Anyone remove the factory circulating pump & replace with a crossover on a 454/502 MPI merc motor?

depends on the brackets and belts/pullies your running
i had to run one unless i wanted to pony up some serious bucks to change everything
so what i did was to remove the impellor from it and seal it back up, they take about 30 hp to run,
i just run the merc sea pump

So you just pull the impeller right?

is it worth all the hassle on a stock motor set up for maybe 25-30hp?

This is a interesting topic to say the least. It has been discussed many times on the technical Forum. The first thing I found out is that 25to30 HP is a Extremely far stretch as far as HP gains. The second major problem people talk about is water pressure amd plumbing in water dumps and relief valves. I personally have put one on a 365 Magnum , carbed and noticed no gains other than cosmetic " Cleaned up the front of the engine" . When i started hearing about water pressure issues and blowing out intake gaskets and the like it scared me. I switched back to a circ. pump. I have seen many engines on this site with crossovers and it didn't appear tha they had water dumps or relief valves and they must run just fine . Ihave ask the question before about crossovers being just a direct bolt on as advertised and could never get a straight answer. If you need relief valves and water dumps with crossovers why dont the companies advertise them like that . Just my 2 cents

A huge can of worms for 5-7 hp.not 25-30

yes when people say 30 hp just look at the fractional hp belt that drives it and you realize it prob less then a few hp
I did mine and it looks good but no real performance in crease

For once I agree with Birdog


Not to mention you typed "just remove the impeller right?" Uhhm NO please do a search in the Tech section. You may want to enjoy your Turn-key boat and look elsewhere down the line for speed gains.
You may want to have your props worked on for a nice change without spending too much and having engine damage or hotspots.
Call one of the board prop sales/repair sponsors and work with them on custom work. I use Throttle-Up and have heard great things about B-Blades.

Props are done, drives are done. I just have a case of winter "what-ifIdidthisitus". I'm getting ready to rebuild the engines at the end of this 2006 season. So I need to gather ideas & parts early so my wife doesn't have a fit this next winter.

In that case......................I'm changing my mind.....