rkeith01

Help..potentially alarming issues
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In the past week I have come up on a couple of different things that seem to be somewhat alarming to me. Not sure if these are normal or not so I thought that I'd ask and see if anyone has any insight on what might be going on here.

Power -> 1998->454Mag(stock)->~370hrs

1. When cruising to a spot to hang out running ~3200 rpms for about 10 min or so, when i powered down to idle I recieved an alarming sensation from the motor, much like what you would feel in a car that spark knocks after you turn it off. Did not put it neutral powered back up and went back home (did not want to get stuck out there). But when I got back to the dock powered down in no wake zone and docked not sensation. Should this be alarming? Maybe some bad gas, but I haven't filled up in about a month or so??

2. When running at WOT the tach reads above 5200 rpm some times. I would think that the rev limiter would prevent this. Maybe the tach needs to be recalibarated?? Or some thing else??

Thanks in advance for any help here..

Wobble

Best way to check tach is with another tach or a digital timing light with rpm readout. If they agree at 3000 or 4000 in neutral I wouldn't worry about the occasional off reading.


Re: stumble. If you have not serviced motor recently now would be good time. Plugs, cap, rotor, fuel filter and separator.

Check for vacuum leak around carb base intake manifold just to be safe.

Hard to say what else unless you can duplicate problem. Your motor can run on 87 octane, I beleive, and 1 month old gas should not be an issue.

Wobble

I'm assuming all your guages were reading normal.

rkeith01

Wobble - hey thanks for the help here...

Yeah, all guages that I have (oil pressure, temp & voltage) were reading normal. I've changed the plugs, cap, rotor, fuel filter/seperator at the beginning of this year. That's what kind of worried me. I'll check the vacuum tube, I tried to replace out the stock flame arrestor with an aftermarket K&N but the fitting on the K&N was stripped for the vacuum tube fitting so I put back on the stock one. Perhaps I did not attach the vacuum hose tightly enough??? Just A little odd and somewhat scarey as this is my first boat, and it being used too...

Wobble

I think you are referring to the crankcase vent hose that comes from your valve cover to the flame arrester. This should not be an issue.

Is your idle rpm normal?

rkeith01

Yeah, seems normal ~ 1k rpm. But the freaky thing is it only did it when I powered down from running, which freaked me out and did want to be stranded so powered back up to go home and it didn't do it again, well so far need to get it back out and check it over some more. wife said it was just a fluke thing....hmm..do you think it might be a fluke thing??

Thanks again for all your help...

rkeith01

hmm....where does one get 99% isopropyl alcohol?

Thanks again for all help here...

Griff

otherwise known as heet or rubbing alcohol.

I doubt h20 in the fuel is the problem though. Your water sep filter should catch it and would have to be full of water. If this happens it runs like chit if at all.

With regard to the rev limiter, what igntion do you have??? TB IV or TB V???? Is it a carbed engine???

TB IV's don't have limiters on black engines