Evinrude 70 2 Stroke (1980??)

[rosemb]

Hi,
I have a 70hp 2 stork Evinrude outboard. Just checked the plugs and they need replacing,. What is the recommended replacement spark plug type and gap setting? I notice that the bottom plug diameter is bigger than the upper two spark plugs

 

[bob johnson]

Re: Evinrude 70 2 Stroke (1980??)

they should all be the same size is my guess......

it is highly likely that the lower cylinder had its plud threads stripped out and they went ahead and tapped for a larger spark plug.

I am pretty sure the plug that the motor normally uses is a VERY common plug

I dont remember it right now..

ok looked it up...OMC 1989 manual for a 70 hp

recommended QL77JC4
alternate L77JC4
sustained high speed QL78V
alternate high speed L78V

good luck

if you got as larger size plug thread in one hole...you got to make a choice of a plug that is about the same heat range as the ones you will use in the other two cylinders.. ahhh outboard motors!!!


bob

 

[rosemb]

Re: Evinrude 70 2 Stroke (1980??)

Thanks for the reply, will try to find an equivalent plug for the lower cylinder

 

[rosemb]

Re: Evinrude 70 2 Stroke (1980??)

Hi

The bottom cylinder head spark plug boar has been increased to a next larger size due to someone stripping the thread, any recommendations on spark plug type and gap size for the bottom cylinder?

 

[wilde1j]

Re: Evinrude 70 2 Stroke (1980??)

Remove the head and take it to a machine shop to get a correct size Helicoil installed. They don't make the "right" plug in different thread sizes. If the head is too crapped up, get a used one from one of the many OB parts recyclers such as tcoutboards.com, etc.

 

[bob johnson]

Re: Evinrude 70 2 Stroke (1980??)

you MIGHT.....be able to find an adapter which will have males threads the size of the larger spark plug... and femal threads the size of the plug you should beusing...

as we all should know taking a head moff might lead to even bigger problems than a odd ball spark plug..

it isnt feasable that all the head bolts will come off with out at least ONE breaking....the motor is at least 25 years old or there about

if it were me, Id ask and ask till I found a temperature range similar to the one that should be used.. and just go with that...as long as the plug does not protrude too deep into the cylinder !!

good luck

bob

 

[wilde1j]

Re: Evinrude 70 2 Stroke (1980??)

I don't agree about removing the head. If you do it right, there's absolutely no reason to break a head bolt.