Overheat issues on 360 chryslers

SHORTFUSE · Post by **SHORTFUSE** » Mon Mar 31, 2008 6:49 pm

Hi this is my first post,been just watching fo awhile.I have a 1980 36 tri cabin,which was already, clean but I have really tried to fit it out.My problem is both motor overheat at about 2900 rpm.The impellors and manifolds and risers are very clean(yes on the inside).Both motors run at 160 at idle and are very smooth.What would cause both motors to do the same thing also the intakes are very clean.Could this be a timeing issue even though both motors will turn 4000 rpm smoothly. P.S sorry for the rant John

jimini · Post by **jimini** » Mon Mar 31, 2008 7:06 pm

Couple of thoughts here... why do you think its a timing issue?

Have you added anything to the hull infront of the engine cooling uptakes that would cause "air' to get into the water suction? How long does it takes to "heat up" does it heat up at 2400 rpm? 1800rpm? is higher the rpm the higher the temperature of the engines? how are the cooling discharge lines? are the props correct for the boat? does the props labor the engines? at 2900 are you planing? do you achieve full throttle range in gear and running? I can understand maybe one engine becoming warm but rarely two... what was the last thing you did before you started having this problem... I doubt if it happen overnight...or did it??

Safari · Post by **Safari** » Mon Mar 31, 2008 7:08 pm

It doesn't take much for the trans coolers to cause that issue - try backflushing them with full pressure from a water hose (I am assuming you have checked the obvious stuff......)

SHORTFUSE · Post by **SHORTFUSE** » Mon Mar 31, 2008 8:47 pm

Sorry for the lack of info.No it did not happen overnite,the boat was layed-up for 4years and I got a good deal as is.The props are the right ones I know because the boat gets on plane and runs at 4200 rpm.Both motors run real well at about 2900 rpm it starts to heat up,if I stay on the gas I can get about 25 kts.I replaced both impellars and pulled the risers apart(would have replaced them but they were newer) because of the long lay-up,before I used the boat.The motors were rebuilt in 2000 before it was not used for 4 years 175 hrs I have all the paper work,I talked to the shop they remember the boat but thats all.The only reason I asked about the timing is because Im runnin out of rope,the boat does not run like its out of time. Thanks John

jimini · Post by **jimini** » Mon Mar 31, 2008 9:53 pm

I would consider removing the thermostats and running it ... if it still heats up you know its can all the water it wants for cooling... How hot does it get temperature wise? 200Â°F more?

jimini · Post by **jimini** » Mon Mar 31, 2008 10:16 pm

FWC? Or Raw water cooled??

mr elevman · Post by **mr elevman** » Tue Apr 01, 2008 9:17 pm

have you checked the motor water pump and are you full of coolent or water or its like jimmini said pull the thurmostat

whats realy strange is its bolth motors do your motors share a seastrainer were still missing something

SHORTFUSE · Post by **SHORTFUSE** » Tue Apr 01, 2008 9:31 pm

Blocks are FWC but manifolds and risers are RWC.Have checked both water pumps on front of motors,coolant was flushed and replaced.Each motor has its own pickup and strainer,when I was winterizing both motors pulled the antifreeze out of the strainer and came out the exhaust. Thanks John

jimini · Post by **jimini** » Wed Apr 02, 2008 5:35 pm

How hot do the motors get at 2900 rpm? both temperature gauges read the same when overheating (port/starboard)? at 2900 are you on plane? if not on plane at 2900 the engines may be laboring to push the boat up and ontop they will pick up temperature rise doing that.. I will still put out the thermostats and run them at 2900 and watch what happens...

jimini · Post by **jimini** » Wed Apr 02, 2008 5:42 pm

what degree is your thermostat? 160? 180? 190? or hotter.... it will run at low temperature levels idling without any load on the engines but engines pulling is a different story.. engines will heat up to whatever the thermostat is set for... commonly around 180Â°F for a boat. Maybe the thermostats are stuck to open only so far from sitting for four years. Now they are not opening up enough to cool the engines...try new thermostats if you haven't already... check to buy the proper temperate range for that engine...

Stripermann2 · Post by **Stripermann2** » Wed Apr 02, 2008 6:20 pm

John, you said the intakes are clean. I will assume you looked at the grates under the boat...

I had a similar issue with my Trojan. Take the intake hose off of the seacocks for each engine, open the seacock. Water should flow pretty good out of them.

Mine was encrusted on the inside of the pickup below the valve to about 1/8", restricting the flow upon demand. Your boat will not overheat at idle but under a load and calling for more water flow, there won't be enough.

You can clean it out with some elbow grease. Hope this helps.

Dreamer · Post by **Dreamer** » Wed Apr 02, 2008 9:22 pm

I had a water pump on an old ford, that the impeller deteriorated on. The temp was fine at an idle. Under acceleration the temp would rise.

SHORTFUSE · Post by **SHORTFUSE** » Wed Apr 02, 2008 9:55 pm

At 2900 RPM boat is on plane and not laboring,temperture is slowly climbing I pull it back before 200 .Thermostats are 160 I will probably take them out and try that.The intakes are very clean I have taken the seacocks and strainers apart. Thanks John