3.0lt high exhaust temps

[concept19]

gday mates....i have a merc 3.0 225 on my 19 foot concept it has a standard mercury recon power head with a 4 hole 300 intake,a set of reeds ,shortened exhaust stub,twin pyros,drilled gearbox,6800 rev limit and a remapped fuel ecm swinging a 30"chopper and it made 246 hp at the prop. now the prob has been extremely high exhaust temps(as high as 1600 f ) i replaced the fuel ecm with one programed for a ported 300 and the temps have come down to 1330 ish wot and i rekon these are still a bit high. fuel pressure at wot is 35psi ...i am a bit aprehensive to use the boat as i dont wana torch a piston.i have removed the heads and cant see any dramas but will be pulling the slugs out as a precaution anyhow......so i ask u guru's is the fuel pressure too low. i am gunna put on an adjustable reg and bump it upto around 40psi to try cram some fuel in there to cool it down..fuel used is 98ron at 40;1 . any idea's

[stoker2001]

i suggest contacting eric simon at simonmotorsports.com he specializes in 3.0 mercs

[sosmerc]

I like the idea of your "adjustable regulator". It certainly would not hurt to bump the pressure some and see if the extra fuel cools things down. Tony needs to get the PCU ready for the 3 litres!
Eric has a way to modify the flywheel so you can run a standard ADI system such as the Laser EFI motors use....then a PCU could be used...and THEN you should have total adjustability.
It probably won't be long before we no longer have anything we can really "play" with as far as adjustability or modification......everything will be factory set to meet EPA standards and that's that. Start saving all your old stuff, guys!!

[r.c.]

you did not mention what year model motor you are running. the engine is running way lean. you did say that you had the ecm remapped.with the mods you have done the ecm for a 250h.p. should have been enought fuel. the 95+96 model ecu+ecm's are not as good as the 97's. the 97 fuel management and ignition controls allow a better fuel curve and an additional 4 degrees spark advance a w.o.t.. the stock control boxes of this model the rev limiter starts taking over at 5800 rpm's by reducing the spark advance by 2 degrees,at 6000 it reduces 2 more degrees and at 6400 the spark advance goes to zero. these 3.0 225's was designed to be a low end brute . the adjustable fuel pressure regulator would probably the cheapest way to solve your problem. check the manual to confirm this, disconnect the air temp. sensor to increase fuel by 10 percent. do not bypass it , bypassing the sensor decreases fuel by 10%. this will be through the entire rpm range. maybe this can help. dewitt deweese is a merc. guru in miss. #601-853-1007 . most of this info came from him. i believe he is a member on s&f.
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