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water pumping on 250 series

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winkles117

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I have twin 250 series engines. one blows the water out real good, the other has good water but it just flows out slowly. i know it should be blowing it out like the other and does when operating at 2000 rpm's. my question is where to start. one friend saids impeller, another saids the problem is probably rust in the exhaust manifold. like to hear what you think and where i should start.
 
More info please!
Year/model, etc. I/O or I/B?
(most likely an I/B.... but for a few years, Chrysler did use the Volvo Penta drive with the Chrysler name on it)


Your one friend who suggests impeller, may be correct......
And your other friend who suggests exhaust may also be correct.......
This leaves you with a choice of checking one or the other, or both!
Quite frankly, I'd be checking ALL areas, since cooling is so dang important.
It's not uncommon that rust scale within the Exhaust Manifold and/or within the transfer ports, will restrict outgoing "spent" sea water flow...... of which will result in limited incoming cooling water.

As with most any sea water pump and cooling systems, we need to learn and follow the sea water path.
Once the path is understood, then trouble shooting becomes easier and more effective.

Engine mounted sea water pumps require that there be ZERO suction leaks on the suction side.
One tiny breach here......., and we may loose dang near all cooling water at certain RPM.... or limited thurought the RPM range!
Any pressure leaks should be easily seen.

Also, odd as this may sound, look for crustaceans that may be in the suction side! I've removed handfuls of these before.

Check the interior of your sea water pump!
Check the two thrust areas of the interior of your sea water pump!
Check the impeller cam!

Again, follow the path, and use the P of E (process of elimination)!
You will find it! :)

.
 
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this boat is a 90 model 42' gibson houseboat on guntersville lake in alabama. these are chrysler engines and they do have the velvet drives on them and i may not have them on the right place in the forum. i just had a bottom jo done this last week so the bottom was check. so i guess i need to start with the easiest and work my way to the hardest parts to check. the engines aren't over heating, they are getting water at idle, and at running rpms they seem to blow water out good. but the best way i know to explain it is that at idle it doesn't blast the water out like the other one does, it just runs out the back of the muffler which is above the water line so you can see how much is coming out.
 
This would then use a seacock for incoming cooling water.
I mentioned Crustaceans earlier. Don't be surprised if you were to pull the hose from the seacock and find a restriction right there.

Like said, learn the path of the incoming sea water, and follow it while you eliminate one item at a time.

BTW, try to not let the "easiest" lead you away from the more "obvious"! Roll up your sleeves and get dirty.

.
 
Here's a simple test you can try:

1. Close the seacocks on BOTH engines

2. Remove the hoses from the seacocks.

3. Open them one at a time and observe the flow of water coming in.

Is the "good" engine side similar to the troublemaker?

Jeff
 
I know on my boat it doesnt blast out water, it just flows, maybe its not the flowing one that is wrong, maybe its the blasting one, just my 2 cents.
 
I like Jeff's idea. At least give that a try.
I'd make sure that the Seacocks can be opened/closed easily before you get too deep into this.
Have a back-up plan in case one handle would not close off the valve.

I had a new thought.
Is there a chance that one sea water pump has been replaced, and possibly replaced with a larger capacity pump??????
 
not sure. that is a thought. i know on my old 318 it would blow water out like the one good one does now. but in saying that theone that blows good, i was told the engine was rebuilt so that could be a good possibly. i think your right, start at the sea cock and work my through
 
I agree with all mentioned above. Go through the troubleshooting suggestions for the raw water supply. If all checks out good, a dislodged baffle in a muffler will change the discharge pattern. Which was the normal flow for this vessel, smooth flow or shooting out?
 
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