Help please

[tbouget]

I have a 2000 model sprint fish and ski with a 2000 model 200hp Johnson motor wit a 21 pitch 3 blade prop. When making turns it seems to blow out and cavitate. I have been told this is what you should use by some people. Some have told me to switch to 21 pitch 4 blade. Some have said us 23 or 24 pitch. Anyone have any experience with this?

 

[Sea Rider]

Welcome to Iboats,

It's not a prop nor a pitch issue. It's a badly height seated OB on transom, sits too high, need to lower it down till aeration stops when at tight close turns on flat calm, no wind water cond. Must have deck weight well balanced, be well trimmed to achieve combo running parallel to water level when on plane. Post a pic shot sideways showing medium to lower leg area..

If wanting to get the Max HP out of that 200, once OB is correctly height seated on transom, go for a wot spin as usually loaded and check max wot revs achieved, latter can dial a prop that revs around full wot revs range. That's were the fun really starts..

Happy Boating

 

[Texasmark]

You can cause that (Ventilation) by having trim too far out and/or turning too hard in the turn, especially in rough water, in either case going to fast. Cupping is there to help in preventing blowout. Now how do you suppose I know that.....Grin. Are you running a high performance SS prop or an OEM original aluminum? If the latter, you can do a lot to correct that problem with the right SS prop. I don't see how increasing pitch would help you. I think it would hinder you because for a given rpm, the higher pitch would be grabbing for more water and with your air problem already, it would just opt for air that much more. Besides, more pitch could screw up your other performance parameters, like where is your current WOT rpm with your standard load in a straightaway, how is your hole shot, how does your boat handle "just on" plane type of things. A 4th blade of the same or one inch lower pitch may help, but needs to be cupped also.

 

[jimmbo]

I have a 2000 model sprint fish and ski with a 2000 model 200hp Johnson motor wit a 21 pitch 3 blade prop.

What is your current prop, Aluminium, Stainless steel? As mentioned earlier, how is the motor mounted heightwise in relation to the bottom of the boat? If it mounted so the Anti-ventilation plate is higher than the hull bottom you have a couple of options; 1) lower the engine till the prop is gripping the water solidly, 2) install a prop with more rake and cup, ie; RAKER, Stiletto, Laser, Enertia, Vengence.

 

[tbouget]

Thanks guys will post pic tomorrow. I am running stainless steel prop. Happened again today pulling a tube. I have to give it more gas during turns just to keep the speed. Frustrating! !

 

[Texasmark]

Thanks guys will post pic tomorrow. I am running stainless steel prop. Happened again today pulling a tube. I have to give it more gas during turns just to keep the speed. Frustrating! !

Under load you need to get more water over the AV plate....pulling a tube is a load. So don't expect "dazzling performance" options to cure your problem. As the other guys have said, if your main attraction is tubing or skiing, or joy riding a boat full of folks and all, then engine height reduction is certainly in order....besides the prop concerns!

 

[tbouget]

You guys were right the motor does sit up to high. I guess a jack plate is my option?

 

[H20Rat]

Pics will greatly help! Jack plates are usually a cure for a boat that needs the engine up higher for optimum performance. Can your engine be mounted lower instead?

 

[jimmbo]

We are waiting for the Pictures. Tap tap tap(that's my foot)

 

[tbouget]

Sorry boat is still in the water lol. On vacation so so still fishing. But I will as soon as I take it out to filler up.