70's mercury 1150 where's the gearbox?

[bexi]

hey guys i got a 1970 blue line mercury 115hp.
I wanted to know is the gear box located in the lower unit that the impeller sits ontop of.
the reason why i'm asking is because i did a compression test on my motor and one cylinder is way down.
i've found another motor cheap but with a stuffed gearbox so thought i could use my current gearbox and the other engines motor?

 

[Laddies]

Re: 70's mercury 1150 where's the gearbox?

Yes the lower unit is the gear box

 

[renny1]

Re: 70's mercury 1150 where's the gearbox?

why not re-build the power head i am doing it now and its not as hard as you may think

 

[steelespike]

Re: 70's mercury 1150 where's the gearbox?

You also may want to consider a decarb treatment unless your sure the cylinder is kissed.

 

[bexi]

Re: 70's mercury 1150 where's the gearbox?

renny1... i was worried the parts would be expensive

steelespike... what do you mean a decarb treatment? how does that relate to low compression? one cylinder has 55psi, the rest have between 110-120

 

[Chris1956]

Re: 70's mercury 1150 where's the gearbox?

Bexi, If you want to rebuild it, the oversize pistons are about $100 each, boring will be $30-50 each sylinder, and miscellanous stuff another $50 or so. You still need to figure out why the one cylinder went bad. It is usually lack of cooling, lean mixture or overadvanced ign timing.

 

[Silvertip]

Re: 70's mercury 1150 where's the gearbox?

Carbon build up in a a two stroke motor causes rings to stick and therefore not seal as well. Decarb (de-carboning) using a high strength mixture of SeaFoam or similar products and remove carbon, free the rings and raise compression IF the problem is due to carbon. If there is a mechanical issue such as a scored cylinder, that obviously will do not good.