Fuel Mixture Suggestions - 1971 4HP Lightwin

[canadian_fisher]

Hello Fellow iBoat-ers.

I was given this little 4HP motor as a kicker for trolling beside my 100HP Merc.
It "barely" runs as it definately needs a little TLC.
Probably needs a carb kit and possibly a fuel pump.

Here's the question:
I notice a few folks mentioned to use a "better" than 50:1 fuel mixture for this outboard.
What do the iBOAT experts think? (40:1, 25:1)

Cheers CF

 

[Xcusme]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

I use a 32:1 mix on both of my 4hp motors.

 

[CFronzek]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

When you increase the oil content you are making the mixture a little more lean. If your carburation is on the lean side and your rings are worn enough to to let combustion gasses leak into the incoming charge you may be pretty lean already.
Why not find out what you have.? A compression check will give you a clue as to how good or how worn this motor is.
Fresh lube , check the spark and clean the carb.

 

[canadian_fisher]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

Thanks folks.

Compression = 95-PSI both cylinders
Spark = Bright blue

Carbs and/or fuel pump definately need TLC.
I am already ordering a carb kit and fuel pump as a start.
Motor won't start unless a spray fuel mix directly into carb opening.

Cheers. CF

 

[tashasdaddy]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

you're on the right track.

 

[F_R]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

As you have already found out, some people think it needs more oil, but I wouldn't hesitate a minute to run it on the factory reccommended mix of 50:1 using a good quality TC-W3 outboard oil. If it blows up, it was going to do it anyway.....from some other cause than oil. Just my 2 cents worth.

 

[canadian_fisher]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

Doohhhh....... Fuel pump is NLA (OMC 381815).
One website suggested cross-reference (OMC-388684) but the dealer quoted me $75 for the pump and didn't guarantee it was the right cross.

Any suggestions??
Maybe I do more diagnostics before spending $$.

CF

 

[canadian_fisher]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

As you have already found out, some people think it needs more oil, but I wouldn't hesitate a minute to run it on the factory reccommended mix of 50:1 using a good quality TC-W3 outboard oil. If it blows up, it was going to do it anyway.....from some other cause than oil. Just my 2 cents worth.

Yes I would agree, I always spend good money for good 2-stroke Oil.
Bad oil = broken motor = less time fishing.

Thanks. CF

 

[rickdb1boat]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

It's the small square pump. Part number 388684 $43.00

Click Here

 

[cid]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

I have a '70 and the 50:1 has been good for me, tend to run wide open with traveling on the canoe.
Then trolling pretty slow
Might want to check the H20 pump too

 

[kenmyfam]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

Good quality and "correct" 2 stroke oil is vital in 2 stroke motors. Not just outboards but every type of 2 stroke motor.

 

[canadian_fisher]

Re: Fuel Mixture Suggestions - 1971 4HP Lightwin

As always, I appreciate the feedback.
I only wish that BRP included the cross-reference like the link from RICK.

Hopefully, I only need the carb kit and good cleaning to get this old-girl purring.
An Yes, the H20 pump will get a new Impeller.

Cheers....... CF