How to rotate mercruiser 3.0 manually

[9533Zero]

New to the board... Not new to boats. I'm trying to bring a 1987 Mercruiser 3.0 back to life. It hasn't run in at least two years and the engine did have water in it. Not sure how bad it is. I want to remove the plugs and rotate the engine manually but don't see an easy way to do it. Do I have to remove the outdrive and rotate it from that end? Is there a better way? Thanks!

 

[Don S]

Re: How to rotate mercruiser 3.0 manually

Make sure the alternator belt is tight and use a socket on the alternator. WIth the plugs out, the engine should turn easily.

 

[chiefalen]

Re: How to rotate mercruiser 3.0 manually

If it don't turn easy, than pull the plugs. Shoot pb blaster in the plug holes.Than try turning it Don s way.

Still don't turn, pull the drive, may be frozen not letting the motor turn.

Still don't turn pull the valve cover off, or you can pull it off when you pull the plugs. Shoot pb blaster all over the rockers valves everything.

Still don't turn post. we will go from there.

Welcome aboard.

 

[alumi numb]

Re: How to rotate mercruiser 3.0 manually

first, i don't know about yours but this is what i did on mine "120".
projecthog gave advise that was helpfull to me.
i way over filled the crankcase so the crank is under thin oil.
use what you want trans fluid whatever, i use/used 30/70% diesel fuel/oil.
i pulled the valve cover and shot a generous amount of blaster using the straw onto the valve stems and all over.
then pulled the plugs and really laid into it with the blaster.
in short oil the heck out of everything you see other than the belts.
i even sprayed the hose clamps, bolts, carb and linkage, starter, everything.
then on the right side of the engine just above the starter there is about a 1" opening.
you can see the teeth on the flywheel and this is were i used a large screwdriver to pry against the teeth.
be very careful and just try to work the flywheel back and forth lightly.
i cut several small pieces of wood to pry against so the screwdriver wasn't resting on metal.
it took me an easy hour or more of just working the teeth back and forth "easily".
at first it looked like i was getting nothing.
then it looked like i was getting something but it was so little i wasn't sure if i was getting anything at all.
finally i got a little more and a little more untill i could get a full revolution.
from that point as don s mentioned i could use the alternator.
well good luck and hope it works for you as it did for me.
to all thank you for your help.

 

[Don S]

Re: How to rotate mercruiser 3.0 manually

Kind of jumping the gun with unsticking a stuck engine when he just ask how to turn it over by hand. No since going to all that till he tries to trun it over. It may be fine.

 

[alumi numb]

Re: How to rotate mercruiser 3.0 manually

don s, can't think of any time in life that i ever got to much information.
can think of plenty of time i got not enough or the wrong info.
but your right and in a way violated my own code.
i'm all ears.

 

[Don S]

Re: How to rotate mercruiser 3.0 manually

I'm just suggesting it's not time to start treating the engine as though it's locked up until we get some feedback from 9533zero. We could bury him in useless information if none of the information actually applies to him, and it makes it worse if he doesn't know if it applies or not.

 

[alumi numb]

Re: How to rotate mercruiser 3.0 manually

i like iboats.
now back on track,thanks.

 

[9533Zero]

Re: How to rotate mercruiser 3.0 manually

WOW! Thanks guys! And don't worry, I'm a firm believer in having more info instead of less. Actually, you guys were right on track. I'm sure the engine is locked and was just beginning to think about the processes ya'll described. I'll be back at it later today and will give the board an update.

BTW, I removed the carb and it was pretty bad. More water in it than fuel. I think I can salvage it though and will do a rebuild on the card and continue the process of trying to free/evaluate the motor.

Oh yeah, I LOVE working on old rusty junk! Its fun!

Steve

 

[9533Zero]

Re: How to rotate mercruiser 3.0 manually

Well she's free, almost anyway. Followed all the advice above and got it moving. I can rotate it with the alternator nut. Now the bad news, its binds up before a complete rotation. I think there is some rust at the top of one of the cylinders. I think I'm going to have to pull the head and manifold to inspect everything. I also pulled the valve cover. It didn't look too bad but there was some minor rust on top of the rocker arms, more like staining than rust. At this point, I have gunked everything down with PB Blaster and taking things one step at a time. Probably looking at a complete rebuild, but that's ok. I can handle it.

One thing I can't figure out is where all the water came from. There was water in the carb and intake manifold and obviously under the valve cover. There is no evidence the boat was ever submerged and I don't know how water could have gotten that high. Any ideas? Thanks guys!

Steve

 

[Don S]

Re: How to rotate mercruiser 3.0 manually

I think there is some rust at the top of one of the cylinders.

Well, you can use the pistons, rings, and the rust as a grinder and start it up till it wears itself in, but that usually brings a short life to the engine.
Best bet. Pull the engine disassemble, and inspect. Install new parts to replace bad, and bore it out if necessary.

 

[chiefalen]

Re: How to rotate mercruiser 3.0 manually

You know for sure it was never submerged?

Than maybe someone left the plug in and water just went down the carb.

Someone left it uncovered? The motor?

Did you taste the water is it salt water?

One last thing i sorta knew already you would have to take down the motor.

Water even fresh left in the cylinders for more than a few days would start to rust it.

Check the manifold and riser real good maybe you had water come in cause of those.

Head when you take it off, take off the t-stat housing completely off.

Look in the hole, what do you see?

Good luck let us know how to made out.

 

[9533Zero]

Re: How to rotate mercruiser 3.0 manually

Don S., Chiefalen,... Thanks again for your advice. I'm going to be cracking on this motor as for the rest of the winter and will post updates to the board as I have them. Well, tim to go pull the head! cheers!

Steve

 

[abj87]

Re: How to rotate mercruiser 3.0 manually

Is it a freshwater boat? I'm sure someone will disagree with me but 20 years of salt water use will pretty much destroy the block and make it not worth rebuilding.

 

[9533Zero]

Re: How to rotate mercruiser 3.0 manually

Left a couple of guys off my Thank You list so thanks to all.

Fresh water boat. I pulled the head and have one rusted cylinder. Its soaking in blaster right nbow and not sure how bad it is. I'm gonna have the head reworked and will keep evaluating the block.

Steve

 

[chiefalen]

Re: How to rotate mercruiser 3.0 manually

Steve where you located?

Soaking it is the first step.

But no way to know what everything else looks like till you turn it over and pull the pan.

Sorry to tell you that.

But fresh water might just save you.

When you pulled the head whats the riser look like and the manifold?

 

[9533Zero]

Re: How to rotate mercruiser 3.0 manually

I'm in Gulf Breeze, FL, near Pensacola.

As for the riser, I haven't looked at it yet. The manifold looks great on the exhaust side but there was water in the intake side. I'e started to clean it up and it doesn't seem too bad. I think its very salvageable. I will probably send the head to a loca machine shop to be reconditioned.

BTW, I spoke to the former owner and he doesn't think it could have ever been submerged. Only thing he can think of is that his kids may have removed the engine cover and left it open. He also said the boat has never been farther north than Pensacola so freezing/cracked block may not be a problem.

Thanks Chief!