dumb question alert.

[PowerAddict]

Well, in my service manual for my 73 merc 140, it says use 93 octane fuel, that is leaded. Well, obviously, we don't' have leaded fuel anymore so...

I don't know if hardened valve seats were ever installed so, what type of fuel do I use? Do I need a lead additive every time?

Thanks and sorry.

 

[wire2]

Re: dumb question alert.

"93 octane fuel" doesn't necessarily mean leaded, just premium. Although I don't see why a boat needs premium. Most are 9:1 or less compression.

 

[ziggy]

Re: dumb question alert.

i use premium + lead substitute. useing the lead substitute is controversial at best as to weather it's nessiary or not.

 

[Haut Medoc]

Re: dumb question alert.

I would use regular & throw in the additive......
A 35 year old motor will need a valve job soon anyway....
The money you save using regular can go towards that ......​

 

[Buttanic]

Re: dumb question alert.

http://www.chevron.com/products/prodserv/fuels/bulletin/unld-gas/

 

[Haut Medoc]

Re: dumb question alert.

http://www.chevron.com/products/prodserv/fuels/bulletin/unld-gas/

Good post!.......

 

[PowerAddict]

Re: dumb question alert.

yeah, I thought it was weird that they wanted higher octane fuel when compression is 8.5:1.

it says "DO NOT USE lead free or no-lead fuels." at the bottom of the page.

but I guess you guys use regular 87 ocatane unleaded fuel and have no problems?

 

[PowerAddict]

Re: dumb question alert.

http://www.chevron.com/products/prodserv/fuels/bulletin/unld-gas/

so according to that, Mercury designed all engines to run on unleaded and installed hardened seats from the factory?

the only thing they don't delve into more is octane rating. they just say the only concern is with octane. does that mean run higher octane?

 

[HT32BSX115]

Re: dumb question alert.

I had a 1966 Mark Twain 18' boat that my dad bought new. It had a 230cu-in inline 6 in it and it got unleaded fuel most of it's life. The hr meter indicated 1600hrs or so when it failed in the early to mid 80's. (he never replaced it)

I got it in 1997 and ran it until 2005. The head had never been off and I never put anything but unleaded regular in it.


You probably won't have a problem with regular unless it pings. If it does, put mid or premium in it or retard the timing a little.
Octane booster does a great job of increasing the profits of those who sell it.


Cheers,

Rick

 

[PowerAddict]

Re: dumb question alert.

alright, than I suppose I'll just go ahead and put in regular.

thanks everyone.

 

[QC]

Re: dumb question alert.

Does the service manual note RON or MON for Octane? If it is RON, then subtract about 4 - 5 points for comparable gas today at US pumps i.e RON 93 would be about 88 - 89 using the US system today

 

[PowerAddict]

Re: dumb question alert.

is RON research octane? If so, it does say "93 Research octane Min."