1989 25HP Carb rebuild

Rebuild is for a idle issue, it won't stay running in neutral.
Compression 90 on both, good blue spark on both.

OK I got the kit, and disassembled everything. It all looks OK.
The only possible issue I see is the fuel pump gasket is not as tight as the new one.
Metal parts are soaking overnight.

I removed the Seat (46) and Retainer (45). Was that a bad idea?
They are in the kit. Seloc manual shows them, but says nothing about them.
Which way does the seat go in? There is a groove in one end of it. (Tiny red part in the primer assy.)

Low speed needle was out 2 1/4 turns. Is that normal?

There is no gasket sealant anywhere, is this normal for Mercury motors?

Thanks again all!
Jim

OK all done. Much better but not perfect.
I adjusted that wire Jeff mentioned, and played a little with the low speed needle.
I think it is ready for a boat test.
It idled for several minutes before stalling.
And it will now go from in gear to neutral without stalling.

OK, I do need some help.
It will run for about a minute in the tank, then you need to pump the bulb.
I think it is a timing issue or the float is adjusted wrong?

The throttle cam marks do not line up with the roller at idle. (It was that way when I got it.)
If I make them align, (with the spark advance link rod) it really won't start, and if I can get it to start it idles so low it won't stay running.
I think I need a timing light and a tach.
The first problem then is going to be I need it at WOT and I can't do that in the tank.

What is the function of the "dashpot"?

Also, could a missing or stuck thermostat be an issue. I had it running a long time, and nothing got close to warm except the water coming out of the telltale. It was only slightly warm. Head and exhaust cover were cool/cold.

Also I got a healthy zap off of one of the spark plug wires through the insulation. (Issue or not?)


Any help would be appreciated.

Thanks

Jim

If you have to pump the bulb then that clearly points to a fuel pump problem or a crankcase compression problem.-----Crankcase pulses is what drives the fuel pump.----A cylinder compression test is a good idea here.-Crankcase compression is harder to test / diagnose.------The dashpot is there to keep throttle open slightly when you slow down suddenly.--------These motors do dot like a rapid shutoff of the throttle.

89 top and 89 bottom.

OK what do you suggest? Tear apart the carb again?
Anything I should pay really close attention to in there?
I did raise up the tank over the engine, and it ran a long time.
With the tank on he ground you have about 45 seconds.

Could timing off cause lower crankcase pressure?

One curious thing, when I unplugged the fuel line when I was done to let it run out of fuel, the idle increased just before it ran out of gas instead of the slowing down/stalling symptom I am having every 45 seconds or so.

Timing has nothing to do with crankcase pressure.--------------Most motors will speed up ( leaner mix ) just before the carburetor goes empty.

Looks like the carb wasn't the issue after all.

Do I need to replace both sets or just one?

Thanks

I would be willing to bet that reed breakage has something to do with crankcase compression as per post # 4

I sure hope so. I removed them because the hole that goes to the fuel pump was right behind the reed valves.
The broken set was on that side.
Do I need to replace both sets or just the broken set?
Do they just break, or do I need to look for a root cause?

I believe you will have to replace the entire reed block as a unit (about 90 bucks).

There was 2 designs for the 25's of that vintage. One was "modular" the other a complete unit.

The "modular" components are now discontinued, so while you may be able to find some "old stock" (if you have that version - I can't quite tell from your pic if your reed petals are screwed into the block which would give you the modular version), I would do both sides if you can just in case the other side has a fracture that you can't see at this point - otherwise, replace the whole block.

The petals were about 35 bucks a side plus a couple bucks for the stops, so not a whole lot cheaper than the whole shebang anyhow.

As to what causes chipped/broken reeds - save a major crankcase failure with metal parts trying to exit the carb from the back side, the top suspect would be the carb sucking up some type of debris that gets caught by the petal. Then on the piston down stroke the pressure forces the petal against the "junk" chipping the edge of the petal (think of slamming your finger in the car door - the weakest part, your finger (or reed petal) loses that battle...

Update. I thought I would share what else I found.
I got the reeds and was installing the reed block. No problem. Then I put the carb gasket back on the reed block instead of the carb. Good thing I did because I would not have noticed it was the WRONG gasket.

Left is the right one. Middle was the one I put on last week. Right one was as I received it.
Without that oblong hole, the port to the fuel pump was completely blocked.
I almost repeated the problem.
Tank test tomorrow, boat test Sat. hopefully.