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Discussion Starter · #1 ·
I have a 92 18' Sea Ray with an outboard Mercury Black Max 135hp that currently has a 19p SS prop but I really think its the wrong prop for the boat. with 5 people, I was running about 4500-5000 rpms at about 24mph. when loaded the hole shot is horrible. At times I have been driving on plane (about 25mph) and hear the engine pitch sound just drop and the rpms also drop about 400rpms like the prop finally "caught" the water. Even alone I have never gave it WOT because the rpms are would go beyond 5500 rpms. I know I want to drop rpms with a larger pitched prop, but unsure if a 3,4 or 5 blade would be best. The boat is used for cruising and also wakeboarding. The only issue is with 2 people at about 3200rpms (20-22mph which is wakeboarding speeds) is where the power band ends, so anything below 3200 the motor will just drop down and the boat will fall out of plane, giving more throttle, it will just take off. right now I cant go beyond 25mph without having to many rpms with people and im just wasting gas spinning a prop that seems to be "slipping" I was looking at the merc high five 21p, not sure if i need more pitch or not as many blades, but i dont mind about losing a little top end, i just want a good holeshot with people and be more efficient.
 

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Not sure,
My 1st thought is, it sounds like your just cavitating, or the trim angle is set too high. Are you sure your shaft length is right for that boat, where's your cavitation plate in relation to the bottom of the hull.? I would think a good 3 blade prop of the correct diameter should be all you need for pulling.
You said you have a 19P now, but what's the Dia. and how many blades, ?
Not sure, but I don't think your going to ever see any great hole shots pulling a wake-boarder plus a boat load of people with 135 ponies though.
There's lots of OB guy's on here that will chime in soon, that will help you better than I can..
 

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Discussion Starter · #3 ·
I would have to measure everything, not sure off hand, its a 3 blade prop, not sure of the dia. would have to check. it could be cavitating some because the back corner of the cavitation plate had broken off, and never had a chance to repair it yet. I guess that should be fixed and see if things change, I do remember before it broke it was running about 3200rpm at about 20mph with 2 people (approx 350lbs)
 

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Is your prop ported ( little holes in the hub in front of the blades)? These help the engine spool up to speed until the hull gets moving, then it will "hook up" or catch in the water and take off in speed. Installing plugs in the ports could be what you need.
 
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