Merc Cruiser Alpha 1 overheating

[Jersmom]

We have a 1990 Merc. Cruiser Alpha one inboard 4.3 liter. Overheats. We've determined it's not the lower pump, the thermostat or the flange. Could the exhaust elbows cause problem. Not sure how they work..

 

[Haut Medoc]

Re: Merc Cruiser Alpha 1 overheating

Welcome to Iboats... You don't say whether you have raw water cooling or a closed system... The answer in either case is yes they can. The water ports can become clogged resticting the coolant flow, especially in salt water operation. The best thing to do is take them off and have a look at the water ports.....J

 

[Jersmom]

Re: Merc Cruiser Alpha 1 overheating

It is raw water cooling. Is there a way to test for that? How would I know if they're clogged?

 

[Haut Medoc]

Re: Merc Cruiser Alpha 1 overheating

Your motor would over-heat! If you are sure that you have enough flow from the water pump, this is the next place I would look. Unfortunatly, there isn't a test for that. You have to take them off & inspect them. How old are they? Barnegat Bay is salt water and things will get crusty ....J

 

[Jersmom]

Re: Merc Cruiser Alpha 1 overheating

Thanks for your help. We'll check all that this week-end. I don't know where Barnegat Bay is, we run on the Missouri River, not salt water.....

 

[Haut Medoc]

Re: Merc Cruiser Alpha 1 overheating

Does it over-heat while idling, running hard or both? Will it cool down if you idle?...Describe the conditions that make it over-heat....J

 

[Haut Medoc]

Re: Merc Cruiser Alpha 1 overheating

Salt water or not this is where I would look next.........Tought it said Jerseymom.......J

 

[Jersmom]

Re: Merc Cruiser Alpha 1 overheating

Usually once it starts to come up to temperature, the gauge will go to zero, whether I'm running hard or not. When I shut it off, I can hear water boiling in the engine.

 

[Haut Medoc]

Re: Merc Cruiser Alpha 1 overheating

Could be the thermostat I suppose...Would't hurt to change that, relatively cheap and easy. These tests can be done on 'muffs'right in your driveway. Do the t-stat first, because its the easier of the two. Make sure you have the proper t-stat 142* or so, and get new gaskets for the risers. Do not re-use them Torque riser bolts to 25#. 20 for the t-stat..Post back and let me know how you made out......J

 

[Richard Petersen]

Re: Merc Cruiser Alpha 1 overheating

I have heard that a engine that boils the water out of the area where the temperature sender is will cause the dash gauge to suddenly drop to 0 degrees or show no temperature. Sounds like your problem. Don't keep running the engine this way. You are killing it. Get a good boat mechanic to find and fix it . Later is going to cost you a rebuild.

 

[llerrad]

Re: Merc Cruiser Alpha 1 overheating

Sometimes when an engine boils water and the gauge slams to 0. You can have steam (air) caught at the stat and the temp send. will not pick up the steam sometimes the steam at the stat can be caused by a blown head gasket or crack in head. As you point out the engine is getting up to temp which is before the stat will be hot enough to open.

 

[Uncle Dave]

Re: Merc Cruiser Alpha 1 overheating

Jersmom,<br /><br />My .o2 says the riser (exhaust elbow) is the problem or where it connect to the manifold. Not hard to remove and inspect.<br />Good luck,<br />Uncle Dave

 

[Jersmom]

Re: Merc Cruiser Alpha 1 overheating

We removed exhaust elbow's yesterday. Really a mess. Looking to replace. Hopefully that will take care of it. I'll let you all know.....Thanks for all your input....