Hello , I have a problem with a OMC, (does the Omc stand for ol misery
and confusion ?) the motor starts great with little or no priming of
the fuel bulb but after a while aprox 10 min in cool weather or 5 in 90
deg weather the engine drops to about 1/2 throttle and has a dead miss
any where above that, replaced all fuel lines and bulb from fuel pump
back to the tanks, same problem. If you stop for about 30 min. with it
turned off, it will throttle up to full rpm with no miss for the same
time frame then start missing all over .I have also replaced the plugs
and wires with no improvement.What next ? I'm ready to back off and
punt, striper season is upon us and the boat won't keep running long
enough to fish !!
Thanks for reading and any input would be great,
Mark (WV)

Mark(WV) wrote:
Hello , I have a problem with a OMC, (does the Omc stand for ol misery
and confusion ?) the motor starts great with little or no priming of
the fuel bulb but after a while aprox 10 min in cool weather or 5 in 90
deg weather the engine drops to about 1/2 throttle and has a dead miss
any where above that, replaced all fuel lines and bulb from fuel pump
back to the tanks, same problem. If you stop for about 30 min. with it
turned off, it will throttle up to full rpm with no miss for the same
time frame then start missing all over .I have also replaced the plugs
and wires with no improvement.What next ? I'm ready to back off and
punt, striper season is upon us and the boat won't keep running long
enough to fish !!
Thanks for reading and any input would be great,
Mark (WV)


OMC + Outofbusiness Marine Company.

What sort of OMC motor do you have? What year?

"Mark(WV)" wrote in
oups.com:

eplaced all fuel lines and bulb from fuel pump
back to the tanks, same problem

Step 1 - Boat in water - Engine DOWN. Point the bulb so the inlet (tank
line) is down and the outlet (engine hose) is up. Pump the bulb. Does it
get impossible to pump quite quickly, indicating to me that the float
valves have all closed and no more gas can be pumped into the engine,
like it should, or can you just keep pumping gas in it until you can see
it run out into the water? If the bulb won't pump up hard and refuse to
pump any more, even leaking just a little, something bad is leaking. If
you can't SEE it leaking gas anywhere as you continue to squeeze hard on
the bulb, the stupid rubber diaphram in the cheapassed pulse fuel pump
has a hole or is cracked.....which FLOODS the cylinder crankcase the
pulse line is sucking on...probably the cylinder that's skipping because
it's FLOODED. Take the fuel pump apart and replace the diaphram...then
TRY THIS TEST AGAIN! The NORMAL version of this test is for the bulb to
pump easy until the carbs fill, float in bowl shuts off gas flow, bulb
cannot be pumped another drop until the motor starts.

Ok, let's now assume the bulb test was "NORMAL", the bulb is all pumped
up....now what?

2 - Take the boat out with two people in it...him driving (sexist?) and
you back by the engine. Run it until it runs like crap and starts to
skip as you say. Pump the bulb just like above, again. Does the engine
perk up and come right back up to speed? IF it does, the fuel pump isn't
pumping. Could be a clogged pulse line from the pump to the crankcase.
Could be the 18-year-old diaphram in the fuel pump is so hard it can't
flex enough any more to keep the carbs full against the float stops.
"NORMAL" for this test would be you can't pump the bulb any more than a
half-a-squeeze because the normal fuel pump has already filled the carb
floats, isn't leaking fuel into the pulse line, so there's no place for
the bulb to pump more gas into. If you pump the bulb and the engine
stalls, one of two things is wrong....hole in the diaphram you should
have already found and fixed in test 1 above...or...the float valve in
one or more carbs is sticking closed and the float bowl is emptying
itself because the float valve is clogged or won't open enough to keep up
with the fuel flow into its gullet....

Disassemble and clean the carbs, anyways, in an engine this old. It's
all full of crap that clogs the jets, fuel residue from all the times it
was stored with gas in the float bowls (shellac) etc.

Does it have a NEW fuel filter....or any filter at all? There should be
a screen on the fuel pump, all clogged up with crap that fell into the
tank for 18 years...(c;

That primer bulb on a static or running engine is one of the finest
troubleshooting tools on the boat. See why?

I stumbled upon a stalled boat in the river...engine cover off...stunned
silence staring in there wondering what-the-hell?... I always stop.
We're supposed to help each other, ya know. He wanted a tow. "Put the
engine back down and pump the bulb for me.", I asked, politely, trying
not to sound too smug in his hour of misery. He squeezed, the bulb
pumped easy! He let go, the bulb stayed squeezed and wouldn't refill....

"Is your gas tank valve off?", I asked? Nope...it was on. Hmm...."Is
anything sitting on the hose?" "Ah just the cooler.", he replied. "Take
the cooler off the hose and watch that collapsed bulb.", I suggested. Of
course, as soon as he got the BEER off the HOSE, the bulb popped back
out. "Pump the bulb until it gets hard.", I continued. He did. It did.
"Will it start?" No, he'd killed the battery cranking and cursing and
cranking and cursing. It would hardly click. "Got a hand start rope?",
I asked. No, he never heard of any such thing. I got out mine and
handed it over to him. "Turn on the switch, open the throttle and push
in to get the choke to close. It clicked, there was some battery left.
I wrapped it once, pulled and the old girl sprang to life, to his
amazement. Evidently, the beer had shifted to the end that was sitting
on the hose!

Two stroke motors AREN'T rocket science if you sit back and look at
them....spark - check.....gas - check....it'll run unless it won't turn
over because it siezed...

Another time I fixed a stranded boat by plugging the MAN OVERBOARD KEY
back into the console!....(c; Even the owner found this hilarious. His
wife sure didn't!...oops! I don't think he was gonna get HIS bulb
squeezed for a while.

Mark(WV) wrote:
Hello , I have a problem with a OMC, (does the Omc stand for ol misery
and confusion ?) the motor starts great with little or no priming of
the fuel bulb but after a while aprox 10 min in cool weather or 5 in 90
deg weather the engine drops to about 1/2 throttle and has a dead miss
any where above that, replaced all fuel lines and bulb from fuel pump
back to the tanks, same problem. If you stop for about 30 min. with it
turned off, it will throttle up to full rpm with no miss for the same
time frame then start missing all over .I have also replaced the plugs
and wires with no improvement.What next ? I'm ready to back off and
punt, striper season is upon us and the boat won't keep running long
enough to fish !!
Thanks for reading and any input would be great,
Mark (WV)



Are you losing a spark to one cylinder? Does this motor use twin
magnetos or does it have a distributor? I've never worked on an outboard
this new so I'm not intimately familiar with them.