Too Hot

[avanti]

I have a 2000 Donzi 18 Classic with a 350 Mag and a Alpha 1 Gen2 outdrive. The problem I am having is that it has the Mercruiser factory fresh water cooling on it (the one that goes through the engine only) and the engine is running around 180 degrees up to about 4000 RPM. When we start running above 4000 RPM the engine temperature starts increasing up to about 200 degrees and the alarm comes on and stays on until the temperature drops back down to around 190. Should I replace the heat exhanger with aftermarket larger one ? This problem has been occuring since we got the boat. Any info would be appreciated.

[gcarter]

The heat exchanger needs to be cleaned.
Remove the end caps and clean the tubes. There are some steel brushes made that look like long pipe cleaners (at least this is how I think it's done) and they are run through the HE tubes. Running in salt water all the time, it probably needs to be done annually.

[joseph m. hahnl]

I have a 2000 Donzi 18 Classic with a 350 Mag and a Alpha 1 Gen2 outdrive. The problem I am having is that it has the Mercruiser factory fresh water cooling on it (the one that goes through the engine only) and the engine is running around 180 degrees up to about 4000 RPM. When we start running above 4000 RPM the engine temperature starts increasing up to about 200 degrees and the alarm comes on and stays on until the temperature drops back down to around 190. Should I replace the heat exhanger with aftermarket larger one ? This problem has been occuring since we got the boat. Any info would be appreciated.


you can try to clean it like George said. also check the sea strainer to see if it's obstructed. it should actually run cooler at WOT. This part is a definate. change the thermostat to a 160 degree . If it's running @ 180 it is to close to the over heat range. Also make sure you use coolant to top off not water.
water has a lower boiling point. If it's a full cooler "It also runs coolant thru the Exhaust manifolds they run extremely hot any way.

Last but not least the raw water pump on the drive may be tired and it isn't getting enough water to disipate the heat from the cooler.

Oh and No don't buy an after market you will encounter the same thing.
They all will over heat if you don't have good water flow thru the exchanger and or if your have low on coolant.




joe

[MOP]

It is always good to start with the basics, first take the inlet hose of the cooler and put it in a 1 gallon container. Start the engine at idle the pump should fill the container in about 45 seconds with a good pump. That will give you a very good indication of the pumps condition. Check the power steering cooler for debris, pull the end caps on the exchanger and check for debris in the tubes. Also feel the hoses in the sea water part of the system one may be getting soft Aand collapsing more common then most think. If you are running stock iron exhaust? If they corroded up in the riser that will restrict the water from getting out quick enough. The very last thing I would suspect is the exchanger its self they rarely give you a problem other then debri.

Phil

[BUIZILLA]

let's talk about the impeller condition... :garfield:

[avanti]

The impellor is brand new. I think after reading the replies, I will pull the heat exchanger tomorrow and check for debris and clogging as the boat does not have a sea strainer between the outdrive and the exchanger. Thanks for the advice, I appreciate it.

[mrfixxall]

Check to make sure the tube from the impelller is all the way attached,,,or your thermostat is sticking....

[MOP]

You have power steering so you have a small cooler between the drive and the exchanger which usually plugs up first, you may even find parts of an old impller, barnacles, grass etc in there that will plug up first! If you remove the hose on the drive end and the one going to the exchanger you can back flush it from the exchanger end. Also no need to remove the exchanger to inspect it, you can pull the end caps off hold a light at one end then look through from the other. Like I said earlier I will be damn surprised if you have an exchanger problem! By the way the Merc factory exchanger has about 20% more capacity then what the engine needs

Phil