assistance please 850 merc.

long story short...
I swapped all the parts from my blown>75>850 onto a good (74 >850) as it had been sitting for some years. my old 850 had a rebuild 2yrs ago and had new CDI ignition, dist. pu, wiring harness, timing belt, rebuilt carbs, fuel pump, all new hosed and rebuilt fuel pump.

I used the Solec book and did the swap of all parts. put the boat in the water and it started fine and ran fine at idle and up to the point where the carbs start to kick in, DOA, engine just dies at that point. will re-start no problem. If you try to ease into the throttle it will start to slobber and miss then die if you go any farther into the throttle.
Did a tear down of the carbs and blew out and sprayed all passages (the carbs were clean as could be) new needle and seats and gaskets. .
Compression was 135 to 140 on the replacement engine and all the filters were replaced, even hooked up my kicker can with fresh gas, no change.

back to the water and same problem.

side note: checked the new plugs and the upper two were wet, the lower two were dry...
any ideas..

thanks Stormmn

Re: assistance please 850 merc.

Well since your top 2 plugs were wet, that would indicate that they are not firing.

Got yourself a spark tester and verify you have spark.

If you don't, then start by checking for a loose wire.

Then try swapping the top 2 coils with the bottom 2.
If you still have no spark in the top 2 holes, then try swapping the inputs and outputs on the pack of the top cylinders with the bottom 2.

If the problem persists, then you have a bad trigger.

If the problem moves to the bottom 2 holes, then you have a bad pack.

Re: assistance please 850 merc.

this engine does not have coils, it has a CDI switch box/coil and all plugs are getting fire as I tested the output with a spark tester before putting into service...

Re: assistance please 850 merc.

since you said the motor had been sitting for some time, maybe one of the fuel pump diaphrams has a hole in it letting raw fuel in the top of the engine. Did you have any backfires at startup? Backfires are notorious for rupturing pump rubber.

Re: assistance please 850 merc.

I'm no expert, but I would say on a 2 stroke, the two wet plugs are "normal" and the two dry are not "normal". While underway, I would try to spray some gas into the bottom carb and see if it picks up. I would say you are starving for fuel. Reeds? I don't know, still seems like a plugged up carb, ie, main jet.
My $0.02

Re: assistance please 850 merc.

Could be lower plugs are dry because lower carb float is stuck shut (or misadjusted) and no fuel getting to cyls. Bad news if that is the case because those cyls are running dry, ie no lube.

Re: assistance please 850 merc.

stormmn said:

this engine does not have coils, it has a CDI switch box/coil and all plugs are getting fire as I tested the output with a spark tester before putting into service...

Click to expand...

My apologies,I should have checked that year first.

If indeed you have spark and cleaned out your carbs, then I am guessing the maybe you have crossed the plug wires up?

I am still a little confused when you say plugs are dry vs wet.

Plugs should not be wet.
They may have a little burnt oily residue but there should not be raw gas on them.

They should also be hot right after running and the electrode insulator should be a nice tan color with a dark streak on one side from the burnt oil.

These are surface gap plugs you are running correct?

The dry plugs, are they bone dry with no sign of burnt oil, clean and cold with pure white electrode insulators?

Re: assistance please 850 merc.

A dirty dry is good wet is bad, I would suspect no spark on top plugs, Try to test in the water/lake under a load if you can, leave on trailor ....that is if it isn't froze over.

Re: assistance please 850 merc.

Like Moody blue posted, bottom carb getting no fuel or vermin/dirt dauber nest has reeds blocked on lower

Re: assistance please 850 merc.

Storm, You might run it at idle and pull some plug wires to see if all 4 are firing. I could not tell if the carbs were rebuild recently or two years ago. If two years ago, they could be dirty again. If they were rebuild recently, it is likely the idle mixture is set incorrectly. Richen them 1/8 turn and try again.

Stalling immediately upon advancing the throttle, is a classic symptom of too lean idle mixture.

Re: assistance please 850 merc.

so many questions, so few answers>>>unless you ask a girl, them sit back!

#1 Plugs are the correct NGK for the application..

#2 Carbs were rebuilt two years ago and again last week after the firt run and the engine still crapped out at high RPM.

#3 Sorry, no ice, I live East of Vegas, 64 deg. and sun on Lake Mead tues..

#4 I'm looking a Reeds as posibly being the problem, I have never delt with reeds before and do not remember seeing anything on servicing them in the Seloc repair book. will look further.

#5 Plugs>>top two are "wet" as in a small drop of oil fuel which is normal for a 2 stroke>>this aint my first 2 stroke Merc. the bottom two are dry as a bone which makes me beleive reed valve problem since the carbs were just gone through.

thanks and will keep all posted

Re: assistance please 850 merc.

Reed valves almost never fail. I recommend you test for spark on all cylinders and firing on all cylinders, and then work on idle mixture setting.

Re: assistance please 850 merc.

Check the filter screen if you have the flat top carbs, remove the tops, lift them up and see if you can pump fuel out of the seats. You can also do a quick check to see if fuel is in carbs by removing the hi speed jet covers and pumping primer bulb.