Grumman-581 wrote:

I have a 1998 Sugar Sand Mirage with a 175 hp Mercury SportJet engine in it
(basically an outboard power head mounted to a jet)... I've been having a
problem with it that seems to make me think that oil is being injected into
the cylinders after the engine has been shut down... When I try to start the
engine, it won't fire unless I spray a lot of starting fluid (ether) into
the air intake... Doing this will eventually result in the engine starting,
but it takes a couple of tries... Once it does start, it smokes a lot
initially, but after awhile, it runs normally... I have verified that I have
good fuel (drained the tank and examined it in clear bottles)... I have
pulled the plugs before using the starting fluid and they have quite a bit
more 2-cycle oil on them than I would expect was normal... They come out of
the engine looking like they had been dipped in 2-cycle oil... This would
explain the smoking after it finally starts using the starting fluid...
After it has run for awhile, I can restart it immediately after a shutdown
and there is not a problem... If I wait an hour, I had better have a can of
starting fluid with me... To say the least, this does not give me much
confidence in my engine and thus I'm extremely hesitant to shutdown the
engine until I get back on my trailer at the end of the day...

The Merc oil system is intended to fail "safe" (unlike the OMC system) so
as you can see the engine tank gravity feeds the oil pump & a crank rotated
disc controls metering with revs. Most (not all) failure modes mean gravity
will continue to give the engine oil so long as there is oil in the tank.

Your choices would seem to be;

(i) Take it to a dealer & have it "fixed" no matter the cost, but beware it
"might" be expensive, equally it might be a simple hose valve etc. Best ask for
a firm quote before allowing them to proceed.

(ii) Disconnect the oil system & just put tcw3 in the fuel tank. I accept
you're reluctant to do this however your concerns about "stale" fuel while
correct about the fuel, don't really impact on the oil. The oil held in the
current injection tanks also absorb moisture over the winter etc & this
moisture is the cause of many oil injection system failures, whereas if the oil
is in the fuel tank it's always properly mixed (every time the boat moves on
water or trailer) & will totally eliminate any concerns about oil starvation.

Some in this NG run very oil rich mixes & swear by them for long engine
life, equally 50 to 1 is plenty for normal use over the season & doesn't risk
carbon buildup behind the rings, a little more if the boat is not used for
months on end & if not used all winter then spray fogging oil in the air
intakes until it stops because of it.

K



Has anyone encountered this sort of problem before?

Mercury says in the engine manual not to pre-mix the oil and gas, but rather
to use the oil injection tank... Since it has an inboard tank and a fuel mix
is likely to stay in there for a period of time and I've always heard that
you should not use a 'stale' fuel mix for 2-cycle engines, I'm somewhat
hesitant to go the pre-mix route...

Suggestions?