engine dies below 1000 rpm's...

[benjiman]

84' Mercruiser 898 5.7...
While on the water the other day, the engine would die every time I would pull the throttle back below 1100 rpm's. The shift cable hasn't been correctly adjusted since I installed a new one a couple weeks ago and I know that is connected to the kill switch (or whatever it's called). I can start the engine with the throttle partially forward but not at idle anymore. Any suggestions?

 

[Reel Poor]

Re: engine dies below 1000 rpm's...

Has it had a full tune up ? Plugs,wires, cap, rotor, fuel filterS, timming checked (advance also), compression check. Could be the choke flap is not opening. Could be a vaccum leak i.e. carb base gasket, intake manifold gasket, internal carb gasket, carb flooding (not choke related), improperly adjusted air mixture screws.

 

[benjiman]

Re: engine dies below 1000 rpm's...

Yes, new plugs, wires,distributor, water seperator, filter, etc. Where is the choke flap and how do I check it? Where is the air mixture screws? Thanks...

 

[llerrad]

Re: engine dies below 1000 rpm's...

Check your points, dwell and timing.
Correct timing will help maintain low idle.

 

[Reel Poor]

Re: engine dies below 1000 rpm's...

84' Mercruiser 898 5.7...
The shift cable hasn't been correctly adjusted since I installed a new one

And why not. You need to finish that job first and see if it takes care of your problem. Get yourself a manual so you have the information you need to do the repairs. here is a link to a manual for proper shift cable linkage adjustments.

Manual

 

[freddyray21]

Re: engine dies below 1000 rpm's...

I agree adjust the shift cable first. the shift interrupt is supposed to momentarily stall the engine when you pull it out of gear to help it get out of gear. sounds like it it hanging up killing the motor

 

[jerryb1]

Re: engine dies below 1000 rpm's...

I have the exact same problem, so I'm curious to find out what the problem is. From the schematic, it looks like the kill switch momentarily shorts out the points to ground. That should be easy to check with an ohm meter while the engine is off(points disconnected or open of course). I havnt had a chance to check out my boat yet as it just happened , but if I find what the cause is I'll note it to you.

 

[freddyray21]

Re: engine dies below 1000 rpm's...

most of the time when the boat was okay and now it's not in the situation described it is because you need a new lower shift cable. It is binding up causing the shift interrupt to hang and kill the motor or not work at all and you can't get it out of gear.

 

[milkyway]

Re: engine dies below 1000 rpm's...

Disconnect the throttle cable at the carburetor then try to run at idle only. This way you can isolate a throttle problem from the carburetor adjustment. If you can't maintain an idle, then you should first correct the idle speed screw and the air mixture screw.

When the mixtures are already set correctly and you can maintain an idle, then proceed to the cable. Adjust the cable without adjusting the speed screw when you do this.

When these are done and the engine dies when you shift, most likely the interrupt switch.

If you can't maintain an idle with the cable disconnected, as reelpoor stated, it also could be a vaccum leak i.e. carb base gasket, intake manifold gasket, internal carb gasket but work on the easy ones first.