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Author Topic:   Another prop application. Suggestions?

JohnJ80 posted 06-13-2003 03:57 PM ET (US)
I have a Dauntless 15. I just repowered it and I am getting it pretty well set and tuned in (vertical placement, fins etc..). The motor is a 2003 FICHT 75HP from evinrude and it works pretty well on the boat. Motor is mounted one hole up from all the way down (AV plate ~1/2" above bottom of boat). I still get a v shaped spray off the lower unit when trimmed to 15-20% up. I'm going to raise the motor one hole this weekend to see what that does.
With all this done, the boat rides and handles pretty much as it did with the old motor - a 1994 70HP Johnson 2 stroke (much lighter motor).
Because of the waters that I boat in - it can be pretty rough due to boat wakes (3' boat wakes) and wind (2' waves)- I would like to have more trim range. Right now I trim to about 25% up for most running around. Beyond that, the boat acts bow light and can start to porpoise. (I think that this would help the porpoising above 25% trim too). In dead calm at high speed I get to 40% (WOT). Speed seems pretty good - in the low 40's for the most part.
The prop that is on there is a 13.75x15 aluminum. I have been looking at Sal's recommendations of Stiletto and they have a 13.25x15 that would fit. They tell me that this should give me about 50% more trim range (approx 40% or so on the gauge).
The WOT rpm range recommended for the motor is 4750-5250. Most of the time I am in the range of 4900 (loaded) to 5100 unloaded and max trim up. With a moderate load (two passengers ~ 300lbs of passengers) she will run 5000 rpm at WOT and 25% trim - nominal.
I'm thinking I need a prop with some good cupping. What happens if the prop size drops from 13.75 to 13.25?
Other recommendations for prop? Which would you choose and why? We mostly fish, run around and pull the kids occasionally on a tube.
Other questions: I have seen props advertising 'stern lift' and 'bow lift' is this the same thing (advertising) or are they different? Does this provide a significant difference is that just hype?
Comments?
j.

Bigshot posted 06-16-2003 10:44 AM ET (US)
Try jacking it up before you mess with props. Your range is pretty good. The porpoising is probably because that engine weighs 120lbs more than your old 70...those fisht are heavy, especially for a 75 which is the same as the 115. You would benefit from say a 13.25x15 Stainless.

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Author	Topic: Another prop application. Suggestions?
JohnJ80	posted 06-13-2003 03:57 PM ET (US) I have a Dauntless 15. I just repowered it and I am getting it pretty well set and tuned in (vertical placement, fins etc..). The motor is a 2003 FICHT 75HP from evinrude and it works pretty well on the boat. Motor is mounted one hole up from all the way down (AV plate ~1/2" above bottom of boat). I still get a v shaped spray off the lower unit when trimmed to 15-20% up. I'm going to raise the motor one hole this weekend to see what that does. With all this done, the boat rides and handles pretty much as it did with the old motor - a 1994 70HP Johnson 2 stroke (much lighter motor). Because of the waters that I boat in - it can be pretty rough due to boat wakes (3' boat wakes) and wind (2' waves)- I would like to have more trim range. Right now I trim to about 25% up for most running around. Beyond that, the boat acts bow light and can start to porpoise. (I think that this would help the porpoising above 25% trim too). In dead calm at high speed I get to 40% (WOT). Speed seems pretty good - in the low 40's for the most part. The prop that is on there is a 13.75x15 aluminum. I have been looking at Sal's recommendations of Stiletto and they have a 13.25x15 that would fit. They tell me that this should give me about 50% more trim range (approx 40% or so on the gauge). The WOT rpm range recommended for the motor is 4750-5250. Most of the time I am in the range of 4900 (loaded) to 5100 unloaded and max trim up. With a moderate load (two passengers ~ 300lbs of passengers) she will run 5000 rpm at WOT and 25% trim - nominal. I'm thinking I need a prop with some good cupping. What happens if the prop size drops from 13.75 to 13.25? Other recommendations for prop? Which would you choose and why? We mostly fish, run around and pull the kids occasionally on a tube. Other questions: I have seen props advertising 'stern lift' and 'bow lift' is this the same thing (advertising) or are they different? Does this provide a significant difference is that just hype? Comments? j.
Bigshot	posted 06-16-2003 10:44 AM ET (US) Try jacking it up before you mess with props. Your range is pretty good. The porpoising is probably because that engine weighs 120lbs more than your old 70...those fisht are heavy, especially for a 75 which is the same as the 115. You would benefit from say a 13.25x15 Stainless.