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THanks to all you experienced vista owners for you answers to my questions! So here is another.

I posted briefly about this previously and got no suggestions...have some more details.

I have put about 10 hours on my Volvo Penta Inboard engines and I have noticed this issue twice. Both instances it acted the same. I am at cruising speed and all the sudden the port engine loses power. It drops to about 1K RPM and then proceeds to rev up to about 2500 and back to 1000 in just a few seconds and over and over again. During this time there is absolutely no throttle control on this engine. It is doing what it wants. All guages look normal. Other engine normal.

Seems to reset itself after turning off engine for several minutes. Took a couple of tries this last time but then it seemed to be normal.

In the first instance, I was using Sync. I initially suspected it was electrical related because of the way there was no throttle control and because it reset after shutdown. I have not used Sync since, putting several hours on the engines with no issues.

Then it happened again yesterday when I wasn't using sync. My wife noticed that both times it happened I had just gotten gas and those were the only 2 times I have gotten gas.

Could this somehow be the cause? Could there be some water or something in my port tank that the fillup stirs up? I could see that causing loss of power or stalling but not the reving. And why would it go away after shutting the engine down?

Any ideas would be appreciated.

Sounds exactly like the problem I was having on my boat when it had bad gas. It would rev itself up and down and if I gave it throttle it would flood the engine and shutdown. I changed the water separator, drained the fuel, cleaned the fuel tank, and I am using Non ethanol fuel now and the problem hasn't resurfaced. Good luck trying to get to the bottom of your problem.

Yes, it does sound like bad gas, or contaminates in the fuel/filter, when the fuel is restricted(dirty filter) it will lean out the motor which in turn will increase the RPM and if fuel is not introduced to the system in time it will stall, you do not have to touch the throttle for a lean condition to increase the RPM, unlike an electrical issue which will normally cause the engine to cut out and come back or not RPM high enough. When the contaminates settle away fom the inlet of the filter the engine will act normally again until the restriction comes back (like a clogged vaccum filter/hose).

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2000 H190 5.0GL

SOLVED.
As my mechanic stood in my engine compartment, I described this issue he immediately turned around and checked the fuel filters and they were finger tight at best. Easily unscrewed. He said, this happens all the time because most mechanics are lazy and don't get out the wrench to tighten them. They loose their seal easily when loose.

No more issues.