Did I break it?

[dirtrybird]

I recently bought Mercury 7.5 HP outboard (between 1974-1976) from a guy who said he last ran it 2 summers ago. I got it home, sprayed some starting fluid in the carb and it fired up!

I noticed it wasn't pumping water but had to run inside for an emergency. About 10 minutes later I came out and it had shut off and, needless to say, was VERY hot.

I didn't try starting it again until I installed a new impeller and also some new plugs. I also sprayed the carb with carb cleaner from the local auto store. I tried to start it after all that but it won't stay running. When I spray it with starter fluid it runs for about 5 seconds and then stalls out. So far I:

- checked the fuel line to the carb and it's getting gas
- took apart the carb and cleaned it
- gapped the plug at .40
- cleaned the relays

Not sure what else to do at this point? It was running fine for that 10 minutes until it shut off. I think it's getting a spark since it runs for a few seconds but don't think it's getting gas. If anybody has any ideas what to try next PLEASE let me know! Fishing season is here and I really want to hit the water!

 

[will941s]

Re: Did I break it?

When you ran inside and came back out, and the motor had shut off....it ran hot. Which means that the internal parts expanded and stuck, causing the motor to grind to a screaching halt internally. Get a compression tester and do a compression test. Hopefully the overheat did'nt score the clyinders and break some rings/ destroy the pistons. Take the plugs out, tilt the motor up and pour some outboard oil in the the cylinders. Turn it a few times then do the test. If it checks out then you might be ok. NEVER use starting fluid to start a OB, use a gas oil mixture. When you do, you pretty much cleaned the oil off the parts in the motor and started it dry. Then it had to re-lube it's self, but it's that time between where it ran dry that causes the damage. If the compression is bad....well, either rebuild or get another motor.

 

[dirtrybird]

Re: Did I break it?

Thanks, I'll give it a shot! Quick question...how much oil should I pour into the cylinders?

 

[will941s]

Re: Did I break it?

Just enough to coat the cylinders and get down to the rings. If it's mounted on a boat, you may want to put the oil in the spray bottle and spray it in there. Spray it, rotate the fly wheel, spray, rotate, spray....look in there to make sure it's coated. Let it sit for a day or so. Also spray some through the carb into the engine while your rotating the flywheel too. To coat the crank and the bearings. You can take the plugs out, rotate the pistons to the top and look at the top of the pistons for pitting or damage, then rotate them down and take a look at the cylinders with a small flashlight for scoring and metal transfer. If you want to be more investigative, you can take the exhuast cover off the side of the motor and look at the rings on the pistons if all else fails. They should be flat, squared and fit into the grooves, not flattened out or broken. If you do take the exhuast cover off, make sure you can get the gasket set and be prepared to remove broken bolts. Seems scary but try the oil and the compression test first, that will let you know what you need to look into, if anything.

 

[dirtrybird]

Re: Did I break it?

Just wanted to let you know that I tried what you suggested below and it worked! The engine is running like a charm. Thank you VERY much!!!

 

[j_martin]

Re: Did I break it?

Don't forget to DISCARD the starting fluid.

 

[dirtrybird]

Re: Did I break it?

I definitely will! I just ran into another problem though...I put it in neutral to start it but when it fires up it's in gear. I put it in reverse and it acts as neutral. There's no difference between neutral and forward when it's running. When it's not running it won't start unless it's in neutral. Any ideas?

 

[dirtrybird]

Re: Did I break it?

Okay, from what I read this happened when I changed the impeller. I'm going to remove the lower unit. My question is: does the engine need to be in reverse when I put it back together?

 

[dirtrybird]

Re: Did I break it?

Everything is fixed and running like a charm!