Engine miss when under load.

[chiefalen]

Re: Engine miss when under load.

Keep her close to shore for the first couple times out. You checked the outdrive oil and changed it.

Good luck and g-d bless.

 

[Fishstick]

Re: Engine miss when under load.

Keep her close to shore for the first couple times out. You checked the outdrive oil and changed it.

Good luck and g-d bless.

Yup, drained it today and checked....no water or metal, nice and clean. replaced with fresh. Was gonna do the engine but I'm gonna need to purchase a pump to pull it from the top. Pretty tight in the bilge. My mechanic friend is going with me on his boat just in case.

 

[Fishstick]

Re: Engine miss when under load.

Update:

Dropped it in the water today......No joy, intermittent miss at idle now and when you put the throttle to it, it spits-backfires and dies. New fuel today as well. The only thing I havn't done as of yet is tear the carb down. Thoughts?

 

[Don S]

Re: Engine miss when under load.

Could be the carb, or the fuel delivery system to the engine.
Look up in the Adults only sticky and read the How to test your boats fuel system.
An air leak or clog somewhere could be causing the problem.
A quick workaround test to quickly narrow down the prospects is to run the engine an an outboard tank hooked directly to the engine.

 

[Fishstick]

Re: Engine miss when under load.

Thanks Don.

 

[chiefalen]

Re: Engine miss when under load.

Check out post 17 to this thread. Didn't do any of it did you ???

 

[Fishstick]

Re: Engine miss when under load.

I sprayed some carb cleaner in the carb, but didn't take it apart at all. I cleaned the fuel filter at the carb, which was dirty. Drained the main tank and replaced with fresh fuel and a can of sea foam. Don't know enough about the fuel pump to start messing around with it yet. Didn't do the connecters, so you got me on that one.

 

[chiefalen]

Re: Engine miss when under load.

Take the carb apart and clean every single hole. The smallest are the ones that get ya.

Backfire is usually timing related.

The carb kit is like 15 bucks, and latter for that sea foam stuff i don't use it, get a can of carb cleaner and take apart the carb and clean it good with the cleaner and compressed air.

Put it back on the boat and post the result after you run it.

Bring the guy again with you and maybe he will have to adjust the timing while your running, maybe someone rebuilt this motor and didn't use the spec cam, or crank who knows.

 

[Fishstick]

Re: Engine miss when under load.

copy that.....thanks. Will post again next week.

 

[Fishstick]

Re: Engine miss when under load.

Update:

Today I hit the carb (kit in hand) and the carb is (WAS) dirty. I came across something strange when I got down to the venturi cluster. According to the exploded view that I have (came with the kit) there is supposed to be two "main well inserts" (labeled as #61 on the exploded view) under the cluster. Well, there ain't no inserts.....the guide, spring & ball are where they are supposed to be.....but no main well inserts. My work area is clean, organized and the bowl assembly was upright so I know I didn't drop anything. (Note: the carb is a rochester 2bbl #17059059) The exploded view is general and notes it will vary to individual units.........

If the previous owner rebuilt this carb and forgot them, could this be the problem or perhaps there are no inserts for this particular carb?? Any input appreciated.....

 

[JustJason]

Re: Engine miss when under load.

if i'm thinking of what i'm thinking of (no picture in front of me) those "inserts" are pressed into the discharge nozzles that you unscrewed through the carb.

 

[dan t.]

Re: Engine miss when under load.

these are a plastic tube affair with a guide piece down one side, some carbs have them ,some dont, I dont know the reason if you can find an oem parts break down it should tell you, get an ohm meter and check your plug wires, a high resistance will make it miss under load,or a cracked plug porcilane, try running in the dark to arcs to ground
good luck

 

[Fishstick]

Re: Engine miss when under load.

these are a plastic tube affair with a guide piece down one side, some carbs have them ,some dont, I dont know the reason if you can find an oem parts break down it should tell you, get an ohm meter and check your plug wires, a high resistance will make it miss under load,or a cracked plug porcilane, try running in the dark to arcs to ground
good luck

Thanks Dan. The wires & plugs are new; however, that doesn't mean anything these days. I never thought of running it at night to check for arcing, I'll give it a try. I'll research further on the inserts for my particular carb. To many variables in the kits and documentation they send with them. The kit I did get fit numerous models of carbs.....with one exploded view.

 

[dan t.]

Re: Engine miss when under load.

ok I just looked in my 1996 oem merc manual at a 2bbl rochester parts breakdown, it doesnt show any main well inserts,hope this helps

 

[Fishstick]

Re: Engine miss when under load.

ok I just looked in my 1996 oem merc manual at a 2bbl rochester parts breakdown, it doesnt show any main well inserts,hope this helps

Yes it does and thank you.

 

[CharlieB]

Re: Engine miss when under load.

Did your carb kit come with an accelerator pump plunger?

If Not then see our parts man and get one.

A stumble/cough/sneeze on acceleration is often a sign of a faulty accel pump shot causing the carb to go lean during acceleration, pulling back on the throttle to match the current engine RPM stops the miss and the engine smooths out.

 

[Fishstick]

Re: Engine miss when under load.

Did your carb kit come with an accelerator pump plunger?

If Not then see our parts man and get one.

A stumble/cough/sneeze on acceleration is often a sign of a faulty accel pump shot causing the carb to go lean during acceleration, pulling back on the throttle to match the current engine RPM stops the miss and the engine smooths out.

Yes it did, new plunger, ball, spring, gaskets, etc. The carb is back on the boat and I'll fire her up tmrw if the rain gives me a break. I'll post the results when I can get her back on the water for a test run......Thanks.

On the bright side of things, as I go through both the fuel and electrical systems one piece at a time, I'm learning much about this boat and the knowledge gleaned from members of this forum and that hands on experience is priceless.....thanks to all

 

[Fishstick]

Re: Engine miss when under load.

Update: Wind blowing like crazy so no on the lake test today; however, put the carb back on and after a couple of adjustments, the throttle response is much better (from what I can tell on the muffs without over rev).........but, that "miss" is still there and now I'm not actually sure it is an engine miss.

I got my redneck stethascope down there and listened to the cylinders/block/valve covers etc. When it misses, it's more of a "clunk" sound and most pronounced around the stern, flywheel area. I hopped out and wrapped my hands around the upper gear housing in the drive and when it clunks, you can feel it in the drive. The exhaust "spits" which is why I initially thought it was a miss. I also noticed that when it does "clunk" the engine revs for a slit second then levels out. It does this in both neutral and in gear. What would the typical symptomology of a bad u-joint in the drive be?

In any event, it's going downtown to the pro's for a diagnosis. I just want to make sure I give him all the information I can.....