Mercury 50hp wont turn over

[Mcadieux]

We recently bought a 2000 Macgregor 26x. The boat had been sitting in covered storage for at least the past 8 years. Today I worked on trying to get the engine to start and ran into some issues. Changed all the oil and put in a new impeller to be safe. When I try to start the boat it will not turn over. The starter will get about one revolution before freezing. If I remove all of the spark plugs the starter spins the motor. If I put the spark plugs back in and remove the lower unit the starter can spin the motor. But If both spark plugs and lower unit are on the starter can't turn the motor. I am using a brand new battery and even tried jumper cables directly to the starter. I'm figuring the starter is bad but wasn't sure what else to check before buying a new one. This is my first big outboard so not sure how it is suppose to be, but motor is very hard to turn with the emergency starting rope. Even with all my strength I can't get one long continuous pull.

[TimLa]

Just guessing: you have more than one issue. With the lower off, can you turn the shaft in the lower? The other two things that come to mind are the starter motor and/or a stuck valve.

[Mcadieux]

The drive shaft in the lower units turns easily until I put the impeller on. With the impeller in place it can be rotated but its really hard. I figured I have several issues. I bought the boat assuming the motor was a loss. It looks brand new though, still has clean grease on all the linkages etc. Motor has roughly 10 hours on it. Guy was the original owner and was like 78 when he bought it. Boat has simply sat forever.

[sailboatmike]

My Merc does something very much like you describe unless its run every 3 or 4 weeks max, even 2 large batteries wont turn the sucker much.

I have found that I give it a try and if she wont turn over leave her for a bit and top the batteries up before trying again,

Not sure what goes strange but I have 2 x 720cca batteries and you would think you are trying to turn over the Queen Mary, once freed up she spins beautifully and starts with no issues.

I have had this happen 3 times now, each time after leaving the motor a couple of months between runs.

I have now replaced my batteries just for my own peace of mind and ensure that I start the motor at a maximum of 3 weeks intervals.

I would personally have a mechanic give it a good service before trying again, and give her a spray of "Start Ya Bastard" or similar start assistor before winding her over

[1st Sail]

I would definitely replace the impeller. also look at the chamber sufrace around the impeller for corrosion and pitting.
Do a compression test of the cylinders. If possible find someone with a video probe that can inspect the cylinder walls. If the previous owner did not fog the cylinders they could have rusted which is seizing the rings. Add it all together and possibly the starter just can't turn it over.

[Bilgemaster]

I'm not personally familiar with the big Mercury engines, only those little 2-stroke fussbuckets actually made by Tohatsu. Still, I wonder if in just sitting around for about a decade those cylinder bores might have gotten a bit "crunchy" and hence "draggy" with surface rust. The piston rings might also be a bit stiff in their beds. Have you tried pulling the plugs and squirting a healthy shot of Marvel Mystery Oil or even a little Liquid Wrench into the bores, and letting it all marinate for a bit--say a few days to a week? Then, turn over the motor just a bit: squirt some more, rinse, lather, repeat. Let that capillary penetrating oil action work its magic. I've resurrected several long-idled "seized" engines on land this way, including my Amphicar's, which had sat for nearly 20 years in a shed in Poughkeepsie before I got her. To all intents and purposes she was seized and seemed deader than Caesar's cat. Runs like a top now.

The starter could be borked from inactivity, I guess, bad brush contact, a sticky solenoid or something...Though I'd first suspect the aforementioned cylinder drag to be the culprit, followed in likelihood by loose, dodgy or corroded electrical connections, depending on the storage conditions. Again, a sticky carbon brush or solenoid might ease itself back to happiness with regular use.

Sure, it may be something more dire, but from what I read, I sorta doubt it--Just a stiff old engine that needs to gently stretch her legs for a bit and be broken back in. Most likely scenario is she'll just limber herself up with use. An extra oil change or three over the next year, with a little Marvel in the crankcase (say, 1 part MMO to 4 or 5 parts standard oil [not synthetic] will gently ease out any now-fossilized crud. After a few such gentle purges, you can use the slipperier synthetic or a synthetic blend, if you like, but for now you WANT a little more friction and wear in there. A dash of SeaFoam in the fuel and crankcase couldn't hurt.

Best of luck to you. I am actually pretty optimistic that she'll square herself away just fine with a little pampering, regular use and time.

[Mcadieux]

Thanks for all the suggestions. Sprayed some mystery oil in the cylinders and turned it over a few times with the spark plugs out. Then put quite a bit in the cylinders and left the motor up for it to sit. I inspected the cylinder walls and they all looked decent. Only thing I noticed was some black around the very top of the cylinder. Pistons looked good with only some slight carbon build up. If I try to pull start it, it spins easy then takes a lot of force to get through the compression spot. I also noticed I can hear the impeller rubbing as I manually pull the motor. I'm thinking the issue is a combination of the pistons sitting to long and being tight and the new impeller being tight. If the mystery oil doesn't help I'm going to remove the lower unit and try to get it started with it off. Once I get the top free and running I can focus on the bottom end. Biggest engine I have worked on before this is a 4hp so not sure how hard it should be to turn that water pump. Glad I decided to replace the pump before I tried starting it. The impeller was actually in backwards, assuming the guy had it serviced right before it went in storage.

[Tomfoolery]

Make sure you've greased the interior of the impeller housing, so the vanes aren't running dry. A lot of cranking with no water lube isn't so great for the rubber. I'm not suggesting there is enough friction to make much difference in how it cranks - just a caution about undue premature wear.

As to the rest, it sounds like you're making the right moves so far. And I too would probably try to start the power head without the lower unit on, but obviously not run it long with no cooling water through it.

That starter motor is suspect in my mind, however. Aside from electrical anemia (check all the wiring, too), it may have mechanical rigor mortise. I'd pull it and inspect and, if the manual dictates, lube it.

[Bilgemaster]

Hmmmm....Are you SURE that impeller was in backwards before you put the new one in "the right way"--I mean, are you 100% certain that it's in there correctly now? 'Cause that might be worth taking a long and thorough 2nd look at.

[Mcadieux]

The original impeller was installed as if the drive shaft turned counter clockwise when looking from the top. I had never seen a ccw driveshaft so I checked online and couldnt find anyone with one. The manual states clockwise and I even ran the inspection camera up the foot to make sure the motor ran clockwise lol.

[K9Kampers]

The original impeller was installed as if the drive shaft turned counter clockwise when looking from the top. I had never seen a ccw driveshaft so I checked online and couldnt find anyone with one. The manual states clockwise and I even ran the inspection camera up the foot to make sure the motor ran clockwise lol.

The reference to the impeller being installed backwards is incorrect. Notice how the vanes of a new rubber floppy vane impeller are straight. When installed into the cup, the vanes become curved with the direction of the shaft rotation. The impeller cup is designed to be offcenter of the shaft, forcing the vanes at one point to compress and curve thus creating a wicking action to draw water thru the pump. The impeller draws or pulls water (not pushes) from the inflow port to the outflow port of the pump.

When the OB has been sitting for a long time, the rubber impeller takes a 'set', meaning the vanes retain their curved state. This curved 'set' reduces the ability of the impeller to function efficiently as a pump.

When replacing an old impeller, make sure that it is intact. Any pieces of missing rubber must be found within the cooling passages, otherwise they could clog and reduce or stop water flow, causing the engine to overheat.

[Mcadieux]

I have installed many impellers in smaller outboards. Hopefully I haven't always been doing it backwards lol. I just don't think i'm explaining it well. The impeller blades were bent towards the direction of rotation. Here is a picture of the original impeller.

[K9Kampers]

And so it is! I was expecting that if the engine had been run, the impeller vanes would have corrected themselves.

Rereading your previous remarks suggests that the PO had installed a new impeller (backwards) without test running the engine before storage. The dry rubber vanes pointing the wrong way is likely the cause of your issue.

Have you been able to now start (or crank) the engine with the lower unit and new impeller on and spark plugs in?

[Mcadieux]

Tried starting it up today without the lower unit on. With the motor in neutral it turns over no problem but will not start. I pushed the throttle advance button and put the throttle up. Motor starts almost instantly. I backed the throttle down to about where I think it should idle (by sound) and it runs great. If I push the throttle back into the neutral position it dies. I'm assuming their is something that is suppose to advance the throttle while in neutral that isn't currently working possibly? The bigger issue is it is leaking gas from somewhere behind the carbs. I pretty good drip is going. Thinking their could possibly be a float stuck open. I also noticed the fuel lines run behind there, but they are impossible to see.

[sailboatmike]

Could be the idle jets blocked up, if its been sitting for a while chances are the carbs are gunked up anyway, good chance to pull them down and give them a spring clean