Throttle is hard to move

I have a 1978 evinrude 15 hp and the throttle is really hard to twist. Any suggestions on what this could be or solutions on how to fix this problem thanks mike

Well, first off I am not a motor guy. But I had the same issue on an older 'rude that had not been used in a few years. The problem was dry/hardened lubricant. A really thorough cleaning and re-lubrication and it worked perfectly. Your result may vary, but it is easy to check and correct, if necessary.

Not to long ago, I read something on here that may help you. Someone was talking about how there motor would "throttle down" if they let go of the tiller (not a good idea when running fast but he was trying to troll just above idle). It was mentioned that some tillers have an adjustment for the tension. See if there is a knob on the end of your tiller that twists.

The Johnson 9.9/15 hp from that era have teeth in the tiller arm which control the throttle. If you are running the motor with with the tiller arm raised up, it is possible to slip the teeth so they no longer match up. This may cause the throttle twist part of the handle to be hard to turn. It can also cause the teeth to become worn out (as the grind against each other). This would be the first thing I would check because it can happen inadvertently. There is an article somewhere on the web which discusses this problem in further detail and it also said it was the one flaw with these motors.

I've got the same motor, learned alot about it from this web site
https://www.leeroysramblings.com/Outboard%20Motor%20Related/OMC%20outboard%20related%20articles.html

How about disassembling, cleaning, and re-lubricating all throttle parts. There is no magic bullet here, your engine is going on 35 years old. Time for some routine maintenance.