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Prop hub or coupler

crossram

New member
I took my 1977 marquis with an

I took my 1977 marquis with an mercruiser 898 drive out for the first time this year and when I was up on plane about 3800 rpm the engine free reved .I droped it back to neutral and hit the gas it took off fine ran good for a few then it happened again.it never cam back to where i could hit the throttle. you can here it ingage and will move on idle but when get on the throttle it just free revs.any thoughts before I pull the engine?
 
Likely the coupler.
You will


Likely the coupler.
You will need to pull the drive and R&R the engine to get the bellhousing off and replace the coupler.
Maybe an idea to drain a little drive oil off the bottom and check for metal just to make sure it's not that.
Rod
 
nothing in the drive oil.out o

nothing in the drive oil.out of the water i can put it in forward and it locks in and cant turn by hand . How much force would it take to spin the prop on the hub {bonded hub}?
 
This sounds like a prop hub pr

This sounds like a prop hub problem. Engine couplers don't "engage" again like a slipping clutch on a car. Couplers do. Take the replacable hub out and look for hairline cracks.
 
"pull, and check the prop. som

"pull, and check the prop. sometimes you can see evidence at forward end. you could also put a punch mark on prop, and washer. run, and see if they move in relation to each other. unlikely you could spin the prop by hand, unless you are a lot stronger than most.(and a couple of hundred horses)"
 
"Well then I would have to tha

"Well then I would have to thank it is the hub. I can spin the prop with a good amount of force.thanks for eveyones input . Ill get another prop and let you know,and Rod good spread sheet on props."
 
"Yup!! I had the same problem

"Yup!! I had the same problem (another prop or coupler post down a ways) The whole ass end of the boat would vibrate as the prop grabbed and slipped at 2500 rpm I could even stand on the prop, and the engine would turn, but standing on a prop does not come close to the torque thats on it at 3000 rpm.. I ran a Q-tip around the entrance to the engine coupler figuring if there was any wear, the by products would show up in the grease but nope, nothing but grease so I was pretty sure it was going to be the prop.. I put on another prop, launched the boat on Sunday, and drove it 20 miles to the marina .. Not a hint of a slip or vibration.. Yup!! It was the prop..A LOT cheaper than replacing the coupler.. Stick on another prop and take it for a spin..."
 
Put a new prop on last night a

Put a new prop on last night and took it out ran great. Droped down from a 15 x 18 to a 15 x 17 gets out of the hole better. now I need to tighten up the stering {a little sloppy.}and tweek the carb a little. thanks guys.
 
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