Octane Change

[mikeg205]

found this... and it calls for 93 using RON.

http://www.planetnautique.com/Correc...nersManual.pdf

[CantRepeat]

Originally Posted by mgorczak1

found this... and it calls for 93 using RON.

http://www.planetnautique.com/Correc...nersManual.pdf

You've link to page with manuals that only go back to 2007. None of the information in those manuals will be relevant to your boat.

You'd be better off with the Indmar 1993 or older manual then using one of those.

http://www.indmar.com/service-support/manuals.aspx

[CantRepeat]

Looks like my browser was messing up. Kept sending me to the main manual page.

And from the manual:

Fuel Requirements
Use any good grade automotive regular or premium gasoline with a minimum average octane rating of 88* (93 research) in your PCM engine.
An 86* average octane (90 research) gasoline may be used if the gasoline described above is not available; however, the ignition timing MUST BE retarded 41 to prevent harmful detonation.
*New U.S. Regulation requires posting average of research and motor octane.
PCM reserves the right to refuse warranty on parts which are damaged -when using improper gasolines.

It clearly says use any regular automotive fuel and can have an average of 86 octane OR premium 88. There is no doubt that 87 is just fine for that engine.

[wrobins1]

Originally Posted by madcityskier

I understand how octane works, higher octane, higher combustion point. Less perignition, greater volume in cylinder for explosion= more power. I'm not sure how changing it now could cause a problem. The original PCM service manual and MasterCraft owners manual call for minimum 93 octane, which is hard to come by. The reason for considering is the afore mentioned slight hesitation when getting into the throttle to pull my 285 lbs out of the water, particularly in April and November in Wisconsin. As I mentioned it seems that several mechanics believe this, though since they can't say why I believe it is likely to be an old wives tale.

as another >250 lbs rider/skier all I can say is when I notice that slight hesitation I remember back to learning to wakeboard behind a 17' Monte Carlo with a 4 cyl...

[madcityskier]

Originally Posted by CantRepeat

I'd like to see in writing where 93 is recommended by either PCM or Indmar for an 85 351W. I just look at the specs and it's an 8.3 to 1 motor. In stock form there is zero reason to recommend or even consider running 93. It would be a complete waste of money.

Like these pages from the manuals?

[Jeff d]

It says 93 Research Octane (RON) though. RON is more common worldwide but gas pumps in the US are labeled with (R+M)/S (AKA Anti Knock Index). 93 RON = 88 (R+M)/S. Look at the buttons on the pump next time you get gas. They will say (R+M)/S in the fine print under the "87", "89", etc. So, 93 RON = "Regular Unleaded" in most US regions.

[CantRepeat]

Originally Posted by Jeff d

It says 93 Research Octane (RON) though. RON is more common worldwide but gas pumps in the US are labeled with (R+M)/S (AKA Anti Knock Index). 93 RON = 88 (R+M)/S. Look at the buttons on the pump next time you get gas. They will say (R+M)/S in the fine print under the "87", "89", etc. So, 93 RON = "Regular Unleaded" in most US regions.

Yep, there is no reason to waste money on 93 when clearly it will run on 87. I would be more concerned about the valve seats and running unleaded fuels.

Here is a link to a nice RON/MON conversion.

http://www.btinternet.com/~madmole/R...RONMONPON.html

With this you can see that a 93 RON is close to 86 or 87 so using regular 87 is going to just fine. Once again, lead seems to a bigger concern unless hardened seats have been installed.

[oldairboater]

Run the octane level that does not knock under load in the summer. Too low an octane level in a hot engine helps cause early ignition. The only problem with running lower octane levels is that most people can't hear engine knock or don't recognize it. If you ask people what ping, valve chatter, or engine knock sounds like the answers are not always right. The higher octane gas will not hurt your engine and changing to a higher octane will not hurt your engine. You will be spending more of your dollars but not harming your engine.

[madcityskier]

All these posts and no response that says it will hurt. I'll take that as the answer.

[mikeg205]

.20 more per gallon more for the best octane controlled burn is too cheap to even debate. Unless of course you're buying on the water. I buy about 180 gallons a season so that equates to $36 - $40 bucks a season...cheap cheap for minimizing any chance for detonation, my gas always sits, I don't run my boat every week, made a few new friends so we alternate. I am kind of an additive nut so I just added Lucas Octane Boost to the gas I have been saving all winter in my boats gas tank. Weather caused be to have more gas left than I usually like to.

I have a station locally that has some racing fuel, which I might use to top off the tank.

It's a great discussion for us boat owners who want keep our older boats running for darn near forever. Considering for me a slalom skier a new PS 197 sells for about a $49,900 + sales tax + higher insurance...