Mercruiser 3.0 Stalling When Giving Gas in Forward Gear

[outgoingjake]

Hi all,

Mercruiser 3.0 in a 1987 Rinker. In the water it will idle great, even in forward gear or reverse. Throttling up in reverse causes no issues. Throw it in forward at idle, will still run and move the boat forward. Give it ANY gas at all, and it dies. Will also go through the entire RPM range in the water at idle with no issues.

-Carb rebuilt at least 3 times in the past 2 months, also used identical spare carb to no avail
-Fuel pump replaced
-Spark Plugs replaced
-Condenser replaced
-Points set & filed (nice blue spark)

I've checked the gas in the bowl and there is no water. It isn't old gas. Really at a loss here, and hoping some knowledge sharing will prove useful. Thanks in advance!

 

[RaceCarRich]

I suspect fuel issue. When I had a 3.0L, one time I had to reverse back to the dock to buy a new fuel filter. Changed clogged filter and went back out without issue. Less load on prop in reverse I suppose.

 

[outgoingjake]

I suspect fuel issue. When I had a 3.0L, one time I had to reverse back to the dock to buy a new fuel filter. Changed clogged filter and went back out without issue. Less load on prop in reverse I suppose.

I only have the little filter in the carb and the filter at the mechanical pump, both of which have been replaced trying to fix this problem.

It definitely seems like a fuel issue, but I'm just not sure that would only cause an issue when throttling up in forward gear. I do see what you are saying about the load difference, though. Any other ideas besides the filters?

 

[RaceCarRich]

Not really. Fuel tank vent issues usually run okay at first but and then get worse. Could check to be certain.

 

[dubs283]

is the shift interrupt switch hanging up when throttling in FWD?

 

[Scott06]

is the shift interrupt switch hanging up when throttling in FWD?

This x2 test by disconnecting, but you wont be able to get it out of gear without shutting off the engine…

 

[outgoingjake]

is the shift interrupt switch hanging up when throttling in FWD?

This x2 test by disconnecting, but you wont be able to get it out of gear without shutting off the engine…

My original thought was that the shift interrupt switch, when malfunctioning, would cause issues going into gear at all. I'll have my brother shift it into gear and start giving it throttle while I watch the switch. Will it react the same on land as it would in the water?

Thank you for the help.

 

[Bondo]

The shift switch should activate, Only when comin' Outa gear, 'n only in the water,....

 

[outgoingjake]

The shift switch should activate, Only when comin' Outa gear, 'n only in the water,....

So probably not my issue. Any other ideas? I’m going to check the pickup tube for any blockages, but I’m not sure I’ll find anything.

 

[outgoingjake]

I checked out the switch interrupt and it is operating properly. Also checked the pickup tube, and the tank looks very clean. On land, it will go into forward and rev up as well, so it’s definitely related to the extra load put on the boat while in the lake. I’m not even sure of what to try next.

 

[Benny67]

Hi all,

Mercruiser 3.0 in a 1987 Rinker. In the water it will idle great, even in forward gear or reverse. Throttling up in reverse causes no issues. Throw it in forward at idle, will still run and move the boat forward. Give it ANY gas at all, and it dies. Will also go through the entire RPM range in the water at idle with no issues.

-Carb rebuilt at least 3 times in the past 2 months, also used identical spare carb to no avail
-Fuel pump replaced
-Spark Plugs replaced
-Condenser replaced
-Points set & filed (nice blue spark)

I've checked the gas in the bowl and there is no water. It isn't old gas. Really at a loss here, and hoping some knowledge sharing will prove useful. Thanks in advance!

Shift interrupt switch is killing it when you push it forward. Check the shift adjustment .

 

[nola mike]

I checked out the switch interrupt and it is operating properly.

Meaning it's not closing when you throttle up in the water? Agree that this sounds like the issue.