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270 Crusader overheating

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51Chris

New member
I replaced the engine block on one of my Crusader 270's and the engine is overheating so I'm looking for some advice. The block is new but the rest is from the original engine. The engine ran great for the first trip after the rebuild and overheated the second time out. Nothing appears to have changed.

I plan to look at the following things and would love any additional pointers

1) Thermostat
2) Radiator Cap
3) Raw whater Impeler (There is water coming out od the exhast port on the back of the boat, but I haven't compared the amount with the healthy engine yet)
4) Coolant levels. I put almost 4 galons of coolant in and there does not appear to be any leaks.

My temp gauge also decided to stop working. When I use the temp sensor from the other engine it reads below 200 yet coolant appears to boil.
 
23 quarts is the rated coolant capacity of the 350 ci crusader. Athough, that doesn't explain how you ran the first trip ok.
 
Good to know. I may be off on the 4 galons, I just kept putting coolant in untill I couldn't get any more in by massaging the hoses. I'll add even more coolant and see what happens. If I overfill it it'll just come out the overflow, right?
 
OK. Filled her up with more coolant and she appeared to have run fine, no boiling over.

The temp gauge is still not working. I tried the temp sender from the other engine in this one and it appears to be broken now as well. These are barrel style senders with a single wire coming off of them. Why do I keep breaking them? Could this be a grounding issue? I still have a couple of loose ground wires that I'm not sure were connected before I pulled the engine. What is the principle of operation for these senders? Are they a variable resistor? Google hasn't been much help :)
 
Temp sensor is a variable resistor (thermistor), and does depend on the thermo housing for ground. Note that some engines use a special thermo gasket that has brass eyelets to insure the ground path thru the gasket.
It's hard to kill the sensors unless they are dropped or maybe the stud is overtightened. Sometimes age will cause a crack or other defect in the sensor material (I think a carbon alloy).

Teflon tape is not preferred, use PST or similar paste thread seal.
 
Did you use the pre-diluted stuff or 100% antifreeze?

You can do the "quick check" on the gauge by removing the wire from the sender, turn the key on, and watch the gauge. If should sit on the left peg, if ok, ground the sender wire and the gauge should sight on the right peg (hot). If the gauge isn't working, the sender doesn't matter. Like Dave noted, many senders have died from too much torque on that nut.
 
I used the diluted stuff. I have a new data point. I took the boat out on saturday and ran with no problems under low to medium load. When I got to my destination I idled for about 5 minutes and she overheated again. My idle is set around 650 rpm. Could it be that I'm not getting enough water in when at idle because the idle is set too low? What esle would cause an engine to overheat when going form running at 2500 rpm to idle?
 
51Chris said:
When I use the temp sensor from the other engine it reads below 200 yet coolant appears to boil.
Click to expand...

This statement might be revealing. If combustion gas is leaking due to a head/gasket defect, you might see this. You need to know with certainty your water temperature at the thermostat housing. Reading the dash gauge is not the approved method with an unknown system. Get a IR thermometer and then know for certain. Up to about 170 deg is normal at cruise power with a closed system.
 
oh and both temp sensors are broken now, I guess I must be overtorking them :) New ones should be here Wednesday...
 
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Ok, I replaced the thermostat and the radiator cap. Running the boat at about 2500 rpm for 15 minutes barely touches 170 at the thermostat housing with an infrared thermometer. When I throttle down to idle temp starts climbing. I shut the engine off when it got to 195. What is the upper end of the temperature band should I expect? This looks to me as an insufficient water flow at idle issue. How can I check my incoming water path without flooding the boat :) do I have to get my diving gear out?
 
So the block is new but the bolt ons are from the original....how old is the original stuff, particularly the exhaust elbows?

I'd say you have a restriction that isn't letting enough water out when the pressure subsides due to the engine rpm reduction, but that's just my guess.

I'd start with the pump - you can measure its output with a bucket and a second hand on a watch. If the pump is okay, I'd expect the elbows have clogged, not completely but just enough to do the overheat after running. If the pump's output is less than spec, do like DD said and take a peek inside.
 
Try this test (and it's not as dramatic as it sounds): Remove the hose coming OFF the raw water pump and aim it where you can allow water to go. Start the engine and let it idle. If the flow resembles what you'd see pouring water rapidly from a gallon can, then it's probably moving enough water.

Seeing that you have twins, and assuming the other motor is okay, you could repeat the test on that one and compare. This test eliminates lots of speculation!

Jeff
 
If its an older cruader, it uses the sherwood E-35 pump. I've posted its characteristics a few times on this board; I'm sure a search will find it.

It was obtained from Sherwood's tech department along with some "missing" information (details) about the test setup used.

If you can't find it, I can send it along but won't be until next week.
 
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