Which fuel should this motor run

[fishweed]

When I purchased my boat this past summer, the owner stressed several times that the motor only ran well on 93 octane gasoline. The motor is a 1993 Johnson 200 GT Venom. I took his advise and ran the motor on 93oct all summer with no problems.<br /><br />I want to try lower octane fuels this season for money savings, but I do not want to hurt the motor or performance in an effort to be cheep. What do you experienced boaters say?

 

[llfish]

Re: Which fuel should this motor run

My limited knowledge tells my 87 octane. Someone will come along who definitely knows.

 

[JB]

Re: Which fuel should this motor run

Hi, Ken.<br /><br />The only thing that 93 octane will do for you is lighten your wallet.<br /><br />The engine was designed for 87 octane and that is what you should run in it.<br /><br />Good luck.

 

[Paul Moir]

Re: Which fuel should this motor run

Is it possible the previous owner modified it at all?

 

[LubeDude]

Re: Which fuel should this motor run

A higher octane fuel, due to the fact that it burns slower will sometimes noticably make the engine sound quieter, especialy an outboard. Therefore, people assume that the engine is actually running better when in fact you may be losing performance and carboning things up. I would do a good decarb this spring and then switch to 87. Bet the decarb makes a big black mess.

 

[fishweed]

Re: Which fuel should this motor run

I think the boat was suffering from lack of proper maintenance. Like I said before, the boat ran fine all summer other than being a bit hard to keep running at low idle until warm. This fall I took the boat to my local machanic for an end of season tune up before I winterized it. The report back from him was that the linkage to the carbs was way off, the timeing was way off, the wrong plugs were installed at the wrong gap,0.1 ,. Yes that is right, gap at 0.1 ,.He wanted to know if the thing even ran before he corrected everything.<br />I wondered if this is why the owner recommended 93 octane fuel, because anything lower would not perform. ?????

 

[Paul Moir]

Re: Which fuel should this motor run

LOL - That would certainly explain a lot! I was just worried he had shaved the heads in an attempt to 'hop it up'.

 

[LubeDude]

Re: Which fuel should this motor run

A good "Link and sync" buy the dealer is very good maintenance practice, a good dealer will usually only charge you an hour or less, and its money well spent.

 

[walleyehed]

Re: Which fuel should this motor run

This is from Marine Fabrication INC's (MAR-FAB) notes on break-in for my 200 with GT heads;They done the machine work, I built the engine...<br />Double oil, TC-W3 for first 30 gallons of gas, 91-94 octane with NO Alcohol (Continue to Use 92-94 octane premium grade after break-in)Allow 4hrs Idle only for piston and ring break-in, Avoid full throttle for first 10 hours...

 

[Dhadley]

Re: Which fuel should this motor run

Ken, you first have to know what the previous owner did to it. Shaving the heads might do it. Depends on how far he cut them. Or running small bore heads on the big bore motor requires hi-test. <br /><br />Be careful running anything other than Champion plugs. Be very careful with the timing. When the mechanic reset the timing what did he set it to? And by what method?

 

[fishweed]

Re: Which fuel should this motor run

Thanks to all that have helped me now and in the past. All of you are great!! The next round is on me!!!<br /><br />Dhadley, I do not think any machine work has been done to this motor. Everything looks factory under the hood, other than the motorcraft plugs he had in it.<br />I wish that I was smart enough to know how the mechanic reset the timing. I am sure he did it the right way. He is almost as good a fellow as you's guys!

 

[walleyehed]

Re: Which fuel should this motor run

Must be a super guy......