rattling noise coming from merc 120 - flywheel bolts?

[CamaroMan]

helped a friend get his 120 going, theres a rattling sounds coming from the bottom rear of the motor - it comes in around 1500 till 2500, nothing at idle or higher, sometimes it shows up for a second or 2 outside the rpm ranges. Ive read guys have had this with flywheel bolts coming loose -

Do i remove the fly wheel cover underneath the motor to access the bolts (like an auto trans)? Not even sure if I can get in there!

 

[GA_Boater]

Loose flywheel or coupler means the motor needs to come out. It isn't like torque convertor bolts in from the front and all flywheels bolt to the crank from the back.

Checked timing? You may be hearing pinging from advanced timing.

 

[Scott Danforth]

could also be flapper rattle

 

[Bt Doctur]

check the metal dust cover for a crack

 

[CamaroMan]

hi guys thanks for the replies, bummer if motor has to come out! yes familiar with auto and manual plates/fly wheels - wasnt sure if a boat coupler used a tc style or fly wheel :|

dust plate seems fine I had a look in there last week to see if any bolts were rattling.

Timing was good but light bust right after I set it, I have a new one so will determine true tdc and recheck..

fyi did replace ujoints, bearing, bellows - the works.. but noise is DEF coming from engine side, more near the back/lower area far as i can tell.

Whats the spec for setting valve lash, like a chevy? both valves closed, loosen till theres up and down movement on pushrod, once it seats - 3/4 turn.

At first i thought maybe it could be a tappet noise, but that shd be at idle too - anyway, ill recheck timing and valves and post back..

fyi it starts at the touch of the key and idles very well. put in a carb kit and fiddled with idle mix screws for highest vac at idle..

ive read about the "marbles in a can" but yikes if thats pinging its insane! never had that on any motor ive ever worked on!
maybe the dizzy springs are rusted and its advancing WAY to much, that wd explain the rattling only around 1500-2100 about..

 

[Bt Doctur]

Said check for a crack in the cover, not loose bolts

 

[hoowahfun]

fyi did replace ujoints, bearing, bellows - the works.. but noise is DEF coming from engine side, more near the back/lower area far as i can tell.

Did you do the alignment with the special tool when you did all this?

 

[CamaroMan]

hoowahfun - nope did not, but i did slide in the ujoint shaft separately thru bearing into motor - it came in and out very easily.. bt couldnt see any cracks - ill have a better look 2moro - thanks..