Good engine cleaning

I purchased a '73 20 hp mercury with electric start that runs great but is really grimy under the cowling. What are some good "do and don't " tips for a good cleaning? Areas to avoid with degreaser and power washer?
Thanks ....newby here. Just want to give a good cleaning without inflicting damage

That outboard is pretty bullet proof. I have a similar 4.5 hp that was an underwater recovery. After draining all the water out and flushing it through with mixed gas, ( you wouldn't have to do this step of course), I sprayed it with Gunk engine degreaser, then hosed it off with hot water. Then dried it first with compressed air, then out in the sun......or a hair dryer. I just made sure the carb was tightly plugged off with a rag. Afterwards I started it and warmed it up. Can you believe I never even had to remove the flywheel to clean the spark components? That was almost 15 years ago, and it has good spark to this day.

Smith0131 said:

I purchased a '73 20 hp mercury with electric start that runs great but is really grimy under the cowling. What are some good "do and don't " tips for a good cleaning? Areas to avoid with degreaser and power washer?
Thanks ....newby here. Just want to give a good cleaning without inflicting damage

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Leave it be. The wires on those mercs are good for having the insulation degrade. Anything you do could make the insulation fall off.

Well that depends on what they look like, Mr.Scott. If oil and fuel mix is left throughout the motor, you will destroy more than just the wires. The owner should clean it and find the source of the leak. Without a cleaning, that might be very hard to do and furthermore, if ethanol is present in the cruddy mix, there will be even faster deterioration. The main cause of the wire insulation breaking down is age and heat, add the crud to that and you have even faster breakdown. Been at this a long time, brother. Rebuilt my first 2 1/2 Johnson at 10 years old, been at this steady for 52 years. If I don't know what I'm talking about, I will ask someone with more experience.......and an open mind......first.

It is a well known fact that Mercury used a low quality wire in the 70s. Maybe in your 52 yrs you would have run across this, I have many many times. Clean it at your own risk. No mention of a leak in the OPs post where did that come.