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Propeller question

R

rupaul

New member
mercury 90 2 stroke on my astr

mercury 90 2 stroke on my astro 15 ft. laser II prop with a 22 pitch. with 1 person 5150 rpm with 2 people 5000 and with 3 people 4900 rpm. 1st. question what kind of increase would i get from gaining 300-400 rpm's. it does 47mph at 5150. 2nd. question should i replace the prop or is it ok to repitch it since it is stainless. thanks for any advice in advance
 
Just me but I'd buy anothe

Just me but I'd buy another prop. If you have a good dealer in the area they will some times let you try a few different props until you find the one that works the best.
Of course they expect that you will buy one when you do find the one you like. So don't jerk them around by going to another place because it is cheaper or by taking the one you have and re-pitching it to the size that worked. If you do the next time someone needs a favor the dealer may tell them to go pound sand and it could be you.

Also expect to buy any prop you damage if it is a new prop. Even a chip in the paint. Fair is fair. The guy trusted you to return the part undamaged. He can't sell a prop with damage of any kind as new.
Good luck.
 
"Robert, I think you are pret

"Robert, I think you are pretty near optimum for that setup. Are you sure the speed and RPM numbers are accurate? if you are using GPS for the speed, then thats OK. Now find a RPM calculator and punch in your speed, gear ratio and 10 - 12% for slip. If the RPM is near what you are seeing, then your Tach is calibrated.

Clearly a 21" pitch prop would be good to try, but may or may not boost speed. Is your trim near max?"
 
i just bought this boat a few

i just bought this boat a few weeks ago and it is my first boat so i don't really know what i am doing. the trim is as far up as it will go i guess. i can full throttle the boat then start raising the trim up. when i do the speed and rpm's go up accordingly. when at full throttle i can start to trim up the motor but it will only go up so far before the electric motor just can't raise it any further. if i had to guess i would say it is about a 18-20 degree angle. is this right or not? thanks
 
"Robert, The trim is designed

"Robert, The trim is designed to only go up to a certain point, so your setup sounds OK. 47MPH is a pretty good top speed for that rig. Your RPMs are low, but who knows if the Tach is working correctly. If you have a good, quick start from idle, with an average load of gear and people, you may be near optimum."
 
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