Spun prop hub or worse?

I'm dealing with a '77 Mercury 1150 / 115 HP outboard:

Last night while running at near top speed, without any warning or unusual noises the boat seemed to come out of gear and the RPM's skyrocketed. My hand was already on the throttle so I instantly yanked it out of gear thinking it had jumped out of gear or something. Once it was in Neutral I put it back into gear and I could hear the normal sound of when it engages, and the boat starts to idle forward, however when I eased down on the throttle the prop doesn't spin beyond the spinning that I had when it was idling, only the engine revs. I get the same thing when I put the motor into reverse.

I started limping the boat back toward the boat ramp and eventually I lost even the idle speed.....like the prop TOTALLY stopped spinning, however there was heavy boat traffic and the waves were rough so I killed the motor and we anchored and fished for a little bit till sundown when I could just run the electric trolling motor back to the ramp. So, after the boat sat for 90 minutes I start it up and put it into gear and once again I have good idle speed, and could even idle up SLIGHTLY and gain a little more boat speed as I went back to the ramp.

This morning I went out with the boat still on trailer / not running and put it into forward gear. I could spin the prop clockwise and I could hear a loud "CLICK CLICK CLICK" but it sounded like it was supposed to make that noise...very distinct, not some weird grinding click. When I put the gear into revers I have a SOLID lock on the prop as I try to spin it clockwise and counter clockwise.

Any thoughts? I'm thinking/hoping that the hub is slipping under the weight of the boat in the water, but it grabs enough in idle that it moves the boat before the RPM's are raised to the point that it just sort of free spins on the prop hub.

Any info or experience is greatly appreciated.

Re: Spun prop hub or worse?

It sure SOUNDS like a spun hub. If you have a propr shop in your area, not a real expensive fix. Between $40-$75 here in TX. If you remove the prop, it is usually apparent. (You will see damage from inside prop hub) While the prop is still mounted, the test is to put on some gloves and turn the prop against the lock, whether in forward or reverse. If you can turn the motor over, probably not the hub. If the hub slips before turning the motor over, bingo, there's your problem. Strongly encourage you to wear gloves, the prop is sharper than you think!

Re: Spun prop hub or worse?

I took the boat down to the river this morning.... having first scribbed a line along my prop, the prop hub, prop nut, and prop shaft. With the boat still on trailer I started it and put it into gear and slowly increased rpm to the point that the prop obviously wasn't turning what it should based on the RPM's the engine was producing. I pulled out of the water and sure enough nothing was lined up with the scribbed line I had made earlier. When I removed the prop I found pieces of rubber on the inside, as well as rubber along the prop shaft. I cleaned the shaft up, put on my spare prop and BAM....everything seems to be good as new.

So happy it wasn't a lower-unit issue. Thanks for the reply Jacket4life.

Thanks for the information above concerning a Spun Hub. I experienced the same issue on my 90 HP 2 Stroke Mercury outboard, but the one discussion I do not see is the over reving of the engine while in neutral. I ran through a very thick patch of weeds (but did not "HIT" anything specific), and as we proceeded through the weed patch, the engine lost power no matter how much I increased the throttle. I did not notice whether the water pump was functioning or not since it happened so fast. I shut the motor off and checked to see if there was anything restricting the prop and found weeds wrapped around the prop, which we cleared then tried again to get underway. When I started the engine it raced in neutral, I put it in gear and the revs slowed, but I had no power at that point. I tried again and experienced the same issue. My question is would this indicate a plugged water intake, causing the engine to rev in addition to the spun hub? I have seen other posts discussing a Poppet Valve and wondered if I might also have this problem where the water flow is restricted or the pump is plugged. Any information is helpful. Thanks in advance, Pkeeper52.

Yes you could have ingested crud into the cooling system and interfered with the cooling channels including the thermostat and poppet. However, I don't see a smoking gun for engine over revs. in N. Something else at work here. Work the prop problem but otherwise, the over temp alarm will tell you if you got your cooling system loaded up with vegetation. You can't get much through the water intake holes so my opinion is that something else is at play here.

HTH,
Mark

I would start out by putting up a new post by PKeeper52 and his problem. Different motor hp and possible year etc. you will get more response with a new heading on your specfic motor and issue.FYI there is no thermostat on a 77 Tower, another reason to start your own thread...Although it shows over 1500 views,so maybe I am wrong ,computers don't make mistakes do they?