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Crusader cooling problem

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rodster4843

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My 350 fresh water cooled fuel injected engine is about four years old and has the red light buzzer set up and goes off ( though intermittently) when engine runs over 1600 rpm's. Belt seems tight, cap's good, full size raw water canister strainer is clean ( but seems not to fill up at times), seems to have a plenty of water exiting both exhausts, thermostat is opening, impeller looks like new, gauge is reading around 150 (even when having the problem) and the water tank is hot on each end but cool in it's center. The P105 raw water pump has a slight drip from the shaft ( about two drops a second ). I purchased a new one and plan to put it on tomorrow. As I've said sometimes it will run fine and when the buzzer goes off it starts missing and we can't run over 4 knots (limp mode). Anyone have any ideas, thanks, Jack
 
The temp sensor for the engine control computer (that is sending the alarm and cutting the power) is located on the left side of the intake manifold (if it is like mine) where it is reading the water exiting the left cylinder bank and the temp sender for the gage is located on the right side of the manifold where it is sensing the water exiting the right cylinder bank. So it is possible, but unlikely, to have different temps at those locations. For example you could have poor coolant flow and for whatever reason it flows better on the right bank than the left (it did happen to me, never figured out why). The computer thinks you have an overheat at its sender, and you likely do. First step is to order an IR gun that will read the temps at any location in the engine. They are on the internet for $50 to $70. Then you can shoot the spots next to the sensor and the sender and figure out what is really happening. I think the raw water strainer should be filling up so that sounds like it could be a suction problem with the pump (bad pump, clogged intake below the filter, collapsing hose, etc.). When you see it is not full you could pull the zinc out of the heat exchanger when the motor is running and see how much flow you have. It should be like a garden hose (and it is not hard to stick the zinc quickly back in. If you have a second engine the IR gun will quickly point out the differences as to what is hot and what's not.
CaboJohn
 
Depending upon where you boat and how often drives a lot of possibilities...

Like john suggests, that IR temp gun will help a bunch.

can you touch the exhaust elbows when the horn goes off? if not and they are cast iron, they are likely due for a replacement...Most replace the risers, too, if so equipped...
 
Replace pump if it is dripping it can also suck air. Water with lots of air doesn't disperse heat. But an IR gun is very useful.
I read somewhere on this forum when I was having a heat problem is start from checking from the seacock toward the engine.
 
Jack, I think that both John and Mark have offered you some great info.

When you say "fresh water cooled", may we assume that you are referring to a "closed cooling" system? Some people use "fresh water" to describe river/lake operation.

If you do have a CCS, is yours what's called a "half" or "full" system?
(i.e, block/heads only... of block/heads + manifolds)

I'm asking due to the manifold and riser interface with one another.

If you have a "half" system, your manifolds/risers may be set up so that the manifold sea water transfer ports supply the risers.
If these transfer ports have become rust restricted, your flow may have changed and may no longer be equal....., hence the difference temperatures between Port and Stbd sides.

If you've not inspected and/or cleared these transfer ports out, it may behoove you to do so.
It'll cost you a bit of your time and a set of gaskets only.

Also (not always)... but where the spent sea water exits the heat exchanger, some use a "T" or "Y" type fitting to divert the sea water to each exhaust component.
Often these fittings do not split the water flow equally.
Several years back, one of our major Closed Cooling System manufactures had an issue with their diverter fittings.
They ended up sending out new replacements.

Some of the dual outlet heat exchangers may also pose an un-equal flow issue.


Agree.... use the IR gun, and you should be able to see a temp differential.



It's also possible that the old P-105 crankshaft pump may have contributed to the issue.
BTW.... the Johnson F6B-9 is a direct replacement/interchange, and is not as expensive as the Sherwood P-105.

.
 
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