Running Unleaded fuel in older big outboards

[ugboot]

I went to the local mercury service centre to buy a gasket for an 79 model 150 mariner, the owner told me he has 13 blown up big outboards since xmas due to using unleaded fuel in motors designed for leaded fuel
Ive been running premium unleaded (98 ron) for three seasons with no problems sofar . he reckons i should be putting nulon in my fuel . has any one blown up since not using lrp in an old big out board

[Kerry]

Go back and ask if that was "old" unleaded fuel ???

Cheers, Kerry.

[nisrol]

HI ugboot
Got the same outboard as you at least i think that is the case ,
have been using unleaded fuel in mine for the last 2 yrs have not had a prob with it .
reading from the workshop manual the only APPROVED gasolines for v6 models are REGULAR LEADED and premium with minimumpump posted octane number 89 or reaserch octane number94. Use of any other octane gasoline will void the warranty .
this is straight out of the MARINER outboards v-6 H.P. service manual
If you would like any more info from this manual would be happy to let you have a look at my donk also we could compare conditions and ages ?
just p.m. me for my addy and your welcome .

cheers andy

[bungie]

I have a blueband 140 (was a 150) running it on regular unleaded for a year, went to premium unleaded, for a few months, and then was only able to get reg unleaded. Found it ran sh$t loads better on reg unleaded.

[NQCairns]

Yeah like Kerry said, leaded fuel has not even been available at vehicle pumps for 5 or so years, not just XMas.

Being V6s I would assume large underfloor fuel tanks in weekend warrior boats (not that there is anything wrong with that!) that sometimes due to other reasons these days dont get used for a couple of months at a time. Not the fuels fault. Unless they all got a bad (imported?) batch somewhere? nq

[tideline_two]

outboards made in the us will run fine on 87 octane unleaded.

[Kerry]

outboards made in the us will run fine on 87 octane unleaded.

Yeah but fuel made in Oz is sh.. compared to other parts of the world.

Cheers, Kerry.

[QldKev]

In my evinrude 1977 55hp I've ran ULP for 6 years, no problems at all. PULP may cause problems long term as it takes longer for complete combustion and can still be burning aggressively when it enters the exhaust chamber.

[tideline_two]

i don't know about yalls fuel.( i live in the u.s). we've had unleaded only for about 15 years i think. i run two 140 hp johnsons on my 21 stamas. no problems. got a 35 evenrude on my creek boat. no problems. the 140's are 1996 models. the 35 is a 1987 model. 87 pctane is all thats ever been run in any of them.

[tideline_two]

forgot to add. prior to repowering in 1996 i ran 2 115 hp 1979 evinrudes 87 octane in them also no problems.

[ugboot]

Yeah like Kerry said, leaded fuel has not even been available at vehicle pumps for 5 or so years, not just XMas.

Being V6s I would assume large underfloor fuel tanks in weekend warrior boats (not that there is anything wrong with that!) that sometimes due to other reasons these days dont get used for a couple of months at a time. Not the fuels fault. Unless they all got a bad (imported?) batch somewhere? nq
hi nq
LRP is lead replacement fuel and was withdrawn at all servos around the central coast nsw around crissy apparently this will happen oz wide eventually.
the thing is lrp was 95 RON and that is above the recommended minimum for mercury mariner v6 pulp is well above but unleaded is below at 92 RON so detonation at 18-20 degrees BTDC (WOT ignition Advance Setting on the big v6) is a possibility maybe even a probability with unleaded who knows.
Also these new fuels deteriorate fast and dont like to be pre mixed, the 98 ron pulp smells like thinners not petrol.

[ugboot]

i don't know about yalls fuel.( i live in the u.s). #we've had unleaded only for about 15 years i think. #i run two 140 hp johnsons on my 21 stamas. no problems. got a 35 evenrude on my creek boat. no problems. the 140's are 1996 models. the 35 is a 1987 model. 87 pctane is all thats ever been run in any of them.
hi T2
there are 2 ways to rate octane 1 is pump octane rating and the other is Research Octane Number or RON so 87 pump Octane works out at around 94 RON and both those numbers are the minimum unleaded for big v6 mercury/mariner, here in the land of OZ we like to use big numbers so the servos rate the fuel with the RON but our unleaded is only 92 RON and PULP is either 96 or 98 depending on what servo its from.
cheers Ugboot

[NQCairns]

Yeah all LRP used to be is premium with some upper engine lube added, I can still remember the experts telling us that LRP upon introduction was just as vehicle friendly as leaded ::). For some reason 50% of cars started pinging at the lights ???and another 30% were real pains in the butt to start on a cold morning ???- experts who needs them.
Now it's digital TV, never had so much broken reception before, I wonder how much the experts need the consumer to spend this time to make their opinon correct :-X
Still shirty over that fuel con job, now we have to face a future onslaught regarding ethanol in fuel, not only will we be burning fossel fuels but also raping nature above ground to make it happen. !0% ethanol = 5 to7% worse fuel economy. What a con, I hear money talking yet again.nq

[dnej]

Hey Ugboot, did you know that your 79 Mariner , is actually Yamaha made? I bet you have had a fantastic run out of that motor.
David