Fuel Octane Rating

[bill durham]

I just cranked my boat up after sitting for a couple of weeks. I spun it about 10 times with no fire at all. Got out the cold start spray and after the 2nd spin, it fired and ran as it usually does, perfectly. I was told by the dealer I bought the boat from that anything above 87 octane was just wasting money. The dealer was located in Florida, and I'm having 2nd thoughts about that advice up here in North Georgia. Would a higher octane fuel have any impact on cold starting?

thanks,
BD

[Ken]

BD,
None whatsoever. If your owners manual calls for 87 octane, that's what you need. Anything higher, you're wasting money.
Sounds like you are not getting fuel to cylinders on a cold start. When you pump primer bulb, it should get hard after a 4-5 pumps, indicating it has primed fuel thru the local filter, thru the fuel pump and on to the carburetors (I'm assuming carbed).
Take a look at the local filter - clean out if necessary.
If the motor has been allowed to set up for, say, six weeks or more w/o being run, then you could have clogged carbs. Do a shock treatment with RingFree or SeaFoam. If that does not help, do a carb overhaul and kit install.
Good luck [img]smile.gif[/img] ,
Ken K

[bill durham]

Ken,

Its a fuel injected motor, I checked the fuel bowl and it was full, even squeezed the bulb a couple of times and it was hard. Not sure what is going on, but I think its fuel related somehow.

[Ken]

BD,
I believe there is a low pressure pump that feeds the injector pump - could be your problem - not real familiar with fuel injection on these motors. Also, there are some check valves in the injector pump that may be sticking on you.
If you haven't done a shock treatment with RingFree or SeaFoam in the last year, I would do it. There may be some varnish or gum in the fuel system causing you the problem. The shock treatment may do the trick - not expensive and fairly easy to do.
By the way, it would help if you told us the year and model number of your motor .
Good luck [img]smile.gif[/img] ,
Ken K

[bill durham]

Ken,

Sorry, its a 2000 SX150. I had it tuned up in the Spring, new plugs and fuel filter. I'll give it the sea foam treatment for sure, thanks for the input.

BD

[Ken]

BD,
Thanks - yeah, I later saw your model motor in another post.
I believe the Yamaha shop manual describes a procedure for testing the low pressure fuel pump and also for the injector pump. If you don't already have one, get yourself a Yamaha shop manual. You can order online at www.yamahapubs.com.
Good luck [img]smile.gif[/img] ,
Ken K

[boats.net]

Bill
Dont forget the battery, EFI engines need to have 10 volts at starting. a marginal battery will drop down below 10 volts at cranking it can affect injector driver and ECU.

[Ken]

BD,
From what boats.net mechanic is saying, you need to monitor the voltage at the motor, not the battery during cranking. You could easily have as much as 2-3 volt drop from the battery to the motor.
I would measure the voltage with a voltmeter right at the starter.
Good luck [img]smile.gif[/img] ,
Ken K

[bill durham]

Very interesting about the voltage. I replaced my crank battery a month ago. The book says something like 500 CCA is the minimum, I have a 650 CCA Everstart and it still hesitates before it spins. I suspected that my old battery was shot by looking at the voltmeter in the speedometer and it was dropping down to 8 volts during start. Even the new battery drops down almost that low.
By the way, I put a can of Seafoam in and went out fishing Tuesday...more to run the solvent through the motor than to fish. It cranked on the 3rd turn of the key and ran great all day..thanks for the suggestion.

Merry Christmas
BD