Logo
FULL SITE MENU

4.3 mercruiser engine barely cranks over.

M

mercuryguy

New member
[h=2]1997 4.3 Mercruiser engine barely cranks over.[/h][COLOR=#6A6A6A !important]Yesterday, 08:36 PM

[/COLOR]

My 1997 Stingray with a 4.3 Mercruiser will barely crank over now. Was running and cranking fine and all of a sudden the engine will barely turn over. This occured after a 30 minute wide open throttle ride. The engine all of a sudden started slowing down and finally stopped. It will barely crank over one revolution and then stop with a known good battery and even a 200 crank assist battery charger even with the sparks plugs REMOVED. Removed the starter and it bench tests good (ie. it will spin freely when connected to a battery, i spun it over 10 times or so at least). The teeth on the starter and flywheel look fine and the bendix gear snaps back and forth fine. There is no clicking sound coming from the solenoid like a dead battery would indicate. Does anyone know what size the crankshaft pulley nut is? I need to turn the engine over by hand.
 
mercuryguy said:

Does anyone know what size the crankshaft pulley nut is? I need to turn the engine over by hand.
Click to expand...

DO NOT use the center crankshaft bolt for this!
(Unless you are willing to pull the crankshaft and take it to a machine shop for bolt fragment extraction!)



.

 
Last edited:
While conferring with engineers from two different OEM engine manufacturers some years ago,I was told that running at Wide Open Throttle results in drastically reduced ( in some cases, 10s of hours) engine life. Some posters on this forum disagree with me. Then again the guys who race boats and cars often tear down their engines "frequently". Personally, I keep continuous operating RPMs at 80% or below maximum observed Wide Open Throttle RPM ( providing this RPM is within the engine's specifed WOT RPM range) and only run at maximum for a few seconds a couple times a year as an "engine health check".
 
God forbid don't ever turn engine over using center crankshaft bolt, even though it's been done for years. For some reason people here think you're stupid enough to brake bolt off, I've never seen before.
 
Like mcm said eliminate lower unit.
Dockside do u work on outboards if so , you have special crankshaft turning tool for all engines? If so(working on outboards) how do you justify removing flywheel and installing your special tool to tell customer motor is locked up? What do u charge $$$ wise, 1 hr.? If u pull all spark plugs motor should turn easily. Or is that a way to get that 1 hr. labor charge.. OP said motor turns over slow, so not locked up, may be on its way to being locked up. If he has a galling piston.
 
Start with Post 4.
Remove lower drain screw and see what gearlube looks like.
Is silvsr the you most likely have a drive issue.

Remove outdrive from boat. Retry to crank over.
If it still wont crank with known good battery and spark plugs (all) removed then you most likely toasted the engine.

No need to try to turn over by hand...wont change results.
 
Mikey N.C. said:
Like mcm said eliminate lower unit.
Dockside do u work on outboards if so , you have special crankshaft turning tool for all engines? If so(working on outboards) how do you justify removing flywheel and installing your special tool to tell customer motor is locked up? What do u charge $$$ wise, 1 hr.? If u pull all spark plugs motor should turn easily. Or is that a way to get that 1 hr. labor charge.. OP said motor turns over slow, so not locked up, may be on its way to being locked up. If he has a galling piston.
Click to expand...

WTF are you talking about?

Unlike most marine mechanics, I do not charge for diagnostic time, since it would only take me a few minutes to figure out what is wrong with this engine.
 
Your answer is in here. You beat it to death

"My 1997 Stingray with a 4.3 Mercruiser will barely crank over now. Was running and cranking fine and all of a sudden the engine will barely turn over. This occured after a 30 minute wide open throttle ride. The engine all of a sudden started slowing down and finally stopped. It will barely crank over one revolution and then stop with a known good battery and even a 200 crank assist battery charger even with the sparks plugs REMOVED"

It could be a seized drive but knowing the V6 my moneys in a trashed motor

 
Docksidemarineservices said:
Mickey NC said:
If he drops lower unit , and motor doesn't turn, bingo
Click to expand...
How about pull the whole drive.
Click to expand...

Ditto Chris, and how about ......... "Engine" doesn't turn, bingo!
( this is Marine Engines dot com....... not Marine Motors dot com! ) :D

**********************************

Mikey N.C. said:
God forbid don't ever turn engine over using center crankshaft bolt, even though it's been done for years. For some reason people here think you're stupid enough to brake bolt off, I've never seen before.
Click to expand...
RicardoMarine said:
Did you happen to read post #1?
Click to expand...
Mikey N.C. said:
Then he more than likely gallded a piston
Click to expand...

Possibly, and possibly more than one!
If so, would you still recommend using the center crankshaft bolt to turn the engine over?

The torque for this bolt is approx 60 to 70 foot pounds.
If it was to require 90, 100 or more foot pounds of torque to rotate the seized engine (with this bolt), what are the chances of this bolt breaking?
And if it did break, how easily could a person extract the fragment while the engine is still in the boat?
Is it worth the risk, or would you be better off using the correct tool or a strap wrench?




.

 
Last edited:
..."This occurred after a 30 minute wide open throttle ride. "

Did you think that was an electric motor! I can't believe people do that to an engine.

Jeff
 
"This occurred after a 30 minute wide open throttle ride. "
Click to expand...

fastjeff said:
Did you think that was an electric motor! I can't believe people do that to an engine.

Jeff
Click to expand...

Jeff, I can't agree with you more.

We have another member here who thinks that running @ WOT RPM for long duration is OK.


WOT RPM cartoon.jpg
 
If the engine seized at WOT it's probably due to something not being right. Restricted oil pickup, maybe a worn out oil pump, something like that. A marine engine can't ever get to a point that it's "tearing itself apart" like in some kinda engine-blow contest. At some point it runs out of ability to push the boat uphill any faster as the horsepower runs out. You get to a balance of RPM, speed, and HP where it just won't go any faster. Is this outside the ability of the engine to keep itself cool and lubricated? No way. These things have been tested at WOT for many thousands of hours by Mercruiser themselves. They know their consumers will do this (floor it), and there's no way they would be eating the cost for a bunch of seized engines if this were actually the case. I mean really. If it says it goes to ten, then let's got to ten!
A balanced engine, even the lowly chevy v6, should be fine even at 10K rpm. The issue is stuff like valve float that keeps the revs down to 7K. A boat will struggle to get over 5-6 at WOT, so it's well inside the performance envelope.
Y'all think what you want but I'm with Jack. Run the bejeezus out of it.
As to the OP's problem, hope its nothing serious.
 
o2batsea said:
If the engine seized at WOT it's probably due to something not being right. Restricted oil pickup, maybe a worn out oil pump, something like that. A marine engine can't ever get to a point that it's "tearing itself apart" like in some kinda engine-blow contest. At some point it runs out of ability to push the boat uphill any faster as the horsepower runs out. You get to a balance of RPM, speed, and HP where it just won't go any faster. Is this outside the ability of the engine to keep itself cool and lubricated? No way. These things have been tested at WOT for many thousands of hours by Mercruiser themselves. They know their consumers will do this (floor it), and there's no way they would be eating the cost for a bunch of seized engines if this were actually the case. I mean really. If it says it goes to ten, then let's got to ten!
A balanced engine, even the lowly chevy v6, should be fine even at 10K rpm. The issue is stuff like valve float that keeps the revs down to 7K. A boat will struggle to get over 5-6 at WOT, so it's well inside the performance envelope.
Y'all think what you want but I'm with Jack. Run the bejeezus out of it.
As to the OP's problem, hope its nothing serious.
Click to expand...
Exactly.
 
Hey guys. Thank those of you who had some sincere input. I got the engine to turn over via the crankshaft/harmonic balancer, but with much effort with the plugs out and the serpentine belt off. So, I think I probably have an internal engine problem. Those of you who just saw fit to make some sort of child's BS remarks, you should actually sit back and really take a look at what you posted. These forums are intended to assist and give HELPFUL advice. Just because you have posted hundred's and even thousand's of times does not mean you are a expert at anything. The moderators should take a closer look at the posts and deal with members who just make posts to add to their profiles.
 
For someone with 5 posts and a broken boat you sure have a strong opinion, maybe focus that energy on your broken boat.

Every one has opinuons just like you know what

And for what is worth now....... if the starter wont turn it over with no spark plugs/no compression there is no point in doing by hand.
At that stage pull the engine and then figure out your issue.
 
Last edited:
Dear OP, this is a free and open forum. Sometimes you get what you want and sometimes your thread gets hijacked and turned into a big fur ball. Have a beer and chill. You're being a d^^k at the moment. I'm sure that's not the impression you want to give on your first post.

mercuryguy said:
Hey guys. Thank you for your input. I got the engine to turn over via the crankshaft/harmonic balancer, but with much effort with the plugs out and the serpentine belt off. So, I think I probably have an internal engine problem. I'll look into it further and post my findings. Maybe you'll have some ideas after I have more information.
Click to expand...

Fixed it for you
 
Last edited:
mercuryguy said:
Hey guys. Thank those of you who had some sincere input. I got the engine to turn over via the crankshaft/harmonic balancer, but with much effort with the plugs out and the serpentine belt off. So, I think I probably have an internal engine problem. Those of you who just saw fit to make some sort of child's BS remarks, you should actually sit back and really take a look at what you posted. These forums are intended to assist and give HELPFUL advice. Just because you have posted hundred's and even thousand's of times does not mean you are a expert at anything. The moderators should take a closer look at the posts and deal with members who just make posts to add to their profiles.
Click to expand...


Ok so the world is not perfect... bottom line did you remove the drive and try cranking it over as suggested ? This would eliminate any issue with drive, ujoints, or gimbal bearing. If you still have issue pull engine and disassemble.
 
Have not removed the drive yet to do further testing. Not looking forward to pulling engine. Might just scrap it, not sure yet. Hey o2batsea, fellow d^^k, lol. Thanks to all for the advice.
 
I have a 4.3. The engine was illding in the yard.the water was hooked to it its slow stopped like it was out of gas and locked up I cant turn engine
 
Back
Top