Yamaha Outboard Motor

[Fire99]

Hi All..
Thanks for all your previous help. Unfortunately i have another issue, quite a big one which i would like some help on if poss.
I have a Yamaha 40hp Outboard on my Norman 18. I recently had a £700 engine rebuild done including Main Outer Bearings on the Crankshaft. I was told that the centres were a little suspect but you would need to split the crank to replace them and it would cost a fortune. So a slight gamble was made.
Anway the motor ran perfectly but 2 weeks ago a dreadfull knocking occurred which on inspection by the outboard shop was the centre Piston had hit the head, so obviously something had gone within the centre main bearings.. No warning ..no rumbling..just bang. Anway, the outboard shop said it is unecconomic to repair the motor and have offered to give £500 p/ex for another engine.
A friend in the engineering trade suggested trying to tackle the job of repairing the outboard myself and he would sort the mild pitting on the head.
Firstly, does anyone have any advice on tackling a job like this.. (It has new outer main bearings, new water pump,oil pump etc.)
Secondly, is it a major task to split the crank..
Any advice would be greatly appreciated.
thanks
Nick

 

[Col]

Like most jobs, not difficult if you have tools.
Where do you live ? There is a place not far from me that could do your crank for you.

 

[DepSol]

As an ex motorbike mechanic it wouldn't bother me to do it but only if I had the tools and the place to work on it without interuption or people moving bits.

Not hard to do make sure you have a blow torch and a hammer!

 

[Dave_Snelson]

Fortunately Yams are reasonably accessible with ordinary tools. Removing the powerhead from the unit should be strait-forward enough remembering to label *everything* A 2-stroke block has little more than 3 exterior bits, the bottom half of the case, the block and the head. New gaskets will be needed for these.

Before I go any further, have you priced up the bits? No seriously, have you priced up the bits? You may be able to get another 2nd hand motor from www.boatsandoutboards.co.uk for better than the price of new spares, or find another motor same as yours to make a good one (say with blown gearbox).

There will be a lot of collateral damage to the internals with a piston knocking the head. You should expect to replace pistons, rods, crank, head and all bearings except outers. Let me know what you find inside it.

 

[BarryH]

Dont know if youve seen decembers Boatmart, in the classifieds there is a power head for sale for a yam, about £150 i think, worth a phone call

 

[Fire99]

I am Near Southend - on -Sea in Essex.

 

[Fire99]

Thansks for the advice, as i said the people who did the original work offered £500 for the outboard as there was a degree of fault by both parties. THis is against a Johnson 40 (1988) for an extra £700 which they have just serviced with power tilt and electric start.
It is only a 2 cylinder as apposed to 3 but stll 40hp Does anyone know what impact this would have. and also are the mountings the same on the boat?
Thanks again for the info

 

[Fire99]

Thanks for the reply.. The problem i think may be parts prices for a piston, rods etc. and i've never split a crank before..