Would a spun prop hub cause over speed alarm?

[JwD57]

I was on a fishing trip and my yamaha 90hp 2 stroke seemed to be running fine. When i got to a certain speed it would choke down and go into "protect mode" (on two out of three cylinders i believe) and an alarm was on. After letting it set for a minute we restarted it with no alarm. When i wasnt running it wide open it would run great. This happened again on a different trip. After doing this 3-4 times, we had to idle back to the ramp as if the hub had completely slipped. Would my spun hub have caused this alarm and also do they gradually slip or would it have spun all at once? Thnx

 

[Grub54891]

Re: Would a spun prop hub cause over speed alarm?

What you can do is put it in gear,motor turned off,and grab the prop and see if it slips on the hub.mark the prop and hub with a sharpie and see if it moved on the hub.Sometimes it takes more torque than doing it by hand. You can mark it and take it for a ride and check it when you load up,betcha it slipped.they can be rebuilt if you like.
Grub

 

[mpsyamaha]

Re: Would a spun prop hub cause over speed alarm?

Doesnt really sound like spun hub to me... the most load is being put on that hub when you are pushing a bow wave trying to get on plane. if the boat was able to get up and go, but only had an alarm once you near WOT im guessing you were overheating. A spun hub happens all at once in my experience, once its spun... its spun. Every one that I have seen was still able to bring the boat back in, but not able to get on plane (or go much above idle speed). I have heard stories of them slipping bad enough to not move the boat at all.

What rpm was the alarm happening at? It will hit a rev limiter at a certain point, but that shouldnt sound any alarms on that motor. What you described sounds more like the motor was going into rpm reduction, due to either temp or oil level.

 

[etracer68]

Re: Would a spun prop hub cause over speed alarm?

I would agree^^^^, What he said,^^^^

 

[Scott Danforth]

Re: Would a spun prop hub cause over speed alarm?

If you know your hub is spun, then yes, it will cause an over-speed because the connection between the hub and prop has been compromised.

If you are guessing that it may be a spun hub, take a sharpie marker on the hub and prop, go for a ride. if you come back and the lines have moved, then you have a spun prop. if the lines have not moved, then your prop is fine.

If your prop is good, make sure your not overheating as suggested. when was the last time the impeller was changed?

 

[Texasmark]

Re: Would a spun prop hub cause over speed alarm?

I hit an object once and it caused the hub to break loose and a sharp decrease in speed and increase in rpms. I throttled back to N and Immediately back to F with full power and went on my way.

Another time with a different prop it would slip, catch, etc. till it finally would not do the hole shot. Agree the hole shot is the max stress.

SWAG is that they are all different. Just depends on what's going on between the rubber and the metal in your particular application.

The mark and run method is a sure nuff check. If the marks have moved it is slipping. And as said, you may need the power of the engine running to test it correctly; as said it depends on that particular relationship.


THT,
Mark