybe 23 with light load) but would rather error on the small side just to keep everything freed up a little. Plus most of our activity involves watersports so top end is not important. I just dont know if 19 or 21 would be the next best try because of weight difference and how much effect the weight would have.
 

carey965

Petty Officer 2nd Class
Joined
Jul 25, 2010
Messages
176
Re: effect of additional weight

I know more weight will bring down your rpm. I had about 800 in my boat on the weekend and I was barely going above 4500 rpm. When it was just my son and I at less then 300 I was hitting the 4800 at wot. I'm running a 21p 4 blade prop. I would suggest that for yours. It will give you more of a hole shot but still give you good top end
 

MBAKER

Petty Officer 1st Class
Joined
Jun 9, 2008
Messages
288
Re: effect of additional weight

can i ask what motor you have and how big roughly of a boat?
 

carey965

Petty Officer 2nd Class
Joined
Jul 25, 2010
Messages
176
Re: effect of additional weight

i have a 18ft tahoe, with the 4.3 merc
 

MBAKER

Petty Officer 1st Class
Joined
Jun 9, 2008
Messages
288
Re: effect of additional weight

Ok, we have a 21' maxum w/ 350. I found a 19P 3 blade and 20P 4 blade I might try. I dont like to over prop them much at all, id rather have to pull them back on top end to keep from over revving. I feel its a lot easier on the valves...ask me how I know.
 
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