1989 MerCruiser 330 falls on its face sometimes

B

BillWilliams

Member
Member
Joined
Jan 1, 2000
RO Number
2904
Messages
279
We have a 1989 MerCruiser 330 (454 cid) with a Bravo I in our Sea Ray. Most of the time, everything runs fine but occasionally when first coming out of the hole, the engine will just about quit as if it's not getting enough fuel. We'll pull back on the throttle and then hit it again and it will take off. Once up on plane, the engine runs fine right up to WOT if I want to.

I have been thinking about the accelerator pump but I would think this behavior would be much more consistent if it were that. Also thought it if were plugged fuel filters or the fuel pump, the engine would not run at the higher RPM.

Any suggestions?

Thanks
 
Perhaps timing or idle mix adjustment ? When was the last full tune-up? A vac gauge test may help reveal the problem source.
 
It's been a few years since a full tune-up with cap, rotor, wires, etc.

It's very strange because it will run fine and then suddenly take to having these "fits" and then go right back to normal.

I've purchased a carburetor rebuild kit but I really don't want to tear into it if it's not necessary.
 
Suggesting new properly-gapped plugs, cap & rotor , confirm correct timing , maybe ohm-out the cables to look for anomalies, then if the problem persists maybe temporarily plumb in a portable tank with fresh gas and label-recommended portion of Sea Foam.

Kindly let us know what the plugs and dist. parts look like.
 
could be float level low or float valve sticky.
 
Charlie: wouldn't float being too low cause flooding not insufficient fuel

I always recommend starting with the simple stuff such as filters and fuel pickup, tank vent, loose wires etc
 
Replace the fuel/water separator every year. I also replaced the fuel filter in the carburator this spring. I'm trying to start with the simple stuff too.
 
Also check the anti-siphon valve coming out of the gas tank
 
Bruce, Float level indicates how much fuel is available. Also can affect fuel/air mixture. Too high makes it too rich. Too low means too lean...usually caused by float needle getting stuck at the bottom, cutting off fuel supply. When enuff pressure from weight of float lifts the valve off the seat, fuel can flow again.
 
I'll also throw in, if any of the fuel fill ,vent and distribution lines are original 1989 and you use E10 gasohol they are likely in bad shape and could be delaminating internally , cracked, swollen or porous. I believe the year should be printed on a full length stripe, and it would also indicate "alcohol-resistant" if updated. None are alcohol-proof.
 
I've been looking around at my orders and last full tune-up was back in the spring of '04 (time flies). I believe that's going on my list as well.
 
Humm. Long time since I had a carb apart. Back then floats raised to close needle valve lowered to open. Sinking floats allowed flooding. Worked just like toilet float valves.

I don't know nothing any more. :(
 
Bruce, you got it exactly right. Think it thru. Th needle is attached by a wire that allows some movement. So, when the engine uses fuel, the float lowers, pulling the valve off it's seat and allows fuel into float bowl. A sticky valve won't release from the seat and in rare cases can hold the float off the bottom. When something like that happens, the engine runs out of gas and if the throttle is open you'll get a lean pop just before it runs out of gas.
 
Got the tune up parts. Probably install this weekend but have to wait until next weekend at the earliest to try it. Everyone, thanks for the suggestions.
 
Well, did the tune up and so far the engine is running fine (but it does that 90% of the time anyway:)). We'll see how things go.

Thanks for all of the suggestions.
 
Charlie, yes the problem would happen during hard acceleration getting up on plane. Since the tune up, haven't had the issue but it was intermittent to begin with so we'll see.
 
You must log in or register to reply here.
Back
Top