Logo
FULL SITE MENU

Crusader 6.0 overheating

B

bdaalex

New member
Hi.... at a total loss on my engines and my mechanic has given up. I have 2015 Crusader 6.0 engines in my Tiara 3100 open, not the catalytic ones, traditional exhuast. About 18 months ago, the port engine overheated and blew the head gasket. Since then, no matter what we do, it runs hot and overheats at planing speeds. At 5 knots its fine, at 10 its hot, at plane it overheats. We have replaced the heat echanger, the exhaust elbows, the head gaskets twice, checked the fresh water and raw water pumps, checked the intake, checked pretty much everything we could think of. We have re-bled the coolant several times and flushed the fresh water loop many times. We have run it with and without thermostats.

As I said, my mechanic has given up and we have no idea what else to check. My thought has always been that the saltwater must not be flowing fast enough to transfer the heat out of the heat exchanger, but there is no indication that is the case and I'm not a mechanic so what do I know.

anyone have any ideas?
 
Does the coolant over flow bottle fill up or drain out?

Get a clear length of hose and barbed fittings from hardware store. Cut short pieces and place them inline where raw water goes into the heat exchanger (HE). Place another where raw water exits HE going into exhaust. Your looking for bubbles
 
I will try that, thanks. i figure its either air getting in or restricted flow on the raw water but wasnt sure how to check. makes sense!
 
my other idea is to get a smaller pulley for my raw water pump to increase flow a bit but i have no idea where to find one that would fit.
 
bdaalex said:
no bubbles there. that was corrected with new head gaskets.
Click to expand...
Wondered when it starts overheating does the level of coolant in the bottle change up/down?

bdaalex said:
my other idea is to get a smaller pulley for my raw water pump to increase flow a bit but i have no idea where to find one that would fit.
Click to expand...
Don't see that as the issue because the other motor has no issues.

Another thought is if the exhaust is restricted which in turn would reduce the amount of flow going thru HE.
 
I can check the level of coolant. i assume you are thinking air lock but we have re bled it so many times i dont know how that could still be possible.

we replaced the exhaust elbows so they are brand new and definitely not restricted.
 
bdaalex said:
I can check the level of coolant. i assume you are thinking air lock but we have re bled it so many times i dont know how that could still be possible.

we replaced the exhaust elbows so they are brand new and definitely not restricted.
Click to expand...
If level goes up than might still be getting compression gases into the coolant. If it goes down than there is an air pocket. Just trying to understand what is happening

Most the motors have mufflers after the exhaust elbows which can collapse internally, but if yours is straight hose than that should not be an issue
 
funny, i thought it went up if their was an air pocket because the air bubble would expand when it heated.

I actaully dont know if the boat has mufflers installed. if it does they are buried deep in the corner of the engine room. i will check! wouldnt a collapsed muffler cause other issues like reduced performance?
 
i think thats less likely then. it gets up to RPM fine, it just overheats once its there.

but at this point anything is possible so i will check. in researching further i guess the hoses can delaminate and collapse internally too. i will check that.
 
no bubbles at idle and then so many bubbles when I increase throttle. Looks carbonated.

I’m going to remove the raw water line from the seacock and put a garden hose in it. Pressurized water will hopefully spray out from somewhere before the raw water pump.

Thoughts?
 
bdaalex said:
no bubbles at idle and then so many bubbles when I increase throttle. Looks carbonated.

I’m going to remove the raw water line from the seacock and put a garden hose in it. Pressurized water will hopefully spray out from somewhere before the raw water pump.

Thoughts?
Click to expand...
I would look real close at your raw water pump. Could be the pump or hose connections has a leak or the inside of the pump or impeller is worn/grooved
 
Forgive my ignorance here but how could worn or grooved do this? Loose hose I get but a worn or grooved pump should not let air in? Unless it’s cavitation? That seems intense for a water pump.
 
Take a glass of water put a table knife in glass and stir, the knife creates a low pressure surface on the opposite side of the blade pushing against the water. That low pressure area creates bubbles. Same thing happens with a prop going thru the water at even low speeds

So if there are grooves in pump housing or impeller is damaged similar thing can happen, not as great as a air leak but needs to be investigated
 
Ok. I think my plan is to move the clear hose to the intake of the pump. Then I will know if it’s the pump. Then I will move to strainer outlet. Narrow down my search. Unfortunately the oil cooler is on a nearly impossible part to reach so hopefully it’s not there.

You have been super helpful, Thankyou. Will let you know what I find.
 
Moving to the intake side can cause another problem. The clear hose is most likely not rated for suction, so the hose can collapse and cause overheating
 
make sure the strainer's cap gasket is in good condition and the cap is tight too...it can be an air source that can be a major PITA to find...
 
Well, no luck. I removed the suction line from the pump and connected a hose, closed the seacock and pressurized. There was a small drip from the oil cooler which tightening the hose clamp fixed. No change to bubbles. I inspected and lunricated the raw water pump. No change. I swapped the water pumps with my good engine, no change on either motor. I also removed the cap to the strainer and replaced with lubricant around the seal.

There is still air in the line.

Someone suggested running a hose from the seacock to the pump and bypassing everything in between just to confirm bubbles disappear. The other thought I had was to cross the lines from engine to engine right before the heat exchanger. My good engine will feed the heat exchanger on my bad engine and vice versa.

One other thing, the coolant did rise in the bad engine. Not dramatically but it did. It also has bubbles on the surface but no bubbles entering. The bubbles are more like soap suds and I’m wondering if it’s from whatever my mechanic used to flush the fresh water side. I took some out of the engine and much like soapy water it gets suddsy when you shake it.
 
If you are thinking flow, see if you can get a bucket under the exhaust outlet and measure how much water comes out in a certain period of time and compare it to the other side.

Restriction in the engine oil or gear (transmission) oil cooler?
 
Back
Top