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TOPIC: Mark 75 Powerhead Removal

Mark 75 Powerhead Removal 1 month 1 week ago #130791

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Sorry if this is a dumb question:

I'm going to remove the powerhead of my Mark 75 to remove the cowl and get at the carbs and fuel lines as well as clean it. The service manual doesn't go in to much detail on removing the powerhead, so I wanted to check ahead.

Do I need to mark anything regarding timing before I proceed? FWIW, the timing belt already broke. Also, any other words of wisdom? TIA!

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Re:Mark 75 Powerhead Removal 1 month 1 week ago #130801

Just remove the bolts and etc. and pull up.

Those are great motors! Have a Mark 78 myself and love it.


Jeff

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Re:Mark 75 Powerhead Removal 1 month 1 week ago #130818

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Awesome, thank you!

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Mark 75 Powerhead Removal 1 week 5 days ago #131253

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Ok maybe I'm just not strong enough..but I took 8 nuts off of the bolts connecting the powerhead to the lower cowl but it will not lift off. The whole motor comes with it.

Pry bar and mallet? Protein shake?
The following user(s) said Thank You: dave bernard

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Mark 75 Powerhead Removal 1 week 5 days ago #131254

Yes be cafefull with the prybar. sometimes it is the gasket and sometimes it is the studs are frozen.

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Mark 75 Powerhead Removal 1 week 5 days ago #131277

Cool motor. have a couple myself.
Assuming you have all the nuts off (Look closely!)
Try reinstalling the two nuts in the front of the motor enough so you don't damage the threads at the ends of those studs when prying up on them. Run the nuts down about flush with the ends of the studs still leaving a gap between the nut and the bottom of the cowl.
Now you can take a thick flat head screw driver or small pry bar and pry up on those nuts alternating between the two.
Once you see movement take your big flat head screw driver and put it in between the powerhead and driveshaft housing slowly working your way all around the powerhead.Work slow being careful to not chew up the mating surfaces. Don't forget to remove those two front nuts once it's all loosening up..
Once it's loose you need to pull STRAIGHT UP as the driveshaft is still in the crankshaft acting like a big dowel.
The whole shebang lower cowl and all will come off together this way.
It's a 'big'un so either use a chain fall/cherry picker/big friend(s) or whatever to pull it off. Once you get it past shoulder level it will be a load....Ah Mercury world...:<D
Get after it!

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Mark 75 Powerhead Removal 1 week 5 days ago #131278

Because of the way the shift shaft is connected, you will need to lift the power head, and leave the lower engine pan on the drive shaft housing.
You will need to remove the (8) nuts (9/16" wrench for the 3/8" fine thread nets)
You will want to remove the (4) small Phillip's head machine screws that secure the internal harness to the engine pan.
Disconnect the fuel hose from the lower fuel pump coming from the bayonet disconnect to the fuel tank.
Disconnect the wires on the (2) coils. Label them for later. Disconnect the high voltage (center) lead at each coil.
Disconnect the rectifier's main nut that secures it. (9/16" wrench)
Remove the small spring clips that hold some of the wires to the top edge of the engine pan.
Zip-tie the rectifier (with its wires still connected) up out of the way.
Remove the nut at the bottom end of the vertical throttle lever on the port side & push the small link out of the vertical lever. (3/8" wrench required)
OR,...If that little nut refuses to cooperate,...
Remove the shift cable connector outside of the engine pan (two 3/8" end wrenches or sockets required) Watch for the wave washer as you remove the related nut & cap-screw.
Then remove the cap-screw that the shift link swivels on in the bottom & inside surface of the engine pan. (9/16" wrench)
Remove the cotter pin connecting this link to the shift link inside the engine pan.
Push this main link that passes through the slot in the engine pan - into the engine pan.
Zip-tie this link up out of the way.
If you are working with a fresh water only motor, you can probably remove the small cap-screw (7/16" socket) that holds the ground strap from the engine pan to the lower aft area of the port-side water-jacket cover. If the cap-screw refuses to move, I would cut the ground strap, and deal with the seized cap-screw later while the power head is on the work bench where heat can be applied.
I 'think' that is all you'll need to disconnect,etc to lift the power head.
doc

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Mark 75 Powerhead Removal 1 week 4 days ago #131284

I was sleepy last night but this is a dock buster right?

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Mark 75 Powerhead Removal 1 week 4 days ago #131298

Shift shaft?

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Mark 75 Powerhead Removal 1 week 4 days ago #131299

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Just a Mark 75 from the plate ID.


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Mark 75 Powerhead Removal 1 week 4 days ago #131301

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Dr_Frankenmerc wrote: Because of the way the shift shaft is connected, you will need to lift the power head, and leave the lower engine pan on the drive shaft housing.
You will need to remove the (8) nuts (9/16" wrench for the 3/8" fine thread nets)
You will want to remove the (4) small Phillip's head machine screws that secure the internal harness to the engine pan.
Disconnect the fuel hose from the lower fuel pump coming from the bayonet disconnect to the fuel tank.
Disconnect the wires on the (2) coils. Label them for later. Disconnect the high voltage (center) lead at each coil.
Disconnect the rectifier's main nut that secures it. (9/16" wrench)
Remove the small spring clips that hold some of the wires to the top edge of the engine pan.
Zip-tie the rectifier (with its wires still connected) up out of the way.
Remove the nut at the bottom end of the vertical throttle lever on the port side & push the small link out of the vertical lever. (3/8" wrench required)
OR,...If that little nut refuses to cooperate,...
Remove the shift cable connector outside of the engine pan (two 3/8" end wrenches or sockets required) Watch for the wave washer as you remove the related nut & cap-screw.
Then remove the cap-screw that the shift link swivels on in the bottom & inside surface of the engine pan. (9/16" wrench)
Remove the cotter pin connecting this link to the shift link inside the engine pan.
Push this main link that passes through the slot in the engine pan - into the engine pan.
Zip-tie this link up out of the way.
If you are working with a fresh water only motor, you can probably remove the small cap-screw (7/16" socket) that holds the ground strap from the engine pan to the lower aft area of the port-side water-jacket cover. If the cap-screw refuses to move, I would cut the ground strap, and deal with the seized cap-screw later while the power head is on the work bench where heat can be applied.
I 'think' that is all you'll need to disconnect,etc to lift the power head.
doc


Wow! Thank you thank you thank you!

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Mark 75 Powerhead Removal 1 week 4 days ago #131302

not shift shaft it is a reverse lock shaft.

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Mark 75 Powerhead Removal 1 week 4 days ago #131308

Yuppp,...Reverse lock linkage, like Dave said - not a shift shaft.
GULP,...
doc

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Mark 75 Powerhead Removal 2 days 17 hours ago #131423

Yeah it is direct reversing.

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Mark 75 Powerhead Removal 1 day 23 hours ago #131433

Yuppp,...No argument there.
It's a DR,...Or "dock buster".
The 'reverse lock rod' just happens to extend up into the engine pan in the same position as the FGS (full gear shift" models), but requires a disconnect on the top side of the pan to keep the engine pan attached to the DSH (drive shaft housing) when attempting to lift the power head separately.
I have (6) fully assembled DRs, and probably about (5+) separate, but fully dressed power heads, so I 'know' my DRs.
I must have had one too many toots when I posted.
Sorry everybody.
doc

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Mark 75 Powerhead Removal 1 day 19 hours ago #131435

I was not arguing a point. Nothing to prove here. Merely pointing out to Metalhed what he has.
I hope he can make some blue smoke.
:<D

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Mark 75 Powerhead Removal 22 hours 23 minutes ago #131453

I'm sorry Clyde,
I wasn't trying to argue either.
Just trying to clarify my error.
I'm a Mercaholic to the bone, and I appreciate fellow Mercaholics keeping me squared away.
doc
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Mark 75 Powerhead Removal 4 hours 36 minutes ago #131473

No offense taken. I am a confessed outboardaholic. It all started with a little Sea King now and again, on to the Champions, Atwaters and usual OMC poisons. Then of course on to the heavy stuff a long string of Mercs finally landing in this never ending pit of despair of McCullisism...
I am a sick man.
:<D
But a happy man.

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