Low RPM's Whats wrong ? Please Help

[Stan]

I went out on my friends Eliminator on Saturday…here’s the problem…when he put the boat away last season…no problems…this year both times he went out he could only get to 4000 rpm’s on the mercruiser 350. Normal rpm range is 4600 to 4800. Whats wrong ??

Thanks

Stan

[Tom on Lanier]

Stan - how does the boat speed compare from last fall to now? In other words, is the tach working properly? If it is, it's more involved.

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Tom
"Tomahawk"

[RickR]

Take the fuel filter off and pour gas in a glass jar. Look for water and/or trash.
If you're on a budget, filter can be reused if not too dirty or rusty. Just let the water dry off the filter medium.

Is he using last year's fuel? Today's gas has a very short shelf life. Starts to go stale after 30 days. I use Sta-bil.

Is ignition advancing?

Is the hull full of water?

Did your buddy gain alot of weight over the winter http://www.donzi.net/ubb/eek.gif

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RICKR
mailto:riggerb@aol.comriggerb@aol.com</A>

[Stan]

Lets see...speed is off....some gas is from last year and 1/2 a tank of new gas. We will check the quality of the gas tonight as well as the filter. No water in hull. Doughnut factor is nill. How can he tell if the ignition is advancing and why would it be advancing now if nothing was touched since last year ? Can it be a vacume hose and how can we check that ?

Thanks

Stan

[jaroot]

First thing i'd do is pull a plug and see what color it is, if you are starving it for fuel after a hard run (wind it out for a little run and then shut it off without idling too much) they'll be chalky gray or white which is lean meaning a lack of fuel and a restriction somewhere... if they are black and sooty you have an issue in the carb dumping too much fuel in. Both conditions could be caused by a sticky needle and seat or float level, dirty or varnished jets and passages or it may sound obvious but a restricted flame retarder, youd be suprised how much crap can get in that thing... Make sure that the choke isn;t hanging up and is working properly... if it stays on you are going to seriously restrict airflow and flood the motor. And while you are at it i;d make sure all the plug wires are pushed all the way down on all the plugs and the distributor cap. Never can tell, there might have been a plug wire snagged when the motor was winterized (or do they even bother in cali?) and the water drained out the block and manifolds. sometimes it is hard to tell at an idle but it really shows up at higher rpms when you are missing a cylinder. Sounds more like fuel to me, not a whole lot that can go wrong in a mercruiser thunderbolt electronic ignition... the module on the back controls the advance, if you take the cap off you should be able to turn the rotor and shaft a slight bit, make sure it is free and when you let go it returns to its neutral position. with as much voltage as it puts out even a dirty cap and rotor won't significantly slow you down, usually they run or don't (electronics good.. electronics bad)... and if it was ignition you;d likely hear the motor breaking up at higher RPM. If you want to check the ignition advance you'll need a timing light and a piece of white chalk or paint stick. mark the notch on the harmonic balancer and clip the timing light lead on the #1 plug wire... you need an adjustable light for this.. with the knob to offset the strobe... you run the motor up to say 3000 rpm, point the light at the balancer and turn the knob from zero upward until the pointer and mark on the balancer line up... the number on the dial is your total timing advance at that RPM. otherwise you can go and buy a timing tape and apply it to the balancer. that motor should have a total of about 32 degrees +/- 1.5 by 3000 rpm or so with initial timing set at 8 degrees at idle if my memory serves me right. hope you figure it out...

Jamie

[RickR]

Sorry! I missed it was a Merc. Does ot have Thunderbolt ignition (black box on side of distributor)? What year is it?
Is the idle OK?

What kind of Carburator does it have?
If is gummed up try spraying carb cleaner in the small orifices near the carb barrels. DON'T LOOK DOWN THE CARB WHILE ENGINE IS RUNNING!

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RICKR
mailto:riggerb@aol.comriggerb@aol.com</A>

[This message has been edited by RickR (edited 05-21-2001).]