carb seems to be giving out at high speeds

[kevdon]

Thank you all in advance for taking your time out to help me solve this issue. I have an 85 v that is powered by a 4cyl mercruser 170. the last 2 times out the boat has tried to quit running when i got up to about 15 knots.It starts right back up and runs fine at a lower speed.Whats got me is after it happened initially I thought I was low on fuel and the plane of accelerating was causing me to not get proper fuel.But tonite when we went out I put in 15 gallons of gas and a bottle of fuel injection cleaner.Boat ran fine at all speeds for 1st hour than same probs occured.I had new carb installed last season and have had no previous problem until now.I have mercruiser repair manual and it suggests running a few tests that require pressure gauges and such.I am hopin for an easy fix.Could the fuel filter be the reason even know it runs fine at lower speeds and starts up on a dime.I am wide open for feedback.Thanks all !!

[Rod Mulhall]

Originally Posted by kevdon

Thank you all in advance for taking your time out to help me solve this issue. I have an 85 v that is powered by a 4cyl mercruser 170. the last 2 times out the boat has tried to quit running when i got up to about 15 knots.It starts right back up and runs fine at a lower speed.Whats got me is after it happened initially I thought I was low on fuel and the plane of accelerating was causing me to not get proper fuel.But tonite when we went out I put in 15 gallons of gas and a bottle of fuel injection cleaner.Boat ran fine at all speeds for 1st hour than same probs occured.I had new carb installed last season and have had no previous problem until now.I have mercruiser repair manual and it suggests running a few tests that require pressure gauges and such.I am hopin for an easy fix.Could the fuel filter be the reason even know it runs fine at lower speeds and starts up on a dime.I am wide open for feedback.Thanks all !!

I would most definately check the filter! What I have done in the past, is run the motor off of a 6 gallon outboard tank full of FRESH gas, bypassing the filter. With this ethenol gas nowadays, no telling what is happening! Look into buying STAR TRON. It is supposed to help with the ethenol.
Good luck, Rod

[kull79]

If you are getting gas at a station with ethenol try finding a station that doesn't have ethenol gas. Secondaly check the ignition system.

[nymack66]

Process of elimination connect a portable tank bypassing the filter and most of your fuel lines, test if all is well you now know where your problem is.
Replacement of a filter is always a good option if fuel contamination is present like water ..

[Rich P]

Sounds like fuel filter but could be other things as well. Change the fuel filter(s) since it is a relatively simple thing to do and probably needs to be done anyway. Find the drian plug on the bottom of each carb and open them up (do not drop the plugs) to let whatever is in the float bowl out and then use the primer bulb to shoot a little clean gas through there. Replace plugs and when there is no more gas fumes take her for a spin. If problem persists, you might need to disassemble and clean the carbs, might have a coil that is malfunctioning when hot, or might have a fuel vent restriction. Good luck.
-Rich

[spareparts]

use the portable tank idea after you've eliminated the fual filter. If you use an old outboard tank, keep the primer bulb in line for testing, see if it acts up, the squeeze the bulb and see if it gets betetr. there is also a fule filter made onto teh fuel pump, its under the dome looking thing on the fuel pump, you'll see a screw thats safety wired in place, looses teh screw, remove the strap over teh dome, adn pull the filter out, Odds are, its never been replaced. If you need local help, I know several good shops around there. In case you haven't allready done it, I recomend replacing the points with a pertronix conversion kit, it will save you a lot of headaches