I have an '84 Merc 115 that started acting up on me this past weekend. I was running on plane and trimmed when the prop all of a sudden seemed to just lose its bite. Boat came off plane and the engine reved like someone had just stuck it in neutral. I quickly backed off the throttle and checked things out. As far as I could tell I didn't hit anything in the water and everything with the prop and lower unit looked normal. I trimmed the motor back down and got back on plane with no problem but I noticed that anytime I got above 4000 rpms, the prop would lose bite, boat come off plane, and the engine rev up. As long as I would stay under about 4000 rpms the motor would run fine, get up on plane with no problem and trim out with no problem. When I got home I took the prop off and didn't notice anything out of the ordinary. Wondering if I spun the hub in the prop or does this sound like something in the lower unit? Haven't heard of a spun hub holding enough to get the boat up on plane. Help please.

All the props I have known that have been spun you can't get out of the hole. It may be something else. Get it checked out.

I spun my hub and it would still
hit about 3500 rpms before it slipped.
I started running back to the dock
and after a couple of miles it quit
all together.

Thanks guys for the replies. Been doing some research and from what I've found the symptoms are consistent with a spun hub, just maybe not totally gone. I'm going to mark the hub and prop, then run it and see if the marks still line up.

this was exactly what happened to me. was running along and then it was like the motor slipped out of gear. got back on plane and ran about 4k rpm for a couple seconds, then it happened again. after that, it would just about get up, then slip.

i wish i could find a solid hub prop!

also make sure you are trimmed down. was at the lake one day and i couldn't get on plane. i figured i had spun it, until i noticed the plate was all the way up!

Take the prop off and inspect the rubber hub from the back side. If it's spun, you will see where rubber has melted due to frictional heat. Just take it to a prop shop and get a new hub pressed in.

KingBingo, you don't want a solid hub prop. Just think anytime you hit something no matter how small it would do damage to your gears, shaft or your crank. Bad choice. Unless of course you are running where there is nothing to hit, then you just have to put up with the extra little vibration a solid hub produces.---Smitty

Well, I did my test run yesterday and sure enough the hub is slipping. I marked hub and prop, then got the boat up to speed so it would slip. When I pulled the boat out of the water, the marks were 180 degrees out. Taking the prop over to Nettles at lunch today. Thanks for all the help.

i generally run in 30'-100' when fishing fresh water.

also, when i was kid in louisiana, you would be running along and get into a mud patch, sand bar or oyster reef. we would just apply power and go on through.

i wonder if a prop with a "hub" would stand up to this? sure would suck to spin it on top of a mud flat 20 miles from the ramp in the middle of nowhere!

should not cost more than 40 bucks to have a new hub installed at a prop shop. Same thing happened to me about 10 miles from the boat ramp at Lewisville in rough water. Luckily I had another prop that i installed after idling to the shore.