Yes they are a very simple motor.----Easy to diagnose and repair.-----The reed valve opens and slams shut up to 5000 times a minute.-----They rarely cause a problem.----I can not see , hear or feel your motor.-----Up to you to have a look at your reed valves.
If the lower unit is on your work bench and the flywheel does not turn.-----I would say the motor has to come apart.----Start with pulling a cylinder head.----I think your are in for an EXPENSIVE repair job.
Remove the drive ----Remove the motor.---Rebuild the transom.----Opportunity to make it stronger than when new.-----But inspect stringers under the floor as well before deciding on the transom makeover.
The cork float is still listed as the replacement today.----In my opinion that means it is very reliable.----OMC / BRP would not have that available if it was et up by ethanol in fuel. !!----I would not hesitate to install one.
The 7.5 model had a ----COMET ---decal on it.-----Intake ports on the side of the cylinder were smaller on the 7.5 comet than the lightning 9.8 engine block!
Hands on is the only way to check these things.----While boat is out of the water a compression test might be good to do as well.----Loud noises are not good.---Trouble shooting needs to be done.
Your lake might be 10 miles.----But when a motor leaves the factory they have no idea where it ends up.----The type of boat that it is going on !-----Or if the operator is 20 years or a 70 year old careful fisherman , operator
Was it stored with fuel in the carburetors.-----Having to use choke clearly indicates carburetors need attention !!----I am quite sure it is NOT a reed valve issue.----They rarely fail !
