Mercury 402 jumping out of gear

stul · 29 August 2007, 15:42

Hi
I a have Mercury 40HP blueband 402 on last trip out on Sunday, jump out of gear after a few miles, engine just raced, low revs managed to limp home, high rev just no drive.
Had a problem selecting neutral on start up, I had used a couple weeks previous every thing fine.
Have got home now and disconnected two cables that work accelerator and gear selection. Both cables free to move with remote.
Have put engine in gear manually reverse is fine, can select neutral, forward wind engine over, but when you wind other way does not slips Clicks as if not driving.
One other thing these engines have a latches which holds engine in place when reversing (you have to put in first gear before the engine will drop down (SIT) on trim position peg (manual trim) these latches are not clearing.
Do you think this is a full strip down or Leg gearbox or Adjustment position problem, When i came to use as i said problems finding neutral and gear selection difficult

Drained oil out of leg mixture of water and oil

Advise on stripping leg gearbox if required please any useful links to advice sites would be good many thanks.
Stuart.
ps which are the more modern engine the blue or red band Mercury

Chris · 29 August 2007, 19:14

That sounds pertty terminal to me, if there is water in the oil then new seals are a must however if it is not holding forward gear it sounds like the water has already done its damage. Rebuilding a gearbox is not cheap and not something many can manage as a DIY project, you may be better off looking for a s/h gearbox to bolt on.

Chris

Nos4r2 · 29 August 2007, 20:57

Isn't that the engine with low compression on one pot?

Regardless of the state of the gearbox internals if there's water getting into the gearbox in an engine that old you might as well buy another engine-the repairs will cost more than it's worth.

stul · 30 August 2007, 03:58

Yes
looking for the right engine,life is more of a challange with limitted cash,was trying to nurse along untill right one for right money anyone know off 50 hp decent engine .
stuart

9D280 · 30 August 2007, 08:54

Sounds like excattly the problem I had with my 1973 Johnsorude. I suspect the teeth on your dog clutch / forward gear are now at 45 degrees to where they should be, net result is it pushes it back out of gear when you power on, rather than the force turning the propeller. As Forward is generally used more then reverse, that's why it goes backwards OK (i.e the reverse teeth are still in one piece).

As for reapairs, I guess if it's a "Blue band" then you probasbly want to find somewhere that will either sell you a complete gearcase or a set of gears. I picked an entire geartrain up (including the prop shaft to repair my Johnsorude for £25 about 5 or 6 years ago. Might be a tad more for a 40, as they'll be bigger gears and I guess good old inflation will have done it's job as well. If you're mechanically minded, it's not too difficult a job to split the gearcase and replace them. Just make sure it's sealed properly when you reassemble.

Places I've found obscure (i.e. old!) spares at sensible prices are BIll Higham in Manchester, Boating Mania in Upminster (tho' it doesnlt look like it from their website), Walkers Marine in Rayleigh (Southend way) and Ardoran by Oban. Google them to find the contact numbers, as it really does depend what old engines they happen to have and are breaking for spares.

Hope this helps.....

Chris · 30 August 2007, 09:31

Its worth checking the ebay USA as there are loads of people selling gearbox bits here.

Chris

Chris · 30 August 2007, 09:34

http://search.ebay.co.uk/search/sear...&fsop=1&fsoo=1

Chris

stul · 31 August 2007, 02:53

Thanks for replys
will have a look to see how bad damage is and work from there,Do you remove Pro shaft first ?
Stuart

9D280 · 31 August 2007, 08:28

Stul,

If you are looking at the gears you'll need to split the case & remove the entire shaft & gear assy as one. Prop off first, then undo the screws that hold it together. Just be careful when you prize it apart - the lever to chuck the dog back & forth along the shaft may or may not just drop out - the Johnsorude '72 consists of a fork which pivots on a pin in the upper half of the casing, and has two fingers running in a groove in the middle of the dog, and the whole lot (shaft + dog + gears) just lift out (well, if it's upside down, otherwise they drop out as you remove the bottom casing!) No idea how the dog is moved on yours, but it will be a similar arrangement.

Pulling the shaft out without splitting the case will be impossible, otherwise you''d loose it every time you engaged reverse!