Cavitation Plate Height

[czkidd]

I have a Pursuit 2150 CC that was repowered with a 2003 Yamaha 200 HP Saltwater Series 2. The old Engine was a 200 HP Yamaha Saltwater Series 1. After running the boat the performance seems to be way off and very sloppy. I cannot get the bow to lift. As soon as I pitch out the engine the propeller blows out and I lose bite. This prop was on the old engine and I did not have this problem before. Both engines are 25" shaft. I did notice that the cavitation plate is about 2-3" above the bottom of the boat. Are the bubbles that are being trapped under the hull when I'm under way running under the cavitation plate and getting sucked into the water stream that feeds the propeller? Is the cavitation plate to high? I'm running a 3 blade 13.75x17 wheel uncupped. I also notice that I cannot get the same top speed as I used too. Before the repower, 41.5mph at wot running 5500 rpm. Now 38.5mph at wot running 5200 rpm. All help and experience will help. Thank you. Czkidd

 

[Dhadley]

Re: Cavitation Plate Height

What prop did you run before? The one you have now seems like a very low tech deal with a small diameter and no cup. Is it aluminum or stainless steel?<br /><br />This motor has HPDI, correct? How much time is on it?<br /><br />Good luck!

 

[thehermit]

Re: Cavitation Plate Height

kidd,<br /><br />I believe the rule of thumb is that the cavitation plate needs to be in line with the bottom of the boat (on same plane - use straight edge). If the boat is a deep V it could be above the absolute bottom but on plane should be @ the water line (not above or below). If both motors are 25" do the transom brackets somehow differ (raising your new one in te same set of mount holes)?<br /><br />TH<br />______________________________<br /><br />fish on!

 

[boaterntexas]

Re: Cavitation Plate Height

I'm ahving the same problem on my 17.5" fiberglass bass boat runnign at 115 hp merc. my cav plate is about 2" from teh bottom of the boat also. I had a hydrofoil stabalizer on mine, when I removed it, it help top end and plane out at little bit. but I still suspect that the cav plate is just to high, hole shot is horrible still.<br /><br /> thomas

 

[FredM]

Re: Cavitation Plate Height

I have read and been told that the anti-ventilation plate should be about 1" (but no more) below the keel line.

 

[KNOTTY THOTS]

Re: Cavitation Plate Height

I have a 2001 Yahmha 150 and the manual shows the anti cavitation plate 5" above the bottom of the boat. I raised mine just a little higher to get a little more speed but do get some blow out when taking off hard. I don't think the 17 pitch prop is a problem too as i have the same prop and my rev's are too high, and i need to get a 21 pitch prop thought i would loose some hole shot.

 

[czkidd]

Re: Cavitation Plate Height

Thanks for the info regarding the Cavitation problems I'm having. The propeller is the original one that was mounted to the old motor. The engine is mounted at its lowest setting.(top hole of the mounting bracket). I called Pursuit and was told that the 2150 CC ran Neutral or even slightly bow down. I was also told by a Yamaha dealer to measure the shaft length to verify that I did receive a 25" model. Mistakes can happen. I will also switch to a cupped propeller. I'll try a 14.5x17 and see if the cavitation stops. Last resort is to install a transom bracket. Thanks again for the info. Little late on replying. Working down in Key West.