77 fiberform sterndrive by mercruser

[Rob the new boat mechanic]

While out on the river the other day we was pulling another boat and the forward propulsion quit it runs Forward at idle speed but you give it gas and it does not accelerate it actually seems to slow it down the reverse works. Almost as like on car clutch is ingaged . there is a vibration or clunking sound that goes on and quits every so often . I'm new to working on boat motors Etc so I'm wondering what this could be the cause of I've been told it would be the gearbox but that's why I subscribed here and hoping you guys can help me figure out what to do from here please and thank you

 

[Rob the new boat mechanic]

If it matters the engine is a 302 v8

 

[Bondo]

Ayuh,...... Welcome Aboard,..... To diagnose yer problem, drain the outdrive, 'n inspect the oil for metal,......

 

[Scott Danforth]

could be upper gears in the drive are gone
could be low on oil and whole drive is gone
could be coupling is gone
could be a few things, even a prop hub

start by oil sample like Bondo stated, if you have metal bits then look at the upper gears.
if thats good, then pull the drive and inspect the coupler. (you probably didnt do that bit of maintenance when you bought the boat anyway.)

 

[Rob the new boat mechanic]

Thank you i will start on that today

 

[Sterling Marine]

Check prop for a spun hub. Easy stuff first