Id say if they look good and no miss fires run them, all depends on hours of operation a year, 126 hours total ?

I was told to change them 100 hours max on N/A motors and 60 hours on Blower motors.

I Think those coils would fire the plug even with the tang blown off. They sure run better with fresh sparkplugs though

every marine engine is different even if its the same engine across the board and the different environments they live in ... This question can not be answered about when to change sparks plugs especially without looking at them nor knowing many UNKNOWNS . I would change them as plugs are cheap anyways.

to further expand on changing spark plugs

One would have to ask many questions or know -- has the engine been over heated ? does it run at a steady correct temp at all times or does it run cold or does it run hotter than spec - How about moisture in the air or even experienced water reversion ?

Is the gas fresh all the times because old gas does not combust like fresh quality gas - any additives added to your gas, that changes the specific gravity of ones fuel in return effects rich / lean conditions -

how old is ignition components and how about the quality of them - how do you lay up your boat and engines ? How good is your piston ring seal and compression numbers.. How cold is your water temps - does your engines take a while to warm up - how old is your T stat - how old is your anti freeze all this can effect engine running and the spark plugs is my point here.

Basically its just best to stay on top of it as much as one can on the complete engine side. Examine the spark plugs and with a spark plug reader to catch issues as well then go on from there. Fuel pressure is very important as well.