How much engine damage did I do?
 

I think this is really bad but not sure. Decided to replace the impeller in water pump before spalshed today. Genius me didn't realize the pump fits in the bracket two ways, I put it in upside down so hoses are connected backwards. Put boat in water and started to run around to slip. After about a minute notice temp shooting uo and temp alarm sounds. Got up to about 220-2430 deg. Shut down and pushed around into slip.

Wnet in and flipped the pump around and go to restart and is locked up. Mechanic helps me pull plugs and water comes out of all four front cylinders. Back four are dry. Now it will crank though. So we turn it over and push all the wwater out of the cylinders. He fogs all cylinders real well and replaces plugs. Cranks fine but now won't start.

It is a '88 Merc 7.4L w/ Bravo I drive. Questions are where did the water come from if the pump was pushing water out? and how much damage did I do. Engine was only two years old. Mechanic is looking at it tomorrow to see if can get to start. What is the next best step?

Thanks

Blown head gaskets. Remove, resurface, and replace the heads.

Unless your temp estimation is not a typo and you actually got it to 2430 degrees then everything is toast! :rolleyes:

Good luck!

Ron

If the boat had water in the block, then it still had water in the block, being circulated around by the circ pump on the front of the motor. Your raw pump puts water into the motor at the tstat housing, so it just kept sucking air from the tstat housing - didn't have any way to suck your block dry - can only do that by opening the petcocks.

Your impeller will more likely than not be toast. Plan on replacing it.

Ron is right about your headgaskets, although your overtemp horn should have sounded before you lost your headgaskets. If you got water in it, though, it's gonna be headgaskets. Run a quick compression check and it will tell the tale.

You may want to plan on replacing the rubber exhaust hose also if it ran dry that long.

It's not gonna be horrid. Headgaskets aren't too expensive.

Ron when you say replace the heads do you just mean put back after resurfacing or do you mean put new heads on?

What should the correct compression be for this engine?

The mechanic wanted to try to start tomorrow. If it does start, or just by cranking it, I am concerned that now that the pump is flowing correctly and assuming the headgaskets are blown it will suck in alot more water and do much more damage. Is continuing to try to start it a bad idea? There was no water in the oil. Also why would only the front cylinders have water in them and the back dry?

Which hose is the rubber exhaust hose you are referring to?

Thanks guys. The s$%^ never ends.

did you winterize? perhaps water was there from cracked block ! ive seen motors over heat alot and seldom do the eat head gaskets.

later

Your impeller is already junk.

I say dry start it all you want, just don't dry start it with a new impeller or it will be junk too.

Don't worry about what the compression should be, just look for consistency cylinder to cylinder.

Why the fronts? Dunno. Why not.

Rubber hose from manifolds to the exhaust tips.

Possibly cracked the heads, thats where I suspect the water is coming from. Also, check the piston tops for smiles from the exhaust valve striking them. No water circulating through the heads causes the valve guide to seize the exhaust valve.... the piston inevitably strikes it.
If the heads have to come off...have them magna fluxed and checked to see if they are warped.

My buddy just did the same thing on a used crownline. Bought it, never checked the impeller, after 15 minutes in the water it overheated. Shut it off, let it cool, wouldn't crank (actually broke the starter trying). Ended up being a cracked cylinder. Had to pull the engine and get it sleeved. They said his heads and gaskets were fine.

I think 230 would not have been enough to blow a head gasket . But I have never ran one out of water. On one of my race care I lost a fan belt once and it went to 260. and did not hurt anything. just changed the oil:eek: .Still had water in it though.

I would not try to crank it up ..if water gets in there you'll be bending rods.

Rob

It is also very likely that your temps were MUCH higher as your block was full of air your temp guage was probably not reading properly.

I would do a compresion check first, then if it looks good try and start, if not then stop and find out why. If you can get it to start quick then shut it down and put a new water pump on it. Run it for a bit then pull the plugs and check them.

Jon