Motor knocking

[stunt_goldfish]

Just wondering if i could get an idea of what is going on with my motor. #It's an old mercury 50hp (late 70's i think). #Just bought the boat. #1st run was a dream. #Second run was good most of the day and then it started making a knocking noise that seemed to be coming from about 1/2 way up the leg. #This noise went away when held at certain revs but came back if revs were above or below that level. #(Could it just be the oil ratio????)

Hope it's not gunna be to costly cos my wife might take to me knackers!

[Owen]

Always hard to guess at a noise when you can't hear it, but if it comes and goes it could be a balance issue somewhere.
Did you smack your prop or anything?
I think your motor would be the same as mine, so should be oil injected?
Could also be a cracked piston
or timing too advanced
or.....

cheers,
Owen

[stunt_goldfish]

Even harder when you hear it knocking for the first time and still a few k's away from the ramp. Taking it to get looked at this week, so i'll post on here what they say. Bit worried. One mechanic says to run it until she blows up (that was without seeing it).

[stunt_goldfish]

Took the motor to mechanic today. It's knackered. Says it's pistons or con rod. Anybody have a 50 -70Hp they don't need anymore. Gonna be in strife with the missus.

[Rocketrody]

Mine all so has that knocking noise and its all so a mercury 50hp found out to day it was from the choke comeing on at certain revs and it was only the top carby Too. I tested the boat to day and now im Knocking FREEEEEE.

[stunt_goldfish]

Good work. Nah I've checked it out. Definetely knackered. At least my wife is coming around to the benefits of me getting a newer motor. Have to see how i go in the next couple of weeks. Just got back from fishing up at Quobba station so don't want to push my luck just yet.

[stunt_goldfish]

I've come across a 75hp Mercury, I think it's an 85 model. It's a brown band i think, not oil injected. Has anybody got any feedback for me about this type of motor. It's got power t/t. The dealer says it's been recently serviced by them and seals and bearings have been replaced. They're asking $1500 plus $300 to fit to my boat. Not sure if i'll be throwing good money after bad.

[snapattack]

Mate,

I'd be saving a few more bucks and buying a later model. A motor thats 20years old and a brown band mercury in my opinion would only be worth $500 bucks and that would only be for parts.

Try and find a 70hp mid 90's engine. Should be able to pick one up for between $3000 and $4000.

Good luck

Snap

[stunt_goldfish]

Thanks Snap.

There's a Yamaha 70HP? 92 model I can get for $2000 fitted. No power t/t though but it comes with a three month warranty. That sound better?

[foggy]

That sounds OK but check your PM's

[stunt_goldfish]

Thanks for taking the time Foggy,
have sent a couple of questions to them. Freight could be a killer as i live in WA. See what they come back with.