225 v8 1976 omc

"g"day, my boat iddles gre

"g"day, my boat iddles great when I start her up.goe well up to 4000rpm but when I begin to troll I GET TEN TO FIFTEEN MINUTES BEFORE SHE STALLS.STARTS STRAIGHT AWAY THEN STALLS. LET HER SIT A WHILE AND SHE GOES GREAT AGAIN TILL I START TROLLING AGAIN.iS IT TOO MUCH/NOT ENOUGH FUEL,DIRTY FUEL,HOT IDDLE...ETC ?PLEASE ANY HELP IS GREATLY APPRECIATED.THANKS CHRIS"

"Hey Chris,
Is the engine run

"Hey Chris,
Is the engine running at normal temps? Keep a watch that the temp isn't creeping up when you are trolling.
If it runs fine at higher speeds and is heating up at lower speed the impeller could be failing.
On the other hand the low speed fuel circuit my be getting plugged.
Does it idle rough like the choke is on or seem ot be running out of fuel?
You could have a few things going on. The engine could be getting hot causing the fuel to boil in the fuel line or float bowl(running vapor loc) the carb is dirty or the filters. Vacuum leaking at the intake or base of the carburetor. If the ignition system is a points model check the condition of the points.
I doubt the fuel pump is bad if it will run at higher speeds.
If you do not know the last time the water pump was serviced it would be a good thing to check.
The thermostat my be sticking also if the engine is heating but pumping water.
Whatever the problem is it doesn't sound real bad.
There is alot of problems with fuel and heat this season.
Not only are our good friends at the oil companies make something like 8 million an hour selling fuel but the gas is crap.
If everything checks out and you are still having problems(I hate to say this) try a better grade of fuel.
Make sure there is good air flow under the engine cover. I'm sure there can be other things that will cause this but this is a good start."

"thanks charli,
changed fuel

"thanks charli,
changed fuel filter and lots of crud from tank.cleanning tank sunday.mayby not enough fuel when going slow.putting sea foam through fuel and car spray through intake.temp does go up by 5 degrees when trolling.mayby impeller needs changing.sat for four years not running.
thanks for reply."