Engine occasionally revs when under load

[PiratePast40]

AQ130D w/ AQ280 outdrive. While headed back in last weekend, I noticed that the engine would all of a sudden rev up a few hundred RPM and then go back to our cruise RPM of about 4200. In the course of 10 minutes, it did this two or three times. The wind coming up the canyon at our backs was blowing pretty good and gave a bit of a chop, although I've been through that before and don't recall this happening. Gave it full throttle and it didn't seem to do the same thing for the minute or so I held it there. Going through other wakes at relatively high speeds didn't seem to repeat this. Was thinking that the prop might be breaking the surface of the water but didn't want to have the wife lean over the stern in the relatively rough water to look so can't really rule that out.

I'm thinking that a spun prop would show itself at all speeds under load so don't think that's it. Don't know the symptoms of a slipping cone clutch in the outdrive so not able to make an educated guess at that. Checked the oil in the outdrive and it's at the normal level, normal color, and no burnt smell.

Any ideas what it would be and what I could check to narrow it down?

I should add that the linkage is adjusted properly with the shift mechanism lever perfectly horizontal when out of gear and it engages fully when placed in gear.

 

[Don S]

Re: Engine occasionally revs when under load

I would go for another run when the water is calmer and try it again at that rpm. Wind and waves can do some funny things.

 

[aerobat]

Re: Engine occasionally revs when under load

While headed back in last weekend, I noticed that the engine would all of a sudden rev up a few hundred RPM and then go back to our cruise RPM of about 4200. In the course of 10 minutes, it did this two or three times.

i think the baby gives you a hint it is bored and wants to go ! c,mon , gun the engine and keep the lever hard on the table to give it what it deserves ! :facepalm:

seriously... i,m with dons opinion- maybe you prop ventilated form time to time on the choppy water , but you should feel it that it revs but the speed drops.

 

[PiratePast40]

Re: Engine occasionally revs when under load

I was hoping it was just coming out of the water a bit and that sounds reasonable since I've checked the obvious. Will take it out tomorrow and see how it goes. Didn't really notice a change in speed and since it was so choppy, was hard to read the numbers on the GPS. It's a little hard an the back to keep it wide open in the choppy water and the Admiral gets on me when we go over the bumps!

 

[PiratePast40]

Re: Engine occasionally revs when under load

Everything seems fine wasn't quite as rough today and didn't have any problems. Guess I'm a little sensitive to any noises I haven't heard before on this boat. :redface: