FWC fresh A4 cooling problems

[rjkerby]

I have had cooling problems in myA-4 powered Catalina 30 since I've owned it. I've just rebuilt an A-4 and had the block bored and cleaned. All my pumps,both fresh and raw have been refreshed. Water has plenty of volume at the exhaust. Replaced heat exchanger with a new Moyer supplied unit, new Thermostat and the Moyer bypass is closed. Have the Moyer thermostat kit. Replaced the exhaust manifold with a new unit and the exhaust riser .
At 1800 RPM it runs at 190 degrees. I've replaced the temperature gauge and sending unit also. I've just installed an Indigo prop , 10 X 7.4 three blade and at 1800 the boat is doing 6 knts. max rpm is 2000 and at that rpm temperature runs closer to 200.
Is this what it's supposed to do with a 160 deg. t-stat or does anyone know anything else I can do to get the temperature down toward 180 range

[Al Schober]

You shouldn't be running that hot. Is your temperature gauge accurate?
I'm running the Moyer FWC cooling kit, have no thermostat, and the temperature barely moves off the cold peg. As a first step, I'd try removing your thermostat and closing off any bypass. If that doesn't bring the temperatures down, you're going to need an InfraRed thermometer to get some temperatures - block in, manifold out, sea water in, sea water out.

[Mo]

You shouldn't be running that hot. Is your temperature gauge accurate?
I'm running the Moyer FWC cooling kit, have no thermostat, and the temperature barely moves off the cold peg. As a first step, I'd try removing your thermostat and closing off any bypass. If that doesn't bring the temperatures down, you're going to need an InfraRed thermometer to get some temperatures - block in, manifold out, sea water in, sea water out.

I agree with Al...take out the T-stat and see what happens. There are a few around that described similar situations as yours....

[hanleyclifford]

A thermostat is one of the biggest obstructions in a cooling system. Just look at it objectively and consider the available cross sectional flow surface both with it and without. Successful use of the thermostat requires a very efficient exchanger and the ability to tolerate a much slower flow rate for the antifreeze.

[Nauti Buoy]

Im having similar issues with a re manufactured MMI engine just installed. New pumps, acid washed Sel Den heat exchanger, good water flow, cleaned mixing block and muffler. Exhaust lines elevated with no valleys, laser temp checked block at temp sending unit.
Block temp corresponds to to water temp gauge, 195º at 1200 to 1500 rpm, 200º at 1800 rpm and 210º+ at 2100 rpm.

97 deg day first sea trial, 100 deg today.

Not sure what to think.

[hanleyclifford]

Im having similar issues with a re manufactured MMI engine just installed. New pumps, acid washed Sel Den heat exchanger, good water flow, cleaned mixing block and muffler. Exhaust lines elevated with no valleys, laser temp checked block at temp sending unit.
Block temp corresponds to to water temp gauge, 195º at 1200 to 1500 rpm, 200º at 1800 rpm and 210º+ at 2100 rpm.

97 deg day first sea trial, 100 deg today.

Not sure what to think.

Take the thermostat out and run engine. Make no other changes. See what happens.

[JOHN COOKSON]

You might also check the raw water intake valve on the through hull fitting to be sure there are no obstructions to the water flow to the pump in the plumbing.

TRUE GRIT

[hanleyclifford]

FWIW. There is a significant flow advantage to be had by getting rid of the "hard 90s" and replacing with "street".

[joe_db]

The "other firm" has what looks like a much better thermostat too.
I would check without one first and see how that goes and also pinch off the bypass while you are trying this to get full flow.

[zialater]

Ditch the thermostat

I have had cooling problems in myA-4 powered Catalina 30 since I've owned it. I've just rebuilt an A-4 and had the block bored and cleaned. All my pumps,both fresh and raw have been refreshed. Water has plenty of volume at the exhaust. Replaced heat exchanger with a new Moyer supplied unit, new Thermostat and the Moyer bypass is closed. Have the Moyer thermostat kit. Replaced the exhaust manifold with a new unit and the exhaust riser .
At 1800 RPM it runs at 190 degrees. I've replaced the temperature gauge and sending unit also. I've just installed an Indigo prop , 10 X 7.4 three blade and at 1800 the boat is doing 6 knts. max rpm is 2000 and at that rpm temperature runs closer to 200.
Is this what it's supposed to do with a 160 deg. t-stat or does anyone know anything else I can do to get the temperature down toward 180 range

I had the exact same problem. FWC cooled and running around 180 to 200. I finally solved it by following the advice of multiple posters here - I pulled out the stinking thermostat - and voila! 140 to 150. Give it a try.

[hanleyclifford]

Just to be clear on this; if removing the thermostat causes your temp to drop from say 190-200 to 140-150 this does not automatically mean there is anything wrong with the thermostat per se. It could mean simply that the thermostat was too much of a restriction for the rest of the cooling system to cope with. The thermostat might have been functioning as intended. IMO flow, both volume and velocity, is the key to a successful cooling system. That is why I currently use a bypass loop and street fittings everywhere on the engine. But I am contemplating a return to the thermostat method and will be looking for the best flow unit available and possibly retention of the bypass loop. Overheating is only one mischief that results from low, slow flow. In any case I do not allow my engine to run below 160 for sustained periods. FWIW

[joe_db]

http://www.atomic4.com/thermostat.htm

This one?

[JOHN COOKSON]

The goal is to cool the engine properly and get a satisfactory reading on the temp gauge.
There are many different opinions as to what the proper operating temp is as read on the gauge in both RWC & FWC A4s.

TRUE GRIT

[joe_db]

Conventional wisdom is a FWC A4 should be at 180 F. The hotter the engine the more efficient it is, the less oil contamimination, and the less gunk on the valves.
Car engines use pressurized coolant and frequently run around 200-210 degrees for these reasons.
I am not 100% sure I agree for a few reasons. Reason 1 is not about the engine, but the boat. A 180 degree engine puts WAY more heat in the boat than a 120 degree engine. The oil is another issue. IMHO a 180 degree engine may overheat the oil if you do not use an oil cooler. My current engine runs too cold - it barely moves off the peg unless run full blast all day in warm water - but it does not seem to suffer sticky valves or dirty oil. I am thinking through FWC and may elect to run cooler than 180 after I set it up. Not sure yet.

[rjkerby]

more on cooling problem

http://www.boatfix.com/how/cooling.html

Interesting page. I've checked the outlet of the coolant pump(inlet to the block) and the outlet from the exhaust manifold, inlet is at 130 deg and outlet is 185 deg with a laser heat gauge. It seams the exchanger is working as it should according to the above article.
I didn't realize that the rating of the stat was the opening rating and the run rating would be as much as 20 degrees hotter

From Moyer's catalog:

Product No. - CSTH_01_510
Single-action aftermarket thermostat, includes gasket

This stainless single-action thermostat maintains a temperature of approximately 160 to 170 degrees in RAW WATER cooled engines, depending on the temperature of the outside water, the load being imposed on the engine, and of course the condition of the water pump and the water jackets. In FRESHWATER cooled engines, temperature will settle in between 170 to 190 degrees, depending on the above variables plus the efficiency of the heat exchanger.

This thermostat requires a 1/4" spacer to provide adequate clearance between the top of the thermostat and the underside of the thermostat housing. If you are changing to a single action thermostat for the first time, you can select one of the conversion kits below.

Single-action thermostats also require a method of controlling the flow within the bypass loop in order to provide the necessary flow through the block and head to enable the thermostat to regulate temperature within normal range. If you do not already have a valve in your bypass loop, you can find one in our online catalog with a product number of CSOT_01_61