Mercruiser 7.4 engine wont turn over

[Captain_Chanse]

A few days ago boat was running great. When I got home to flush the motor it would start then stop. I found this boat mechanic on craigslist who came over a few days later and said it was the fuel pump. He replaced the pump and now the starter engages but it wont turn the motor over. The problem is not the batteries because I put my big charger with a starting position and it did the same thing.

Also how can I manually rotate this motor

Chanse

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

pulled plugs out do not see water would not turn over. Used pry bar and socket on crankshaft bolt could not turn motor.

 

[Maclin]

Re: Mercruiser 7.4 engine wont turn over

Does it have all accessories running on one serpentine belt? I had an alternator lock up on me once on a 4.3 GMC truck engine with the serpentine belt, stopped it dead cold when idling and would not turn over until I removed the serpentine belt.

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

I removed all belts and the harmonic balance pulley so that I could get a good bite on the crankshaft bolt.

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

Removed drive still acts locked up.

At the end of the yoke is the axle spline end is their a bearing at the section where the spline enters? I see a bearing where the yoke is and its spinning.

 

[Bt Doctur]

Re: Mercruiser 7.4 engine wont turn over

That would be the gimbal bearing.nothing to do with the motor turning.The nose bolt may not turn the 7.4 even without plugs.
Are you sure the starter is actually trying to turn the motor?
Try jumping the main + lug on the starter to a ground, there should be a fat spark.
Try jumping the solenoid ,main lug to small lug w/ the yel/red srtipe.,should a a small solenoid spark.
No spark=no power being supplied.Check all cable connections especially the neg. on the block.

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

Hello Bt Doctur

I attached a youtube link of what the sound is when trying to start boat.

http://www.youtube.com/watch?v=1zcb-ze2TLA

Do you think the starter maybe engaging but not turning over?

 

[Don S]

Re: Mercruiser 7.4 engine wont turn over

Do you think the starter maybe engaging but not turning over?

From the video, that's what it sounds like.
Pull the starter off, get in there with a pry bar between the block and flywheel ring gear and see if it will turn.
If it doesn't, it's locked up.
Was there any rust on the spark plugs when you pulled them?

 

[Bt Doctur]

Re: Mercruiser 7.4 engine wont turn over

What Don says, pull the starter

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

Hello, Don S

Pulled starter and it was good.

took universal joint off drive shaft yoke put yoke in the flywheel ring took pipe wrench and tried to turn No Luck!

Looks like I need a new motor anyone know where I can get a deal on short block, long block or full motor?


Chanse

 

[Bt Doctur]

Re: Mercruiser 7.4 engine wont turn over

If you can, try turning the flywheel at the teeth with a lug wrench or crow bar first.
might pull the valve covers looking for a dropped valve.

 

[Silvertip]

Re: Mercruiser 7.4 engine wont turn over

Drive locked up perhaps?

 

[Don S]

Re: Mercruiser 7.4 engine wont turn over

He pulled the drive already, see post #5

 

[bruceb58]

Re: Mercruiser 7.4 engine wont turn over

If you can, try turning the flywheel at the teeth with a lug wrench or crow bar first.
might pull the valve covers looking for a dropped valve.

That would be your best bet at this point.

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

Pulled valve covers off no dropped valve.

I cant get to the flywheel teeth because of the housing but isn't the flywheel and the female end or flywheel ring of the drive one solid piece?

If so then wouldn't me doing this be the same thing as prying flywheel teeth?(took universal joint off drive shaft yoke put yoke in the flywheel ring took pipe wrench and tried to turn No Luck!)

Thanks Chanse

 

[frank246]

Re: Mercruiser 7.4 engine wont turn over

Might be a stuppid question, but did you try to remove the fuel pump as you described that the engine would not turn over after the mechanic replaced the fuel pump?

 

[Captain_Chanse]

Re: Mercruiser 7.4 engine wont turn over

That was the first thing I did..Thanks

 

[boat1010]

Re: Mercruiser 7.4 engine wont turn over

Mine is in the shop as we speak getting a new motor put in it. I live in Nebraska. I busted a rod and decided that I would feel better replacing the motor than doing the engine work and still have an old motor. He ordered a long block, not sure where he gets them, but had it in three days. My boat is a 89 and the motor has been rebuilt once before. Good luck with yours. $4000,00 for the long block.

 

[toolsinbox]

Re: Mercruiser 7.4 engine wont turn over

Just reading this thread as I am installing my rebuilt 7.4 stove just in time for the snow and I wondered if you saw the old pump come out? Did all of it come out? Nothing left behind? If yes to all I would pull the heads and see whats what. You didnt say what shape the plugs were in. Are you sure there was no water that got in?

 

[Maclin]

Re: Mercruiser 7.4 engine wont turn over

Captain, did you try to turn the engine in both directions? Sometimes it is jammed one way but can back up some so to speak. I know how frustrating this must be