Mercruiser 4.3 Fuel Issue

[riodecolumbia]

I’m still relatively new to the boating scene, but I’m figuring more and more things out as I go. I have a 1991 Regal Valanti 190 boat with a Mercruiser 4.3L inboard motor in it.

So the motor will work completely fine for like 45 min or so, but after that it begins to experience a problem. The motor will all the sudden drop about 600 rpm or so and then climb back up to where it was at. Sometimes it won’t make it back up to the original rpm it was at, and keep going slowly down until the motor will die. If you wait a bit the motor will usually get started again, but won’t be long before it dies again the same way.

It has a rebuilt carb, and I thought originally the float was getting stuck maybe but the carb is getting plenty of fuel it looks like and seems to be tuned fine. I checked the amount of fuel in the tank, and it has plenty of fuel as well. I replaced the fuel pump with a new one also, but the problem still seems to be occurring. I was thinking that maybe it may be an issue with something bad in the fuel tank itself, but I don’t know.


Any help would be much appreciated!

 

[H20Rat]

What RPM are you at for 45 minutes? Idling?

 

[alldodge]

When it starts dying, stop and get close to the gas cap, then open it up aand listen for air being sucked into the tank. If you hear the air being sucked in, then its the tank vent

If no air is heard, get a 5 gallon gas can and put the gas line in it and connect to the filter. Then run and see if it goes away or not

 

[Bt Doctur]

My goodness that sounds so very familiar, runs at cruise power and then dies off. Wait a bit and it runs again for a short bit at cruise power and dies off again
Get an outboard tank and next time it happens, unhook the boat tank line and connect the remote line and retest
If your problem goes away I might have the answer

 

[Bt Doctur]

https://forums.iboats.com/forum/eng...gines-outdrives/10786273-gas-starvation-ghost

 

[KJM]

if the gas tank trick don't work then check your spark plugs for water. i had a leaking exhaust manifold that caused similar problems. be careful because if its the exhaust manifold it can cause major damage if not replaced