So I am getting ready to perform the spring maintenance on my boat which has a fresh 509 in it with about 8hrs from last season. I have always run MR43T's in all my marine engines but I read an old thread about people running Rapid Fire #1 which is the platinum version of the MR43T's. My boat is on a lake where maybe it sees 10-14hrs of run time the entire season and almost no long durations of WOT, it spends most of those hours between 3 & 3,800RPM's With that said is it smart to switch to a Platinum or stick with the trusty Standard core plug?

The extra money for platinum's aint worth it to me considering i changed plugs yearly anyway! Just verify the plugs are looking good as far a the color goes burning fuel...you might consider going up or down in heat range....if need be but i would just stick to the basic stuff since you wont see any perf gains with just plugs lone

This is what I was thinking too just wanted your opinion.

You can run a lot of hours on a platinum or iridium plug, but it just irks me to pay $10-$12 per plug. Pulling the mr43’s give me a chance at inspection and compression test just to keep tabs.

I ran Rapid Fires #1's a long time ago. The only difference from them and MR43's was that they did not foul out at idle on my engine.

I just went with the MR43T's again they never gave me an issue so why mess with something that works.

The benefit of Platinum or Iridium plugs is reduced center electrode wear. The spark wants to jump at a sharp point. Rounded standard electrodes tend to round off and not be as effective at the spec'd plug gap.

Can often run wider spark gaps.

I've bead blasted my Iridium plugs to get the carbon cleaned off them...them they're good as new. The iridium tip is something like 4500°f laser welded on.

Nothing wrong with running what works for you. Just being able to change the plugs with engine mounted is a bonus.

Slight contortionist task in my boat but I'm a little person so I can cram back there to change them. Again my boat maybe sees 12-16 hours of run time a season and I think I'm estimating high.

Race prepped engines will often have the centrctrode filed to a narrower point. Only needed for a short time and creates t platinum and iridium effect

I wish I could change my plugs...even with a 3/8 batt ratchet won't get all of them.

Big gaps are more of a concern (issue) than anything else ignition wise.
Standard plugs / wires / caps / rotors / coils lead a very long time on marine engines with normal .035” gaps. Even the individual coil engines.