1995 Mercury 75HP Outboard won't go into reverse in the water?

m4gu1re · 21 September 2013, 18:38

Hi Everyone,

Have been recommended to this site by a friend of mine who also owns a RIB so hoping someone maybe able to help me and in the future I'll be able to do the same for someone else.

I have a 5.4M Avon Searider RIB with a 1995 Mercury 75HP 2-Stoke Outboard. The last time I took it out it suddenly stopped going into reverse and instead made a horrible shuddering noise (louder the more you put the throttle down). Having taken the boat out and flushed it through with fresh water using mufflers it went into both forward and reverse without an issue. Today I took it out again, started by flushing it through, it went into reverse perfectly

, I took the lid off the engine and checked that it when all the way in (a guy showed me where to look the previous week!) BUT once in the water no sign of reverse and the horrible shuddering again, with the lid off in the water I could see that it wasn't going into gear properly but I have no idea why it works when out of the water??

Any help would be greatly appreciate prior to me taking it to a garage and getting the "mmmmm, it's not going to be cheap discussion!"

Thanks, Ben

uncle al · 21 September 2013, 18:45

have you had the g/housing of lately?

m4gu1re · 21 September 2013, 18:47

Hi, thank you for the response. Are you referring to the lid or something within the engine?? I've taken the lid on and off but not touched anything else. This is my first RIB and I don't have the hugest amount of mechanical knowledge so learning as I go. Once I've done something once I'm fine moving forward.

uncle al · 21 September 2013, 18:55

so you havent had the g/housing of thats the g/box on the btm,try dis-connecting the gear shift cable of the OBM and put it into fwd and turn the prop by hand, MAKE SURE THAT THE IGN IS NOT TURNED ON! does it turn ok you may find that it will ratchet one way but not the other, now select reverse it should not rotate either way except for a small movement either way, if it rotates in reverse drain the oil out of the gear housing if it has mettalic particles in it Im sorry but it looks like a w/shop job.Please let me know how you get on.

m4gu1re · 21 September 2013, 18:58

Thanks for the advise. I shall have a look. I'm still baffled why it goes into reverse as normal when on the trailer and fresh water going through but in the sea a totally different story. If it didn't go into reverse at all it would make some sense!

uncle al · 21 September 2013, 19:00

it is probaly all due to water resistance when on the water.Just remember to think safety when you work on an obm

Landlockedpirate · 21 September 2013, 19:24

It could be as simple as the gear linkage needs adjusting. If it only just engages reverse it will spin the prop out of the water because (As Uncle AL pointed out) there is no resistance.

The moment you put it in the water the resistance on the prop wins over the only just engaged gears, the noise is the gears bouncing over each other rather than fully engaging.

Try adjusting the length of the cable and because its easy and cheap, change the lower leg gear box lube at the same time. Have a look on Youtube, both of these operations are on there.

m4gu1re · 21 September 2013, 19:37

Thanks for that, really appreciate advice from both. Will certainly try cheaper options prior to putting into garage!

Jizm · 21 September 2013, 20:13

What does the oil look like? I've had something similar turned out to be seals gone and water getting in the gearbox.

m4gu1re · 21 September 2013, 20:18

I mix the oil with the petrol (50:1) in the orange fuel tanks rather than it going in separately. The guy that I bought the boat off in August told me the previous owner had taken the oil mixer bit out of the outboard.

Nos4r2 · 21 September 2013, 20:35

Quote:

Originally Posted by m4gu1re

I mix the oil with the petrol (50:1) in the orange fuel tanks rather than it going in separately. The guy that I bought the boat off in August told me the previous owner had taken the oil mixer bit out of the outboard.

Jizm means the gearbox oil.

m4gu1re · 21 September 2013, 20:43

I'll have to look, wasn't even aware there was any other oil involved??

Jizm · 21 September 2013, 20:47

Quote:

Originally Posted by m4gu1re

I'll have to look, wasn't even aware there was any other oil involved??

There may not and that could be the problem!

Have a look on YouTube for checking outboard gearbox oil!!

m4gu1re · 21 September 2013, 20:48

Thanks again everyone!

Jwmarineuk · 22 September 2013, 18:20

The oil in the outboard leg is separate. It's purely for the transmission. You'll find a plug for filling and a plug for draining, try and find the manual to see how much oil it takes when replacing it. Sometimes helps to flush it through with oil, so do one oil change and then another after running the outboard for a day. Check the colour of the oil, if it's creamy and frothy it indicates water ingress.

cptsideways · 22 September 2013, 20:58

Dog clutch is worn, you might be needing a new one & reverse gear too. Yo will need to pull the gear unit out of the casing.

m4gu1re · 22 September 2013, 21:01

Would that job be on the wrong side of expensive?

cptsideways · 22 September 2013, 21:07

New parts yes, 400 quid plus, a replacement gearbox might be a better bet

m4gu1re · 22 September 2013, 21:09

How much would I be looking at for one of those? The guy who sold it to me said it was replaced last year. Seems I've been well and truly had!