Ventilation/Cavitation Problem?

[richardg]

I have a new 18" Fiesta with a 50 hp Mercury 2 stroke, long shaft. I am having a problem
with what I believe is a ventilation problem. Any small disturbance in the water, i.e., small wake from a passing boat, running with the current will cause the boat to lose power and RPM's to increase. It appears that the prop has come out of the water. This happens regardless of where motor is trimmed and has happened with only me on the boat. The only time I have not had this problem was with the boat loaded with people, lots of weight aft.

I have done a bit of research and I am beginning to think that this particular motor is not a good fit. Does anyone have an opinion on whether or not this should have been a Bigfoot or something similar with a bigger gearcase and prop? Also, I believe the bigfoot sits lower in the water.

I know this is a stretch, but the dealer has had it back twice and says it runs perfectly for them. The only difference is they run it in a fresh water lake and I use it in saltwater in protected waters near Tampa Bay. Since boats may sit higher in saltwater is it possible that even a small difference vs. fresh water could make enough of a difference for the prop to lose its bite?

Any and all thoughts would be appreciated.

[lakerunner]

Where is your anti-cavitation plate on motor in reference to bottom of motor transom? If it is above can it be lowered? If not I would think you need the X long shaft.

[LiquidSunshine]

This sounds like the problem that we had with our Mercury 50 hp 2 stroke on a 21' Suntracker-it took MONTHS for the dealer to re-create the problem and finally I was able to re-create the problem by messing with the throttle and trim. It turned out that the battery cables that were put on by the manufacturer were too short. I'm not sure if this is your problem but after they put new cables on, we never had the problem again.

[lakerunner]

How does a short battery cable effect cavitation ???

[cwag911]

I'm with you Loyd. ???

[badmoonrising]

Thirded