Perking Up A 1965 90hp 6 cyl

[dropbear68]

What can be done to my old 90 to get her going a bit more?

 

[dropbear68]

Why do mercs run 2 coils? Is there a way to upgrade the spark, thunderbolt ig any better then points

 

[Scott Danforth]

sell the 90hp, convert it to cash, use cash to buy a 150hp.

 

[Faztbullet]

No hop ups ........

 

[racerone]

Two coils was 1950 technology.-----After all these motors run at 5000 RPM and fire every stroke.----Folks were impressed by that technology.-----Most did not have a colour television either !!

 

[merc850]

Do you have the points disk for setting the point phasing?
It's important. If you have a tach you can find the right prop to give you 4800-5200 rpm.

 

[dropbear68]

Merc850 indont have the plate u speak off, its actually a 65 model, im going to keep it.

 

[Chinewalker]

If the motor is otherwise running okay, you'd be best working to get it running perfectly. Set timing per spec, prop to top end of recommended RPM, make sure compression is even across the board, and motor height & angle are optimized.

 

[merc850]

You should buy the "1965 and prior manual" Mercury manual it will guide you on all procedures such as LU, powerhead and specs. For a tach you can buy an alternator driven one instead of running around looking for a points one and if you are going to examine the points remove the red side inlet cap first! I have a printable version of that disk but It's too large to post.

 

[jimmbo]

You should buy the "1965 and prior manual" Mercury manual it will guide you on all procedures such as LU, powerhead and specs. For a tach you can buy an alternator driven one instead of running around looking for a points one and if you are going to examine the points remove the red side inlet cap first! I have a printable version of that disk but It's too large to post.

I was looking thru that manual yesterday at my dealer. Good book with lots of info. Shows all the weird remote control systems merc had in the 50s. Also shows servicing the imfamous automatic transmission. A good explanation of why Mercury developed their own oils in the sixties in there too.

 

[merc850]

The oil is probably the most critical part of any engine try running without it!, I remember when marinas sold 50:1 gas/oil mix at the pump and who knows what kind of oil was in the tank - could've been automobile grade because it was cheaper! In my years of boating I have taken apart many Mercs and I am convinced that the attitude "it's all the same oil" is responsible for the trashing of most motors. The manual shows the proper way of mixing it too.

 

[dropbear68]

Oils aint oils or so says Castrol lol, we used to get pump fuel too my old man always said a little bit extra oil wont kill it, smoke like a beauty on start up but thats half the fun of old 2 strokers the smell and smoke lol , ill pull the head and check it out for piston slap if it looks ok bore wise I wont disturb it, i figure its going to be more then enough power for the shallow draught 13 footer its going on, maybe little too much but doing this is me lol back to oil there are many decent synthetic 2stroke oils on the market now, how do these motors respond to modern fuels our base fuel here is a 94 point, we can get upto 97 octane at the pump probably closest to the old fuel u can get these days can drop some lead replacement into the fuel, im thinking piston preservation


Mod EDIT Language

 

[DavidMoore]

Being european myself I have no knowledge of your US fuels, but I can tell you the 95 octane fuel I use works just fine.

IMHO a lead replacement would be waste of money; you don't have any valves to lubricate, get the timing right and run it on the rich side and pre-ignition should't be an issue.

 

[racerone]

And what " head " are you going to pull to check piston slap ?----Are you aware of the desigm of this motor ?

 

[DavidMoore]

Just a little more on the fuel; whilst the engine should run fine with fuel from the pump (so long as it's mixed at the correct ratio with a good quality 2-stroke oil), the original fuel lines will complain bitterly about the modern fuel. Not good bedfellows at all.

If not done already, for trouble free boating, you should change them out for the newer ethanol resistant lines.