Over revving

[captncrunch]

I was out over the 4th holiday boat was running fine. After fireworks we (along with three or four hundred boats started back in. The water way was very crowded and many boats were trying to get through the same channel.

My boat, a 1987 24' Sanpan w/an 89, 88hp Evinrude, brand new SS 13 1/4 x 17 was running about 23-24 mph on the way in. with quite a bit of traffic passing us and some being passed I noticed my engine revved and seemed to be loosing power at the same time. Nothing struck, matter of a fact I was in 60+ feet of water. had to slow engine to stop. Then shift back into gear, engine would not get above 15-16 mph before it would do it again. Third time shifted into gear and crept to the nearest boat launch. Pin and nut still on prop, boat pissing well, no alarms. after half hour inspection cranked up returning the rest of the way home. Every mile or two I would ease up my speed till (20 minutes or so later and prob. 15 mile later) I was back running mid 20 mphs.

Any suggestions or ideas??

 

[bktheking]

Re: Over revving

Was the motor tilted all the way down, could have been ventilation causing it especially with a lot of traffic in the water.

 

[captncrunch]

Re: Over revving

ventilation???

 

[bktheking]

Re: Over revving

Ventilation occurs when surface air or exhaust gases are drawn into the propeller blades. The load on the propeller is reduced by the mixing of air or exhaust into the water steam causing over revving.

 

[Daviet]

Re: Over revving

Might not hurt to check and see if the prop hub spun.

 

[captncrunch]

Re: Over revving

I do not believe the prop is spun. I was afraid of that at first. When I finally got the boat home I came to a complete stop on very smooth water and a couple of times gave it full throttle both forward and reverse. No spin again.

I was concerned it might have been an issue with the shaft coming out of the foot the prop sits on.