Mercury 75 is tight

[michael.mathias]

Hi everyone, I have a Mercury 75 outboard 4 stroke, used it last year up until October flushed and left it until this year. It now barely turns over. I took all four plugs out and it turns over ok but doesn’t fly. I have sprayed WD40 into the cylinders but it’s made no difference. Someone said it could be a tight water pump but any help would
Be appreciated

 

[Hot Property]

That's a pretty bullet proof engine I've had 2 of them.

If you are mechanically minded, drop the leg to check the impeller and water pump housing. Change the leg oil and check that the driveshaft rotates easily.

If the oil is emulsified then it's likely that one or more oil seals need replacing.

The engine should turn over easily with leg removed.

There is a middle bush that supports the driveshaft. Check it's in good condition and that the ally housing hasn't corroded etc.

I'd be interested to know what you find!

 

[michael.mathias]

That’s a great call, I will try and do this tomorrow.. thank you

 

[michael.mathias]

Ok so I have taken four bolts out on the bottom leg and the one up under the prop, I can only get the gearbox about a half inch loose?? Am I missing something?

 

[SC35]

Is there a gear shift rod that needs to be disconnected?

 

[Hot Property]

Is there a gear shift rod that needs to be disconnected?

There is a gear shift rod to loosen.

Make a note of the nuts position on the threaded rod otherwise you will have fun setting FNR when you reassemble!

 

[michael.mathias]

There is a gear shift rod to loosen.

Make a note of the nuts position on the threaded rod otherwise you will have fun setting FNR when you reassemble!

Any idea where it is located? Sorry looked for it and can’t see anything

 

[Hot Property]

Any idea where it is located? Sorry looked for it and can’t see anything

From memory you prize off an approximately 50 mm rubber bung on the leg. You can download a workshop manual for free if you search hard ...

 

[michael.mathias]

There was no top bolt…… I have dropped the leg and omg was it tight!!!! There is a bit of scoring on the shaft as shown in the pictures. Is it an issue? Also do I just lube it up and replace or do I need to change something?

 

[michael.mathias]

Sorry forgot the pics

 

[Hot Property]

Have you undone the anode bolt?

Sorry forgot the pics

Just clean the wider part of the shaft with fine emery cloth. Clean out crap from the splines and grease with 2-4-c - so when you take it off again it actually comes out!

The casing around the middle bush seems intact and judging from the marks on the wider part of the shaft it still has some life in it. Smear a dollop of 2-4-c grease on the wider part of the shaft as well - it will help lubricate the bush.

 

[michael.mathias]

Have you undone the anode bolt?

Just clean the wider part of the shaft with fine emery cloth. Clean out crap from the splines and grease with 2-4-c - so when you take it off again it actually comes out!

The casing around the middle bush seems intact and judging from the marks on the wider part of the shaft it still has some life in it. Smear a dollop of 2-4-c grease on the wider part of the shaft as well - it will help lubricate the bush.

No I didn’t undo the anode bolt?? Thanks for your help I couldn’t have done it without it… so grateful…… I am going to change the impeller while it’s off and the oil…

 

[Hot Property]

No I didn’t undo the anode bolt?? Thanks for your help I couldn’t have done it without it… so grateful…… I am going to change the impeller while it’s off and the oil…

Good idea to do the impeller, its a faff to do so save yourself some time to go boating!