Help needed with engine idle after resting...

[srv_mtka]

I have a 1981 Sea Ray SRV 195 with a 260hp Mercruiser 898 with Alpha One outdrive. This has historically been a great running boat and knew I had carburetor issues. Last fall, and this spring, I had the carb rebuilt and replaced the rotor cap, wires, plugs, air filter, fuel filter and water separator. Thought everything would be smooth! The boat will start up, idle great and accelerate like brand new - trouble comes when I stop for a period (2-3 hours) to fish or swim. When I try to restart, or actually get it started, it will run at 1500+ rpm but will die at idle (shifting into gear). This only happens once I have been out running it...

I've had in 2 different shops this summer but to no avail (runs great when there). I've been out 4 times in a row and it dies every time. If I do get it running it sounds like it is running on half of the cylinders - could it be a fuel pump? Are the symptoms indicative of this?

I love the boat but it needs to be dependable to continue in my life. Thank you ini advance for any and all ideas.

 

[cmount1]

Does the engine eventually clean itself up, In other words after a short time will it start to run normally once you get it restarted?

Check for a possible air leak. Use some carb cleaner and while the engine is running at idle squirt all of the mating flanges, carb to intake, intake to cylinder head, ect... if it stumbles at any point you found the leak. Also I would check the float level on the carb, if it's set to high and you anchor in rough water fuel could possibly make it's way through the float bowl vent and puddle in the intake, ultimately flooding the engine with excess fuel for the next start. Might explain why the marina can't find it while sitting at the dock. And yes it's worth check the fuel pressure, rig an inline pressure gauge and monitor the pressure. Compare your first cold start to the hot soak start to give a A/B comparison.

 

[moparlvr4406]

sounds like a vapor lock...possible ethanol issue ??

 

[srv_mtka]

moparlvr4406: So, I ran ethanol; through it for the first few years (bought it 2007) but then found a source for non-oxy fuel and switched. How would I prove a vapor lock exists?

cmount1: I am only able to get it restarted once it sits for an extended period. Another scenario I recall while it ran continuously; I drove at 2500 rpm for about 20 minutyes, went through a channel at low idle and when I came out the other side it would not go above 1750 rpm (dogged out). That lasted for another 15 minutes until I got near my marina and then it flat out died. Seems if I alter throttle consistently (e.g. pulling tubers) then no real issue but a consistent throttle for an extended period followed by idle causes the same issue. In all of these scenarios I can smell gasoline so leads me to believe it is not an air supply issue...

Thanks for any ideas...

 

[srv_mtka]

cmount1: I am only able to get it restarted once it sits for an extended period. Another scenario I recall while it ran continuously; I drove at 2500 rpm for about 20 minutyes, went through a channel at low idle and when I came out the other side it would not go above 1750 rpm (dogged out). That lasted for another 15 minutes until I got near my marina and then it flat out died. Seems if I alter throttle consistently (e.g. pulling tubers) then no real issue but a consistent throttle for an extended period followed by idle causes the same issue. In all of these scenarios I can smell gasoline so leads me to believe it is not an air supply issue...

 

[vandal]

Your problem apears to be with the points in distrubter if it has not been changed to electronic. the ground wire coming out on side with white nylon insulator could be cracked it is a prestolite and parts were gone 20 years ago. find an old merc with box on riser.

 

[Iprof]

It sounds like the coil to me, had a 72 Cobra that did the same thing drive it for a while and then it would die, once the coil cooled it would start and run for a little while and die again.

Ken

 

[moparlvr4406]

the only things required to make an engine run are air,fuel,compression,spark and exhaust.
looks like you need to find which peice of the equation is missing when the condition occurs
I would lean toward fuel or spark.
easiest way to ck for a vapor lock is access the throat of the carb and stroke the throttle and see if the accelerator pump squirts a shot of fuel.
but if it just dies out of the blue my instincts tell me look for a lack of spark to the plugs.

 

[cmount1]

As moparlvr4406 said, it's a process of elimination. I do like Iprof's suggestion of a coil, I've seen overheated coils act this way as well. You need to be prepared to walk through the variety of possibilities once the condition arises again.


1) Check the fuel pressure (Gage already installed)

2) Pump the carb once while watching for fuel to squirt from the accelerator pump nozzle

3) Check spark at the coil

4) Check spark at the plug

Each step above will lead you to the next series of eliminations that have to be proved out based on your findings. I know this is a broad stroke but, you have to start at the beginning to find out what part of the equation is missing.

Spk, fuel, air, compression...

 

[Yagamo]

Does your temp gauge vary when problem occurs ? If temp inceases could be restricted cooling issue. I agree with all posts about what should be tested. Sound very much like a coil issue. I have used pertronics ign. modules in industrial equipment and have had a couple act like this also.