Prop Size, RPMs, & overheating

[jongolds]

I've finally got some time in my new to me 73 Tsunami with a 96 Merc 225. It's got a 15 1/4" x 15" SS prop. RPMs top out at 5k and prolonged running at 4k causes it to overheat.

I'm still working on getting a manual so I'm not certain but I think I should be topping out at a higher RPM. What do all think? Also, could running with to much pitch cause you to overheat? I've never heard of that before but intuitively it kind of makes sense to me.

I havne't changed the impeller yet. I know I should but I was told the previous owner had done it before selling it last fall so I was hoping to be able to cut that corner this seasons. I know that's not the smartest thing but there is only so much time in the day and I'd rather spend it on the boat than working on it.

I'll need top get a new prop to have a spare anyway so I'm thinking about what to try. I'm open to the idea of a 4 blade too.