Well, if it's overheating, the overheat alarm will come on as well as the light on the tach.. No one mentioned an alarm sounding during the problem.Is it safe to assume that it worked when the ignition was turned on and it went through the self-check process? As far as SLOW, that feature doesn't kill 3 simultaneously. It will cause a breakdown of all cylinders as though all cylinders were misfiring. A V6 will drop 3 cylinders on the starboard side for shift-interruption; on the port side, if the hidden diode pops, you'll lose that side. The same is true for a V4, just 2 fewer cylinders. But SLOW activating for overheating on either engine will make certain you shut down to see what's going on! So, my reply was based on 1) erratic running at full throttle; 2) smooth running at part throttle; 3) return to erratic after a period back at full throttle; 4) no mention of steam, lack of water discharge, or overheating smell; 5) no extended period of stable reduced RPM at any level.
All that said, there's no reason not to check the head temps, but I hesitated to encourage someone who might not have the experience to go buy a pyrometer and hang out over an engine running 6000+RPM on a boat I don't know who the cap'n is, or the boat's handling characteristics while there's a shift in weight.
As far as a rev limiter not kicking in on Cap'n Bob's, it's only a rule of thumb about the RPM. Some of the powerpacks are rated to 6700, so yours might have kicked in at 5100 or 7400, or whatever RPM your engine's powerband indicated. Check the powerpack itself to see the RPM limit. Check the engine plate or owner's manual for the operating RPM. Though your engine can turn 6200, the power band is a Bell curve. If your operating range is 5000-6000, your optimum RPM is about 5500. Below that, you're not making the power available. Above that, your power decreases, despite the ability to turn RPMs.
Finally, I realize that petty officers don't make a career advancement "going off" like this, and I apologize if I've offended. But as a certified OMC/BRP tech with 57 years' experience, I've learned to try to answer the posed question with the parameters I've been taught, and try not to endanger the owner not knowing his capabilities. I have been wrong in the past. If there are specific RPM readings I can work with, or it's determined there is no tach or warning buzzer, then that knowledge may affect my answer.
Again, my apologies for any offense that may have been taken, or incorrect response based on the presented problem. We old folks can be crotchety.
