Looking at A 4 in San Juan 28

[capndar]

Looking at an A 4 in San Juan 28...engine seems to run ok for a while(30-40 min@ 80%), but then temp gauge goes to hot....suggestions?

[Don Moyer]

We'll need more information before we can help.

Don

[capndar]

Thanks! What else can I tell you about it?

[Don Moyer]

Do you have an early or late model engine? How hot does the engine get? Have you made any observations other than the temperature gauge? Has anyone worked on the cooling system lately?

Still shooting in the dark regarding the above, here are a few general suggestions to get you started in troubleshooting an overheating condition,
assuming that you have a late model engine.

Check first to see if you have a normal flow of cooling water coming out of the exhaust. A normal flow of engine cooling water will usually be sufficient to build up a head within the water lift muffler at idle to overpower the exhaust pressure, and result in a "batching" of the water out of the exhaust every second or so.

If you do not have a normal flow of water through the exhaust system and out the back of the boat, your water pump could be too weak to provide sufficient water flow; or you could have a restriction in a location that can limit the total flow of water. Examples of these restrictions include a blocked raw water through-hull, a piece of broken impeller in the elbow on the outlet of the water pump, a clogged manifold, a blockage in the inlet
fitting to the exhaust system, etc.

If, on the other hand, you experience overheating while observing a normal flow of water out of the exhaust, you will have to look for a restriction that is preventing water from entering the block, and preferentially moving through the by-pass hose instead. Examples of such a restriction are a blockage within the "T" fitting, blockage in the diverter cap inside the center of the water jacket side plate, or a thermostat that is stuck in the closed position.

You can trouble shoot the extent of a blockage in this location, as well as getting some short term relief, by clamping the bypass loop partially closed with a pair of pliers or a small "C" clamp.

NOTE: The bypass loop is the hose between the "T" fitting in the center of the water jacket side plate and the inlet to the thermostat housing. The short hose on top of the head between the thermostat housing and the manifold is not part of the by-pass loop.

If the flow of cooling water out of the exhaust reduces significantly as you clamp off the by-pass hose, the restriction would be quite serious and will probably require removal of the water jacket side plate and/or or the thermostat for further inspection, cleaning, or replacement. In the case of lesser restrictions, one of our customers was able drill an 11/32" hole through the center of the "T" fitting and tap it with 1/8" pipe threads. He was then able to connect a garden hose to pressure flush the "T" and diverter cap to restore good flow. After flushing, he installed an 1/8" pipe plug in the hole.

Regards,

Don

[capndar]

Don

I looked at the boat and engine...I believe it is a sad little motor...the port side of the engine (above the carb)...the bolts and the head on that side are really rusted....the head on the starboard side (just on the othjer side of the spark plugs) is still a copper color paint - that looks to me like it got REALLY hot on the port side....it appears the head has been 'repaired' with JB Weld or similar on the starboard side about 4 inches down from the top of the engine....it did start, but throttle problems prevented any extended testing...I believe if I get this boat, it will be a new/rebuilt a 4.

Is my anaylsis on the rust/heat in the right area?

Mike