1997 mercruiser losing power (not stalling just surgeing) @ 1600 rpm - 3000 rpm.

[LB MATT]

Where would be good place to start?

 

[alldodge]

Where would be good place to start?

Need more info.... but fuel pump pressure, fuel filter, anti siphon valve and carb

and :welcome: to iboats

 

[LB MATT]

I am new to engines but I am very mechanical inclined so try to bare with me.(long story long) When we were out the boat would surge around 2600 rpm and would die when coming to a stop. We got home let it sit for a couple of weeks, tried to start and it would not stay running. So we rebuilt the carb. Now it stays running but the surging is now between 1600 - 3200. You are saying to obviously 1. check fuel pressure. 2. Change the fuel filter and check the anti siphon valve. How do you check fuel pressure and what is the anti siphon valves function.

 

[alldodge]

I am new to engines but I am very mechanical inclined so try to bare with me.(long story long) When we were out the boat would surge around 2600 rpm and would die when coming to a stop. We got home let it sit for a couple of weeks, tried to start and it would not stay running. So we rebuilt the carb. Now it stays running but the surging is now between 1600 - 3200. You are saying to obviously 1. check fuel pressure. 2. Change the fuel filter and check the anti siphon valve. How do you check fuel pressure and what is the anti siphon valves function.

Still could use more info about what we are working on, such as is this a V8, 6 or 4 cylinder.

To test fuel pump pressure you put a tee fitting inline between the fuel pump and the carb. Connect a vacuum/fuel pump test gauge inline such as the one in the link below.
http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html

The anti-siphon valve is connected directly to the tank and looks like a barbed fitting which your fuel line is connected. There is a metal ball and spring inside the fitting and it keeps fuel from being siphoned out of the tank and into the boat if the fuel line brakes. It can get stuck and cause issues with the pump being able to suck fuel from the tank.
http://www.iboats.com/Moeller-Aluminum-Anti-Siphon-Valve/dm/view_id.392106

 

[LB MATT]

Thanks and sorry, It is a 1997 5.7 Mercruiser. V8

 

[LB MATT]

What pressure should the fuel be at? If the fuel pressure is good, does this mean the anti-siphon valve is working?

 

[LB MATT]

What pressure should the fuel be at? If the fuel pressure is good, does this mean the anti-siphon valve is working?

 

[alldodge]

What pressure should the fuel be at? If the fuel pressure is good, does this mean the anti-siphon valve is working?

Sorry missed telling you the pressure, it should be between 4 to 7 psi. If the psi is good, the anti-siphon valve could still be an issue but before you check it do the other things mentioned previously. Hope something should show up

 

[IdahoDoug]

I am 95% sure I read in researching my own issue that on the 5.7 of your year if an engine surges to replace the spark plugs. I was a known issue enough to be discussed in the MerCruiser literature. I don't know the connection (tiny misfire might fire off the knock sensor, etc?) but I'm quite sure I saw that for the 5.7. Mine is a 1997 7.4 so I ran through a lot of stuff for both engines.

DougM

 

[LB MATT]

Thanks for the feed back. I will try that as well.

 

[Maclin]

Carbed or Injected? If carbed, 2bbl or 4bbl?