Cooling System

[yasky]

I have a 1988 Formula, with a 454, low water pickup. I took the boat on the water for the first time yesterday. It seemed as if there was no water getting into the engine, and naturally it overheated. I took the boat out and brought it back home, where I then ran water through the engine and came out fine. So I don't think there is anything obstructions in the lines. From the water inlet and before the water goes into the motor there is a strainer. When I opened this I did find some plastic pieces and cleaned it out. Again ran water completly through the entire cooling system. Can anyone explain to me the theory behind the low water pickup and maybe have any advice as what to look for or even test?
thanks for your help

[Suede]

Hi...
this one seems to be perfect for Gonzo ;-)....but have you checked the impeller (water pump with a rubber wheel in boating)...sounds like the pieces might be from the pump....and it´s a cheap fix...

Regards
Olle

[gonzo]

If you can run water through the water system, the impeller is bad. Check the raw water pump. If it broke, also check the power steering cooler and other heat exchangers you may have for pieces of impeller. Even though they may not cause a problem now, they may in the future.

[ColinZ]

With our 350 Chev, whenever we want to run the engine when the boat is out of water, I disconnect the water pipe from the entry side of the water pump and attach a small flexible pipe to the pump. The other end is put into a large bucket (about 10 litres) and the bucket is filled with water.

As the engine starts, water should be sucked out of the bucket by the pump, thus indicating that the water pump is working. Keep filling the bucket as it the level decreases for the duration of your engine run. Remember, when you attach a water hose to the input side of the water pump, the water is coming out under pressure so you are not actually checking to see if the water pump is working

[zr1_lt5]

i have the same problem with my 1985 omc renken, and i replaced the impeller and rebuilt the raw water pump. the boat ran fine and cooled properly for the first run, but now keeps overheating. i have taken the impeller out and it is ok, and i have followed the water flow into the engine, and it is getting plenty of water. but it still keeps overheating, this only happens when it is in the water not when i have a hose hooked up to it. also i read somewhere that the water should be coming out at the prop. but it is not. any help?

[gonzo]

Do you mean it oveheats in the water at idle or under power?

[zr1_lt5]

mostly at idle, but sometimes it does overheat under power (mostly under 1700 rpm)

[gonzo]

Have you checked the risers. The engine will overheat if they are clogged.

[zr1_lt5]

thats the first thing i was going to check tomorrow morning...just figured i would get a second opinion before i did some useless work

[andy400ex]

i recently put a engine in my boat (chevy 4.3 v6) it has a brand new water pump seems to be pumping plenty of water exhaust does not get hot when the engine is running water temp comes up a little when running when it gets warm i can feel and hear the water boiling in the hose off the water pump i have pulled the hose to confirm dont know what else it could be if anyone has an answer please let me know thanks andy400ex

[Poida]

Just a thought.

In my boat the water is pumped through the engine, gearbox and manifold.
When you check your cooling system with the hose, you may be seeing the water coming from the gearbox and manifold, there may be none coming from the engine.

Andy it would seem strange that if your pump is pumping plenty of water the water off the pump would be boiling, I am assuming you are pumping sea water. It may not be boiling water you can feel or hear, if the pump is too large it may not be getting a good supply of water and the sound and bribrations you are feeling could be cavitation.

[StianM]

Originally Posted by Poida

Just a thought.
Andy it would seem strange that if your pump is pumping plenty of water the water off the pump would be boiling, I am assuming you are pumping sea water. It may not be boiling water you can feel or hear, if the pump is too large it may not be getting a good supply of water and the sound and bribrations you are feeling could be cavitation.

Well he say this hapend when the engine is warm so I wonder what pump he is talking about. Is it seawater cooling pump or is it engine circulation pump?
Is it centrifugal or displaisemt pump?

Cavitation sound more like gravel flowing in the water then boiling acording to my exsperience.
So what is the sound like?

[gonzo]

What do you mean by boiling off? If the temperature gage is showing normal temperature then the engine is at is operating point. The raw water pump can't boil off because it is picking up cold water and sending it to the engine.

[StianM]

Originally Posted by gonzo

What do you mean by boiling off? If the temperature gage is showing normal temperature then the engine is at is operating point. The raw water pump can't boil off because it is picking up cold water and sending it to the engine.

The only way that could hapend is if the waterpump is sucking the water trough the heatexstanger. Then it would make sence.
When the pump create vacum the boiling point off water will drop and when the engine get hot the water flowing trought the heatexstanger could reatch a point where it will boil, but I so far only see pumps with the heatexstanger on the preshure side and not on the suction side.

Could we have a bether discription off how the system is working?