TEMP HORN GOING OFF AT HIGH RPMS

[CARL]

I have a 2000 28 Daytona Eliminator w/twin 1999 2.5 offshore sports. Port motor had powerhead replaced after 20 hrs. Injectors 5&6 were not spraying. New powerhead is heating up to 180 at 5000 rpms and above and setting off horn. Water psi is 12 - 20 at these rpms. I have run the boat with the restrictor plate washers removed and also the plastic fitting removed from the pee tube out the cowling
allowing no restriction. Motor runs normal temp and (140 - 165). Mercury recommends I increase the diameter of the restictor plate in each hose coming off the top of each head. THIS DOES NOT SEEM RIGHT!! Looking for some help. Please advise.

[us1]

You can’t run no washers at all in the heads and you need 15 lbs. minimum at WOT. I run 1/8 fender washers ( hole in washer is bigger than 1/8) and put the plastic restricter back in the dump tube. All the stuff you removed will make it run hotter if the rest of the cooling system is in proper working order. What set up is on the other motor and what is the pressure.

[CARL]

Starboard motor runs to Mercs specs 150 - 165 @ 4500rpms and higher. No problem with this motor. My problem only started after new powerhead was installed. Boat ran fine when first delivered. Is this for me to be doing thr r & d or why is Merc not correcting the problem.

[MERCMAN]

sounds to me like someone screwed something up replacing the powerhead. you could have a leaking pan gasket(leaking internally) or they might have left a tool in the exhaust adapter?(lol) (just kiddin , i hope) you never know , ask them if they dropped the lower unit when they replaced the powerhead , they could have one of the water pipe seals pinched into the water tube. sounds like your motor is not getting enough water! but low and behold you could just need to make the washers smaller , if the water is leaving the motor too fast the heat wont have enough time to transfer. i have never had one that needed smaller washers than merc installs from the factory , this sounds like a patch job to get you going. tell them to fix it right!

[us1]

Usually I run bigger washers than for the factory (1/8 fender) to lower head temps but to remove washers/ thermostats altogether makes the motor do all kinds of funny stuff.

[MSCLE]

I HAVE THE SAME PROBLEM AND NEED HELP!!!!HORN WENT OFF AT 5500RPMS,16POUNDS WATER PRESSURE.......5000RPMS,14/15 POUNDS,4000RPMS@12POUNDS WATER PRESSURE...IT ALSO WENT OFF STARTING IT UP AND STEPPING ON THE PEDAL...WITHIN 4 SECONDS AFTER CRANKING IT UP!!!!!!!!IT EVEN ALARMED TRYING TO GET IT ON THE TRAILOR...STEPPING ON THE PEDAL AGAIN!!!!!!!!EVERYTIME THE HORN WENT OFF I FELT THE WATER COMING OUT THE ENGINE.....IT WAS NEVER HOT TO THE TOUCH!!!!!NEVER!!!!!SO THE LAST TIME THE HORN WENT OFF AT 4000 RPMS I TOOK THE COVER OFF AND FELT THE HEADS......NEITHER SIDE WAS HOT!!!!!!!MY FUEL CURVE IS 0%...I LIVE IN SOUTH LOUISISANA...THE MOTOR IS ON A STROKER...I HAVE GOOD WATER PRESSURE........ANY SUGGESTIONS.....WE ARE GOING TO HOOK IT UP TO THE DDT THIS WEEK FIRST CHANCE I GET........I AM READY TO SEND THIS THING SOMEWHERES TO GET IT RUNNING RIGHT!THANKS FOR YOUR HELP......SCOTT PLAISANCE

[us1]

You have an electrical short in the heat horn system.

[CARL]

Earlier reply talked about some possible improper install of my powerhead. I have had these thoughts all along. It doesn't make sense to me that MERCURY would have this going on. And also to have the dealer make various adjustments till running right.
Anyone agree? Dealer could just be telling me whatever they wish. Im looking into it further. And if anyone knows how a consumer can contact Mercury or get the info on my case history to see what Mercury really knows about my problem please inform. Thanks all, help so far has been great!!!

[AlaskaStreamin]

(920)929-5040. Keep this # around. It was given to me on the sly from a dealer. The guy I got was VERY helpful and wanted to make things right with the Optimax on our harbor patrol boat.