"weird" cavatation problem?

[n20michael]

Hey Guys!

I was out yesterday and easing my boat on plane the boat started to cavitate, normally when this happens I back off a bit, get back on the throttle a little harder and the boat jumps right up on plane, this time after 4 or 5 times it wouldnt stop cavatating, I had the trim on the throttle all the way down. Finally I pushed the trim button the dash "down" and got back on the throttle and it planed out no problem?
I pulled the boat today and the trim seems to work fine on both the throttle and dash, any thoughts?

[sprink58]

Sounds like you might have torn the hub loose in the prop....take a look at it ...or pull it and have a prop shop take a look at it. If it has to be re-hubbed it's not that big of a deal. This is not un-common with high powered engines on heavy boats.

[n20michael]

I looked at the prop quickly, it "looked" ok and turned freely, how would I tell if its torn the hub loose? I thought it was weird that it seemed fine when I used the trim switch on the dash, but, that could be a co incidence

The trim pump doesnt "stop" either when I put the outdrive down. It stops when I put the drive up, but, when I put it down the pump keeps running, I guess that could just be a limit switch?

Any thoughts? Input is appreciated (-:

Michael

[sprink58]

Prop shops can tell quickly. They lock it down on a splined shaft and turn the prop on the hub with a tool they have. If it's loose, the re-hub it.

[dcb]

You could have had some trash hung up on the outdrive, I had a plastic bag hang up on one of mine and the prop cavitated the same way.

[US1 Fountain]

The trim pump doesnt "stop" either when I put the outdrive down. It stops when I put the drive up, but, when I put it down the pump keeps running, I guess that could just be a limit switch?

Any thoughts? Input is appreciated (-:

Michael

That's normal. There is no limit switch for the down position, just up. If you were to hold your trailer button, the pump would continue to run also.

[88Fount33]

I do that if I try to increase RPM too fast when trimmed in with the tabs down, specially in 90 to 95 degree water. It is worse in the location where the the slow speed zone ends and you can come on plane. If a big cruiser or three or four boats in front of me take off and aerate the water good, it is like I am in neutral. My procedure works 90 percent of the time, but there are times when I am in that kind of water and/or my passenger load/fuel load is just right that it will ventilate the props just like spinning tires, all show and no go.

[Too Stroked]

You could have had some trash hung up on the outdrive, I had a plastic bag hang up on one of mine and the prop cavitated the same way.

I'm going to second that opinion - with a little qualification. We get trouble calls from out on the lake all the time at this time of year for the same symptoms. Nine times out of ten, it's weeds wrapped around the gear case.

I got a call Sunday from one of our rental boats with the same symptoms. I told him to put it in reverse and gun it briefly. He claimed to have done it. Then I told him to trim the outboard up and check it. He claimed to have done it. So, I run down the lake in the service boat and pull up beside him. I have him trim the motor up and - guess what? - weeds. One pump in reverse and he was off and running. What a waste of time.

[n20michael]

You guys have forgotten more about this stuff than I will ever know (-:

It IS actually pretty weedy near my dock, the fall is near and water level has dropped. I did shift into reverse (at idle) and back into forward, but, I am beginning to think it could have been weeds and when I turned 180 degrees to head back to the dock the weeds fell off.

If it happens again I will trim
Up the outdrive and check for weeds, if its clear I will look into the hub issue.

Thanks guys! I sure appreciate all the help

Michael