After having solved the issue with the boat not planing out (spark plug wire off and fouled plug) now the oil temp is running high. I changed the plugs before the weekend and took it out Sat. and at higher rpms the oil temp steadily goes up until the alarm light comes on. I was able to back off the throttle to get the temp down but still runs at about 270-280. As soon as I go to idle the temp comes down quickly to around 170. Any ideas what could be causing this issue and what temp should I be seeing?

Check your impeller, oil cooler for for blockage , also t stat.

Verify good water flow and clean oil cooler as stated above .A bad / defective / incorrect oil filter will cause high oil temps without high eng temp by restricting flow through cooler. Replace oil filter and cut open old filter to check for debris or collapsed element. Also verify correct oil level ( to much will cause aeration , which can lead to high temps ) . Check all external oil lines for kinks , damage . ect. GOOD LUCK !!!

I have a 454 MPI, running hard, say over 4K, I see 260+.

Normal running 170 or so. Never threw an alarm.

Ken

change the oil and filter now, oil may be diluted from fuel from that non firing cylinder...

I've seen you parked in some pretty shallow water - assumed that you walked boat in / out. That boat has a LWP drive, and does not perform well at all in shallow water. As previously mentioned, I'd bet that you're oil cooler and or power steering coolers are clogged with river mud and/or pebbles. That will cause severe overheat condition and will cook your motor fast. LWP are not beach friendly.

Have you pulled the hoses and confirmed the holes/tubes in the coolers are clear?

Yeah, I was aware of the low water pickup on that style outdrive. For that reason, I always try to walk it out until deep enough or even get shoved off the beach. Unfortunately I've found several problems while trying to figure out the problem. However, the reason for the oil temp was due to water in the oil via 4 leaking ports on the headers.