Setup Help please

[Miniton]

I am having some issues with a new "used" boat that I purchased. When under heavy acceleration and tight turns I am getting prop blowout. (or at least that's what I think it is.)

I have a 1994 Astro 20fsx fish and ski with a 1994 200hp Mercury Black Max. I get 64mph by Speedo,(no GPS) at 5300 rpm WOT with 2 people and 3/4 tank gas. Mercury Tempest SS prop # 48 825864 A45 23P

When I heavy accelerate from sitting still it starts to go a little then just high revs and spins without the boat going. I have to slowly throttle to get her up. Once running she runs great except in really hard turns when I try and accelerate. The motor is currently mounted on the second hole from the top so I have 1 more to lower it or 3 to raise it.

Is there anyone out there that can help me with this issue? I just have no holeshot what so ever.

Pics here: (http://s883.photobucket.com/albums/ac31/miniton70/)

Thanks in advance to all you experts,
Mini:confused:

[Charger200]

It is a cavitation issue. I dont think that is the right prop for your boat and i would try trading for a same pitch or one higher trophy. It doesnt seem like the motor is mounted too high but how is your trim upon take off and hard turns. if you have too much trim any prop CAN cavitate and loose grip. Try using about 3/4 throttle on take off and when it starts loosing grip peddle it a bit(let off) and get back in as it re gains. My 26p chopper is a pig sometimes if i get too heavy on the throttle taking off.
Hope this help Jay


Cavitation: The formation of “voids” or air inside the water stream, caused by low pressure near a surface. Encountered when the water separates from the propeller. Also called “ventilation”; causes propeller burn, and can lead to “blow-out”.

[Charger200]

Oh yeah Welcome aboard:thumbsup::cheers: theres alot of knowledge here no question is stupid. as long as you remember to use the search button befor asking a pretty general question. But if its a very specific question fire away

Jay

[Wizard]

The Tempest was made for bassboats and carrying weight so I think the prop is a good choice but there may be a problem with it. I see it's an older prop and does not have the PVS plugs but some vent holes in it. Are they square holes? Your engine is pretty low. Looks to me like about 5" below the pad. You should be able to run closer to 3" for more rpms and better performance.

I assume your starting off with full negative trim. Here's what I would try.

1. Fill the vent holes with Clear RTV and let it harden overnight then run it. This will test if vent holes are causing the ventilation. If it goes away then leave it. If not just pull out the RTV.

2. Borrow another prop to try. It could be anything in 21-26 pitch just to try and eliminate whether your current prop is damaged. It looks a bit small for a Tempest. Sometimes when damaged cheap propshops just grind off the damaged part and make the blades equal. This competely changes the progression and will kill performance.

3. Try raising the engine up. You can do this without a hoist by using the trailer and a couple of pairs of hands. Just lower the skeg onto a 4x4 loosen the bolts. Have two friends hold the engine steady then raise the trailer tounge by cranking the wheel. It's pretty simple.

My bet is you have a damaged prop. Another tempest, trophy, powertech, fury or other bassboat type prop should work well. :cheers:

[200VEGAS]

your rpm should be at least 300rpm higher and i agree with maybe a trophy or just anything ss to try to get a baseline. i think that prop doesnt blow out very easy if it is stock. do you trim out a lot on launch or trim in at take off and some for turns and eventually i would definatly look at a plate 8 "or so looking at it, but i am guessing cause it looks heavy.