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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Alldodge response: Yes, I think that's what I'm saying that the carb is running out of fuel. After about 40 minutes I started revving the engine to simulate more demand on the fuel and the engine started to stall and finally cut off. After that it would not start at all. The other thing I saw...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Not sure how long threads are left up before they expire so here goes. I was finally able to run another test with the motor just in idle between 1000 and 2000 rpm for around 40 minutes. However, it did not begin the loss of power until I quickly advanced the throttle several times. I then...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Pigpenffx response: Thanks for your input. It's uncanny, your symptoms sound exactly like mine. On a side note, did your engine, after a short rest, always start back up and run fine for some period of time before it started to die again? To recap FYI, here are the repairs I've made so far...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    I searched several other forums to see what the function of the TKS temp switch was and I didn't see where its malfunction would cause the issue I'm having. Can you expand on why you think this could be involved? I realize the TKS temp switch reacts to heat and is in play during engine cold...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Regarding replacing parts before determining what the problem is; we did do test and thought we had determined the issue because the boat ran so much better than before the part was replaced. In all cases of parts that were replaced, they needed to anyway because either they had not been...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Holy moly, why is this like trying to find a needle in a haystack? Is this a boat thing? :) Saw this posting while I was composing this response. To be honest I think I replaced the coil because the engine was running rough. The boat has only been experiencing this current issue over the last...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Well I was so confident, after the first seemingly successful sea trial, that we had discovered the fix (replacing the fuel pump) that I didn't have any test equipment in the boat. So, no I wasn't able to check the coil output. I did however go back to my boat repair/maintenance log and...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Well I'm back with the mystery issue. Finally, after hurricanes and NE winds, was able to make my second sea trial. This time stayed relatively close to my dock. We did another test before the sea trial wherein we ran the boat until the problem occurred, about 25 minutes. This time with the...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    alldodge reply: Sorry you had to delete those posts. I didn't realize there are posters that get offended when one shares observations of what is occurring or not occurring during the sea trial. BTW, I don't think I saw a response alldodge to my question about what component could get hot and...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    alldodge reply: thanks for your feedback. What is a gauge feed, where would it be placed online and what indication would it show? And if it's not fuel then what other components, getting hot, could logically cause the loss of power?
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    nola mike reply: doesn't the fuel pickup in the gas tank extend down to the bottom of the tank where water would be since it's heavier than gasoline? That said, and the boat floating in the lift when I start the engine, could the engine be started with fuel left in the water/fuel filter and it...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Thanks for your responses. I replaced the water/fuel filter last September and I just didn't think any water could get into it since the cap outer rubber seal has always been tight in place. But I will remove the filter and dump the contents into a glass bowl to see if there is any significant...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Well the mysterious loss of power is still a mystery. I was finally able to take the boat out for another sea trial since the river and weather here were calmer. Prior to that I was going down the suggested road that the issue may be related to a fuel tank vacuum issue. Since the boat has the...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    FunTimes post reply; I did happen to open the fill cap as part of the vent system discovery. I wasn't sure how it vents until I read the aforementioned thread (see previous link) describing the cap structure. I am going to give the cap a good cleaning. Regarding the last fill up; since my boat...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    I found a good iboats forum thread here that has a clear explanation with pictures on how the combination fill/vent necks work. This might help someone, like me, understand what to look for on this possible issue cause. My concern with the suggested manor of recreating the problem is I could get...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    More good information. Period of time it takes to form a fuel tank vacuum based on fuel level makes sense. I just finished running the boat through its paces on the river for about 15 minutes and it ran flawlessly. Fuel level, best I can tell from the gasoline level console gauge, is between 1/2...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    All good information. However, my dilemma still is, which of the mentioned possible causes would affect the operation/performance from the get-go, meaning engine won't start, engine idles rough, engine will not accelerate, engine starving for fuel, etc. if there was a real issue with them. Can...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    Cyclops222, thanks for the clarification on the oil pressure switch function.; Yes, the engine is carburated and has an electric fuel pump which was replaced in 2019 by a marine repair shop. Please clarify what you mean by the fuel pump "getting tired". Regarding suggestion for testing the fuel...
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    2006 Monterey Boat with a 4.3L Mercruiser TKS Engine S/N 0w354897 Mysterious Loss of Power

    I have a 2006 Monterey boat with a Mercruiser 4.3L TKS engine that after operating under a load for 35 to 40 minutes consistently experiences a gradual loss of power to the point where the engine appears to be starving for gasoline. When this happens, I back the throttle down to just in gear...
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