Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

[Frank O]

This morning we went down to take out my 21-foot center console for the first time in five weeks. The 1994 Merc Offshore 3.0L 225HP carbureted 2-stroke engine started normally. Just after we pulled out of the slip, the engine died. At this point it had run for a total of about 1 minute. After this the starter motor would crank, but the engine wouldn't start up.

While looking things over, I noticed one important point. The last time we used the boat five weeks ago, I got interrupted when I was running freshwater through the engine at the end of the day, and I forgot to reinstall the plug on the fitting in the bottom cowl where the garden hose is attached during flushing (I don't use muffs, but instead connect the hose to the back of the engine). I found the plug in my toolkit and screwed it in. After this, however, the engine still wouldn't start.

I'll be going back down to the boat in a few days to work on diagnosing this. In preparation, I wanted to ask the following:

1) Would the lack of water pressure due to the plug in the cooling system not being installed cause the engine to shut itself down?

2) If so, what could account for the fact that the engine wouldn't start after the plug was replaced? Could several attempts to restart it have caused the engine to flood?

The gas tank incidentally is about half-full, and I verified that the bulb in the fuel line stiffened normally and was putting out clean gas. There is also plenty of 2-stroke oil in the outboard's reservoir. No alarms (such as overheating alarm) sounded while running or trying to restart the engine. Thanks for any ideas.

 

[Kev144]

Re: Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

Your saying you ran it with out water at all? It is possible with no cooling at all you could have seized it up from heat. I would see if you can turn the flywheel manually by hand first to be sure it isnt seized solid.

 

[hkeiner]

Re: Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

I don't know how the "plug scenario" could cause the motor to crank but not start. Even if one speculates on what could have happened, you still would need to determine/confirm what is wrong. I would suggest that you go ahead and do some basic troubleshooting. First, confirm whether there is a good spark on all cylinders when cranking the motor. If the spark has failed, you can then troubleshoot that further. Second, spray some 50:1 (fuelil) mix while cranking the motor to see if it responds. If it does, you can troubleshoot that further. Narrowing down the problem between failed ignition or failed fuel delivery is where I usually begin when my motor does not want to start.

 

[gss036]

Re: Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

I agree with hkeiner on his resoluition. There is no reason for it not to run w/ the cap off. The water pump would just pump water out through the hose bib and less water to the engine cooling system.
Check to make sure you have fuel and spark

 

[Frank O]

Re: Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

Thanks for the suggestions.

Kev144, I suppose seizing up is always possible, but wouldn't the overheating alarm have gone off before this point?

Hkeiner, being relatively new to outboards I have to ask -- to check for spark would I just take the upper cowling off, pull one of the spark plug wires at a time, crank the engine and observe if there's a spark? On my old VW we do this holding the spark plug wire close to a grounded part of the engine, but I guess the more modern way to do it is with a spark tester. Would you recommend the latter?

Also, when you say "spray some 50:1 (fuelil) mix while cranking the motor to see if it responds," spray where? Into one or all of the carbs?

 

[hkeiner]

Re: Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

To check for spark would I just take the upper cowling off, pull one of the spark plug wires at a time, crank the engine and observe if there's a spark? On my old VW we do this holding the spark plug wire close to a grounded part of the engine, but I guess the more modern way to do it is with a spark tester. Would you recommend the latter?

I would use a spark tester, which can be obtained at any auto parts store. There is the "in-line" type with a fixed gap, which connects between the spark plug boot and the spark plug. There is also an "adjustable" type where you can adjust the gap. One end connects to the spark plug boot and the other end has a clip for attaching to ground. Either style would be OK for your purposes. In a pinch, you could even use an inductive timing light, if you have one, to test for spark. You would test one spark plug at a time.

I would not suggest that you merely hold the spark plug wire near ground to check for spark. While I do not know this from my own experience, I understand that if you run the motor without grounding the spark plug wires, you risk damage to the ignition system. This may not not be true, but it is not worth the risk in my mind.

Also, when you say "spray some 50:1 (fuelil) mix while cranking the motor to see if it responds," spray where? Into one or all of the carbs?

You would take the plastic cover off from the front of the carbs and spray into the throttle body throat. You need only spray into one carb at a time while cranking.

 

[Ed R]

Re: Will loss of water pressure shut down '94 Merc 225HP 2-stroke?

er back on line, the flush plug should be put back, how ever, there is a check valve behind plug that would keep water in power head . not starting has nothing to do with it .Check kill switch , primer bulb, [make sure its hard, and battery voltage, is motor cranking over fast enough?