[alphaboat]

I have about 600 hours on my Merc 50 2-stroke.
Always been a great engine and never any problems until about the first week in October.
The Voltage regulator went bad on it at that time and after taking a look at the whole situation have concluded that was due to water in the cowling not draining out efficiently due to a clogged drain. Once in a while I find a "skinny spot" in the Columbia River and suck up some sand, which plugs up the spitter. When I remove the hose under the cowling to clear the spitter, a portion of the sand in the hose ended up down into the cowling and found it's way to the drain. The drain has a check valve in it (well, I know that now after ruining the first one trying to pass a wire through it to "clean" it!!) and the sand won't pass through that so it quit draining. Anyway, the result was a slow draining cowling with higher than normal residual H2O under the hood. The regulator sits at the bottom of the "black box" and, even though it is potted, I believe moisture got in there and shorted it out. No big problem. A trip the trusty Mercury dealer (I know ....I could have gotten a cheap after market unit on the web...but I like OEM parts) and $197 later I was back in business.
However, during the first few weekends in November (I had the boat out fishing salmon 2-3 days every week from August through November) the engine started smoking more that usual and not running as smoothly at low rpm as it has always in the past.
I dismissed it as "we'll, it is getting colder and maybe it is just extra steam".
I am colorblind so I was trying to convince myself the "cloud" wasn't as blue as my buddies were telling me it was.
I decided to try decarbing with Seafoam but still had lots of blue smoke on the next few outings.
Then, on the last trip out (good timing eh?) the engine started running very roughly and started "stuttering" at higher rpm.... something I have never experienced with this engine in the past.

Salmon season was done anyway so I took the boat to the mercury dealer and they looked the engine over and are saying they believe the oil injection pump is the culprit. They claim it is sending too much oil to the cylinders and in turn fouling the plugs causing the high amount of smoke and poor engine performance.
I reluctantly told them to go ahead with the work and am waiting for them to let me know it is done.

Question: How does a worn out pump start pumping too much oil? Seems odd to me.
Anyone out there have history regarding trouble with oil injection system on Mercury 2 strokes?

Don B

[Laddies]

When the pump goes bad it results in not enough oil. To much the chances are very good that the rod number 27 has come unhooked or broken a end the rod runs between the pump and throttle linkage and adjusts the oil mix at differant RPMs. http://www.mercruiserparts.com/Show_...n+Co mponents

[alphaboat]

So......I guess I need to ask a few more questions.
Sounds like I am possibly being taken for a "$300 cruise" on this one.
If you were in my place, what questions would you ask or in what way would you respond to them telling you a bad Oil Pump is causing too much oil to get to the engine?
Thanks for the support.
Don

[j_martin]

I'd get a service manual and do it myself, or at least know what the mechanic is up to.

On the pump. They don't really wear, as it's a slow moving gear pump pumping incredibly high quality clean oil. The drive gear is plastic and can shear, which stops oil flow and sets off the alarm. There is a valve attached to the throttle linkage that varies the oil flow depending on throttle setting, less at idle, more at WOT. If the linkage fails, a reasonably engineered system would fail to full rich.

The book would have adjustments and tests in it.

John

[achris]

The very first thing I'd be doing when I went to get the boat would be to ask for the old pump back. Even though the dealer has put a new one in, you still own the old one. If he can't return the old pump, ask him why you should pay for a pump that he can't prove is new (by returning the old one to you). It didn't matter what we replaced in our shop, the owners got the old parts back, apart from engine and gear oil, they had to trust us on those.

My experience with these engines is that about the only thing that goes on them that could be causing your problems is that the plugs are worn. New set of plugs and it should be good to go for another couple of years. Fixed quite a few like this. Never charged anyone for a new oil injection pump either. Think about it, lots of smoke means fuel not being burnt properly, missing at high and low speeds means fuel not being burnt properly. What can cause the fuel to not be burnt properly? Worn spark plugs, and you did say it was getting worse. Nice new set of NKGs and you'll be happy boating again.

Chris................

[alphaboat]

To bring everyone up to date with the progress of this repair.
The Dealer has replaced the oil pump but has told me there is still a high RPM miss and is now going into the reed to check them out.
I will let you know how this ends up.

[rodbolt]

sounds like they are a pokin and a hopein.
not a good way to troubleshoot.
a simple oil consumption test can isolate a pump issue. most the problems we had were pump shaft seals leaking.
that motor doesnt use the platic gear or the rotational sensor.
the fuel pumps go bad with age.
plugs can be checked with a Kv tester to identify weak or failing ign components.
normal Kv on that motor will be around 10-15 Kv with surface gap style plugs and 7-10 with side electrode style plugs.
mostly we did not have many issues with the oiling system on that motor.