1978? merc black max fuel/oil ratio and more

[bramer]

I just purchased a boat from a fellow, but don't think he knew much about the boat. he said the oil/fuel ratio is 16oz/gal. After researching this sight I think it to be more about 50:1, but there is no information on this sight about this motor. There has also been an electronic fuel pump added, and has difficulty starting but runs/starts fine once it has been started. Also any information about recommended oil and plugs, along with other important information, would be much appriciated.

 

[BaysideMarine]

Re: 1978? merc black max fuel/oil ratio and more

Hi,<br />More info re your engine please.... I would assume if you are calling it a black max then it would have to be a V6 engine? 1978 was the intoduction of the V6 and the end of the I6. 50:1 is the correct fuel/oil ratio.

 

[WillyBWright]

Re: 1978? merc black max fuel/oil ratio and more

That's a pint to 6 gallons (mathematically it works out to 48:1 but that's dang close).<br /><br />Get rid of the electic fuel pump. Make the one it came with work instead. If the diaphragm(s) torn, the motor won't run right. There's proper and improper ways to address fuel problems. Installing an electric fuel pump was definately the wrong way to go. Way more expensive as well, since fuel pump rebuild kits are ridiculously cheap in comparison.<br /><br />If you can give us the serial number off the motor, we can nail-down the year. One easy to tell is with the trim system. The early models had a massive single-ram system with the pump mounted inside the boat. That's probably the best trim unit those ever had including what they put on today. <br /><br />Any used motor I get automatically gets a water pump rebuild, fresh gearlube, and new sparkplugs. Sounds like you can add Fuel Pump rebuild to the list on yours.

 

[bramer]

Re: 1978? merc black max fuel/oil ratio and more

Thanks for the info guys. The serial # is 4967970 or the zero could be a 9. It looks like the 0/9 was stampted twice at the factory. And sorry for the lack of information before. It is a V6 black max 150.

 

[BaysideMarine]

Re: 1978? merc black max fuel/oil ratio and more

Run your new beast on premium unleaded (not sure what they call it in the US, I think it's called Hi Test??). Over here its basically 98+ octane. Regular unleaded is too low grade for an older engine although the octane ratings are different between the US and Australia.<br /><br />For oil, use Quiksilver 2 stroke (cycle) oil. It is currently rated as the best oil on the market. For gear oil use the Merc lube or if you want to get carried away with yourself use the premium lube (the MerCruiser stuff). In reality the difference between the two is the premium stuff probably has a better ability to mix well with water as water ingress on a sterndrive (probably a moored boat) is obviously much more of an issue than a trailered boat.<br />Off the top of my head I would say the plugs are going to be BUHW or BUHX, both being surface gapped, cool running plugs.<br />The early Merc V6's were not paricularly known as good engines. They had serious issues with corrosion of the block. If its a freshwater engine then no problem, but if its a salty then its something to consider.<br />One thing I must say, and I can't help myself, is that nothing and I MEAN NOTHING, sounds quite like a V6 Merc....<br />Cheers