# Prop on one engine cavitating..



## Hard Core (Sep 24, 2008)

Howdy all...



I have got a problem that I can't figure out. In another message below I talked about spinning two props last summer on my port engine. I am running two 225 Yamaha 4 strokes. I went out yesterday to the Petronus rig. On the way out and on the way back in....the port engine prop would cavitate now and again. Once I pulled back on the throttle it would stop cavitating and catch up with the other engine. So...same engine spins two props last summer. First time out this year same engine wants to cavitate on regular but totally indifferent occasions. What am I missing??? Both engines were in full down position on the trim tilt. It was rough going out and got rougher during the day....so the going was slow. Starboard engine has never cavitated. This is a puzzler for me....all suggestions are welcomed...!!!!



Ronnie


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## DOUBLE "D" & LV (Oct 2, 2007)

When you say the engine spun two props last year, do you mean it spun the hubs? If you are talking about your engine raising rpm and loosing bite, then the prop is becoming ventilated by something. A few things can cause it. Usually, something is mounted closer than 9" away from the lower unit and causing turbulence to interfere with the prop, whether it be a through hull fitting or transducer. If the hub is being spun, the most likely cause would be the propeller is not mounted tight enough or the wrong thrust washer is on it. Forgot to add this. Engine mounting height will play a part in that also. If too high by a little, it will ventilate the prop on occassion depending on the situation.


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## Breeze Fabricators (Oct 2, 2007)

Also check the depth of cup in the side giving you the problem. Compare it to the other side and if it is less then bring it to the prop shop along with the other prop for them to match it to.


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## Hard Core (Sep 24, 2008)

> *DOUBLE "D" & LV (3/8/2009)*When you say the engine spun two props last year, do you mean it spun the hubs? If you are talking about your engine raising rpm and loosing bite, then the prop is becoming ventilated by something. A few things can cause it. Usually, something is mounted closer than 9" away from the lower unit and causing turbulence to interfere with the prop, whether it be a through hull fitting or transducer. If the hub is being spun, the most likely cause would be the propeller is not mounted tight enough or the wrong thrust washer is on it. Forgot to add this. Engine mounting height will play a part in that also. If too high by a little, it will ventilate the prop on occassion depending on the situation.




David...



I really appreciate the information you guys post on this forum. The next time I need engine work ya'll are going to get a call. Both times the prop spun the hub. Here is another bit of information. When in reverse for a period of time that same engine is not getting enough water. The alarm horn will come on. if I shift it into neutral the horn shuts off. Then I can shift it back into reverse holding my spot. Weird ain't it? I tell you what..I am going to look up your website right now and give you a call for the season tune up and to get this problem fixed. Will be talking to you today hopefully. 



Ronnie


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## recess (Oct 8, 2007)

I would check the hight of both engines. The pitch and dia. Are the props matched? The cup also. With the two spun props last yearsame side sounds to me that you have to much slip, if so that will cause an overheat condition in the props which leads to the hub to decentigrate. I would take them to accur prop or a good prop shop next to where you live. The good thing is that if ? you have to much slip it can be corrected and you will get better gas milage and a few more knots of speed at the same RPM.Also make sure that when you are running that both engines are sycronized. I had this problem and for me I changed the props to PTT SS and added 2 more inches of pitch and increased both speed and better MPG with 400 rpm's lower..


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