Mercruiser 898 cutting out

[kmongar]

Boat: 1980 Pursuit, 898, originally 305 now 350, stock intake and 2 bbl carb

Problem: The boat starts easily and runs well for about an hour. Then when cruising (3000 to 4000 rpms) it just cuts out and dies. No sputtering, knocking, backfiring or anything. Starts right back up and will run at low rpms. Try to 'cruise' again and cuts out again. When this happens the temp gauge says about 150 degrees. Oil pressure seems high at 75 to 80 on gauge. Volts are at 13.

Stuff I have tried: I replaced the OEM distributor with a Mallory breakerless. new cap, rotor and plugs, new coil, changed oil/filter, new water/fuel filter, checked fuel filter at carb...seemed clean, timing is at 8 BTDC at 600rpm. After doing all that it seemed to run extremely well for 1 or 1 1/2 hours until...it it did the same thing.

Any advice would be most appreciated.

 

[Haut Medoc]

Re: Mercruiser 898 cutting out

Have you tried running it with the cap off the gas tank when it happens?....
Possibly a blocked tank vent......
You are getting starved for fuel somehow.....
Welcome to iboats, btw......​

 

[kmongar]

Re: Mercruiser 898 cutting out

Thanks for the welcome. I'm sure I will be a frequent flyer.

Have not tried the cap trick. I have seen several other threads that talk about similar problems possibly caused by a plugged vent. I never thought about that before today but it makes sense. I'll disconnect the vent line from the tank and see if I can blow through it.
thanks for the suggestion

 

[kmongar]

Re: Mercruiser 898 cutting out

Back again.

I took the vent line off at the tank...and could easily blow through it to the outside vent. Is it possible that it is obstructed inside the tank? Fyi. I don't have any problem refueling.

Other info: I took several of the 'new' spark plugs out. The motor had only been run for about 2 hours with these new plugs. They were already sooted up...black...and were 'wet' when removed (after idling in the driveway). I checked the idle mixture screws on the carb. They were out about 3 turns. I re-adjusted starting at 1 1/4 turns out and wound up right about there for the final setting. Could this just have been a plug fouling problem?

 

[Haut Medoc]

Re: Mercruiser 898 cutting out

I doubt it.......
I still think you have a fuel delivery issue.....
Plugged fuel pick up screen, anti-siphon valve, carb screen....
Sounds like you've gone though some of it.....
I'd check the water separater again.......​

 

[Don S]

Re: Mercruiser 898 cutting out

Try this:
http://forums.iboats.com/showthread.php?t=167561