RPM question

My son took out my old 1978 Cobia with 150 hp evinrude yesterday and was experiencing some high RPM at wide open. I have the same prop I have always had. He said hole shot was the same. Does this sound like a spun hub in prop or can something else cause these high rpms. He also said motor alarm beep beep beep while turning these rpms. I have a replacement 1984 powerhead with vro which oil side is disabled. I mix oil with gas. Any ideas what might be going on here. He only over reved it for few seconds and alarm went off when he dropped rpms in safe range. Any ideas whats up with this? Thanks

Mark the prop and hub , take it for a spin and see if the marks still line up.-------Was there anything like a plastic bag in the water that may have cut off cooling water to the pump ?

I really don't know about the cooling part,but I have beat in his head to keep an eye on water flow since he was a little tyke and he is 28 now. I was wondering if intermittent beep had something to do with the old VRO.I had a spun hub on an old 25hp evinrude once,but it would spin on take off. I will mark hub and take it out myself to see if it does it with me and if hub is moving inside prop,Thanks

Take the boat out yourself and see what the rpms are.

I"m going to take it out and check the hub, but he said it pushed nearly 7000 rpm before he slowed it down. when he slowed it down alarm stopped. Just wondering what the connection between alarm and rpm is, Thanks

Post a picture of the prop. Good chance if the hub is not slipping it is cavitating.

I'm at work now, but why would it cavitate all of sudden. Same prop that came on boat and never had much use. I brought boat from a work buddy . He put about 40 hrs on boat and keep it stored for almost 25 years. I figure hub should be the problem just based on year 1978,but still would like any idea why alarm sound while turing high rpms. I'm open for ideas on cavitation 14 1/2-19 prop and never cavaitated before.

Small pin holes in the leading edge will cause cavitation. What looks good to the boating public usually will not look good to an experienced Tech.

Anytime someone tells me of this type of problem, I look at the condition of the prop first.

Thanks for information on prop it could use some work on edge and several layers of paint are coming off near edge. will tend to that and see how it goes this weekend .