Changing prop this weekend...2005 Lowe FM165s w/4 stroke mercury 60

[NittanyDoug]

This weekend I'll be swapping out our prop for a Mercury Trophy Sport 13p. We got the boat with an aluminum 12p which didn't work for us. We couldn't run full throttle without the rev limiter alarm going on. We changed it out to the spare that came with the boat which was an aluminum 13p which was better but it's still over the recommended rpm of 6000 at 6200 rpm. So with the switch to stainless and an extra blade we should be in the recommended range of 5750 to 6000. That's based on stainless losing 1-200 tpms and the 4 blades loosing another 1-200. The 6200 trimmed out was running 34 on gps. The prop mercury prop calculator shows us at 41 mph with the new prop but I don't think we'll hit that. I just want to be in the range at wot and improve hole shot, decrease proposing and maintain at least 33 mph. Any thoughts if we will be successful ? I'll find out Sunday and report back but until them I'd love to hear thoughts.

 

[jestor68]

I'll bet $10 that you'll accomplish your stated goals.

 

[NittanyDoug]

We had an extra person on board yesterday, but we "tested" anyhow. The new prop topped out at 5600 rpm's and 31-32 per gps. It was a little choppy so it was touch to stay WOT and trimmed up nice. Overall the boat boat reacted nicely. Very little bow rise on throttle up. Maybe in a couple weeks we'll get back out and test it under our "usual" conditions. I don't know if the extra person factors in to the significant drop in the rpm's. I would have thought we'd have been higher in the 5,000's range.

 

[NittanyDoug]

double post..sorry.

 

[MikDee]

We had an extra person on board yesterday, but we "tested" anyhow. The new prop topped out at 5600 rpm's and 31-32 per gps. It was a little choppy so it was touch to stay WOT and trimmed up nice. Overall the boat boat reacted nicely. Very little bow rise on throttle up. Maybe in a couple weeks we'll get back out and test it under our "usual" conditions. I don't know if the extra person factors in to the significant drop in the rpm's. I would have thought we'd have been higher in the 5,000's range.

Not so with the 4 blade 13 pitch.SS, too many variables changed all at once. The same prop in a 12" pitch would have been better, but because of the forum issues I couldn't get to you sooner to reply .

 

[NittanyDoug]

I wanted to drop below the 6000 mark but not this far! I may see if my brother in law can take it out this week alone and give it a go to see how it compared to the 13p aluminum 3-blade we swapped out. I know we aren't going back to the 3 blade aluminum 12p tho. That thing ran way over 6000.

 

[steelespike]

Check out the tests on the Merc site. Something like "mercury outboards."
It appears that 90 % of boats like yours were running about 32 usually with a 13".
assuming the tach is accurate your old 13 was running at about 18% slip thats high,not necessarily wrong but high.
The ss prop is running at about 15% still a little high, about 13% is a little more typical.
Did the ss prop respond well to up trim? The Merc Spitfire 4 bld. seems to do really well.
I saw what I believe was an independent test on a 90 hp. straight change over 3 blade to 4 blade It shaved over a second off an already fast hole shot
and aded .2 to the top end.A typical 4 blade just plain loses top end and rpm.

 

[NittanyDoug]

It did seem to respond to the trim. I definitely noticed it but with the chop on the water and having the father-in-law along I didn't want to try pounding it out to see what I could get. It was less than ideal testing conditions. There was significantly less bow rise than the 12P. I may just bite the bullet and order the 12P Trophy Sport. I'm looking to have the prop that I don't have to swap out based on people/load granted we usually only fish 2 guys the majority of the time. I'll look again on Mercury's website. They seem to mainly focus on new/current models even though I don't think there was a big change in the motor we have from then till now.

 

[NittanyDoug]

We got out again this weekend. With 2 guys and a little better water conditions, we were spot on. Just under 6000 rpm's at WOT (probably 5900) and topping out a little over 35 by GPS. The boat responded well to trim and got on plane easily.