496 HO's heating up in 28 Daytona
 

Hello, I own a 2001 28 Eliminator Daytona with twin 496 HO's that have been heating up, starboard side mostly. Here's a quick history, had both impellers replaced late March and ran the boat for a weekend at LOTO and every once in a while the starboard engine temp would rise to 180 deg. and beep after running and then coming to idle. I would then put shifter to neutral and rev up motor a bit to get things flowing and then temp would come back down. This problem has been happening intermittantly (not all the time) to this day. A few weeks ago I ran the boat on the Missouri river and the motor was heating up all day if I went over 3000 rpm. I removed the end cap on the heat exchangers and found a bunch of debris, so I cleaned it out and have since ran the boat at LOTO with no problems, then just yesterday ran the boat on the river again for only 5-10 mins. and the darn thing was heating up again, so I checked for debris in the exchangers and there was nothing. This thing is playing with my head. The 496's are notorious for heating up with the sea pump design. Has anybody had this problem? Would the high x-dimension and low water pick ups on this boat play a part in the problem? It's really starting to get old worrying about it. What should I do?

thanks,

Todd Harper

Re: 496 HO's heating up in 28 Daytona
 

Todd,

The first thing you need to do is install water pressure gauges. If you are running hot over 3000rpm and you think the X is too high, you will be able to read your gauges to determine that. I would start there. You can get a remote gauge and tap it into one of the plugs on the intake. Have someone read the guage as you accelerate. This would be the easiest thing to do to determine if you have a high X dim. Are you also running shorties or standard?

Re: 496 HO's heating up in 28 Daytona
 

Try running it with an engine flusher attached and see what temps you get. If one engine is running cool you would think the pick-ups are fine. Check the usual stuff like coolant etc. Maybe try swapping thermostats? Check if Merc has a bulletin out?

Re: 496 HO's heating up in 28 Daytona
 

Not sure if your motors are old enough (I would imagine they are in a 2001), but there is a recall on the earlier motors with the water rail on the ehaust manifold. Dissimilar metals were used and cause galvanic erosion, especially when in salt. Also, using the software I bought from rinda technologies will show me sea pump pressure in real time along with a lot of other cool stuff.

Re: 496 HO's heating up in 28 Daytona
 

Check your oil cooler to make sure there isn't any debris in that. I had a piece of an impellar fin get caught on the inlet side of the oil cooler. The engine ran fine below 2000rpm but anything above that and it would get hot because it couldn't flow enough water to keep the engine cool.