After two years of heat soak problems and at least 7 trips to dealers the heat soak problems may be fixed but a cause not found as yet.

The dealer had this motor for the last three days. Re-tuned everything and ran in gear for hours at a time. Noticed water from pee-hole hotter than other Hondas.

Took out thermostat and ran motor without one and instantly the motor ran much better. No cough or miss at idle.
He replaced plugs with equivalent iridium plugs as well.

I picked boat up and took out for a run. This is the first time since new that there was not one miss / cough or splutter throughout the rev range. After letting a heat soak to occur I turned motor on and it went straight into a smooth idle. All fixed on this occasion.

I know the proof with be in the next couple of months as we approach summer.

Is there any damage caused by not having a thermostat.???

One benfit of a thermostat is even temperature of the engine. Running without can allow "hotspots) A four stroke is less prone to this as the oil circulation distributes heat around somewhat. I'd keep looking for the cause of the problem.

Only had the outboard out one time so far, but the vapor lock/heat soak idea sounds about right for my engine as well. Started fine ran a few miles (outran some skiboats with a 15hp HONDA!) and slowed down then she stalled.

Took about 30 minutes and some blisters to pull start it up again. Brand new water pump impeller - peeing like a champ at all RPM's. Had to mess with the choke (full choke at lowest throttle setting) to get it to start and get in in drive as fast as possible. Then it would backfire a few times as it was ramping up, cleared up then and ran like it did earlier - until I throttled back again.

Rather than removing the T-stat outright, I'm going to try drilling a few holes through it first (the concept worked good on older diesels).

Pretty impressive thing these Hondas - not too many complaints and very few references to PROBLEMS with them on the internet...