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Would Quicksilver Premium Plus result in oilier output/residue than Quicksilver Premium

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vadinghy

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I inadvertently picked up a container of Quicksilver Premium Plus from Walmart recently (its a bit of a trip to get it), and didn't realize what I'd gotten until I returned home. I'd previously been running the Quicksilver Premium. I ran the old oil (Quicksiver Premium) down to near the bottom of the reservoir, then filled up with the Premium Plus. Engine is running fine (though I do think its bogging a tiny bit more on holeshot), but I've noticed that the exhaust ring, spindle and nut of the prop are much oilier than they were previously. Previously, they had a light, dry, carbon'ish coating on them, but were largely dry. Now, they are definitely coated in an oily film - not dripping off or such, but enough to leave a sticky black mark on your hand if you touch anywhere in there. I presume that this is due to the difference in the oils used in the Premium vs Premium Plus, but want to be sure that I'm not causing problems (fouling, clogging, etc) for the engine, and I do worry a little bit that I may be leaving more oil behind in the water, when running the engine. (I'm a boat noob, BTW, so please keep that in mind with this thread :)

So, does this sound normal? Is it anything I should be concerned about? Should I stay with the Premium Plus (now? going forward?) or revert back to the Premium?

BTW, this is on a 2001 Mercury 90 HP 2 stroke (oil injection), which runs very well and has a consistent 115 psi compression reading on all 3 cylinders, FWIW.

Thanks for any assistance!
 
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Engine is running fine (though I do think its bogging a tiny bit more on holeshot),
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What do the spark plugs look like? All 3 firing? Premium Plus won't hurt anything. Just use it up and refill w/Premium. I run my 115 HP on Cabela's synthetic blend for $17/gal....no problem w/it. Many others use Wal-Mart branded TCW-3 2 cycle oil w/out any problems.
 
If the motor is up to operating temp it should burn off whatever oil you are using.

Aside from the plugs, when was the thermostat last serviced (or is it even present) - a properly functioning thermostat will smooth out the idle and keep the powerhead at a temp where it will burn up the oil. NO thermostat will always leave the motor running cold (unless you boat in a hot tub), which will leave excess/unburned oil coming from the exhaust...
 
Good question on the thermostat - I have no idea if its good, or even present. I've just recently purchased this boat, and while I had a marine mechanic check it out, he didn't specifically check the thermostat. Is there a way to check it, short of pulling it out? Can I take a temperature reading of the engine block after its been running 1/2 hr or so, and get a sanity check on its temperature range? (I've got an IR thermometer that is reasonably accurate.)

I replaced the plugs when I purchased the boat. (There were Autolites in it at the time, and the mechanic made me promise the first thing I'd do was go buy 3 NGK's, which I dutifully did. :) The plugs were clean and in good working order (the Autolites) when checked by the mechanic. I haven't pulled the NGK's to look since the oily residue showed up in the exhaust, but they've got *maybe* 12 hrs on them since they were put in, of which 2-3 hrs would be w/ the new oil. (The mechanic did check the spark, using a spark tester board, and they were all going strong, as well.)

The other variable is that I have recently gone from a 3-blade 21" pitch prop to a 4-blade 19" pitch prop - at the same time that I inadvertently switched oil - can't imagine that being a related issue, but in the interest of making all the variables known, that's the other change that occurred between the old 'dry' prop ring/innards and the new 'oily' prop ring/innards. (When I changed the prop, the prop nut was clean and gold'ish-colored. Its black now, after only 2-3 hrs of run time.)

I've got about 1/4 of a jug of the Quicksilver Premium left - I could siphon the Premium Plus out of the oil reservoir and run w/ the straight Premium again, I suppose, to see if things stay clean.

The oily residue really only seemed to start when I switched oil, so while a mechanical issue is obviously not impossible, I'm reluctant to pin it too readily on a motor problem, especially since the motor is running as well w/ the new oil as it was with the old oil (able to pull a slalom skier out of the water, pulls the kids on the tube well, hops up on a plane quickly, WOT was about 43 mph w/ the 3-blade and is about 41 mph w/ the 4-blade). It does seem to bog down momentarily when making the hole shot from a dead standstill every now and then (primarily the first one or two after leaving the dock), but that could also be attributable to the 4-blade prop, I suppose. (ie, as opposed to the oil, which sounds improbable) Skiers are coming up out of the water *much* more quickly w/ the 4-blade, so all in all, I'd say the engine is running strongly.

I appreciate the info and input. Please let me know if there is a way to test the thermostat, or to at least take a sanity check on the operating temperature range. I may clean up the prop innards, suck out the Premium Plus oil, put the remaining Premium in, and see how things look after some running around the lake for an hour or two.

Thanks for the help!!
 
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To test the thermostat you need to pull it.

You could use the IR thermometer to get a rough idea of engine temp (should be in the 140-165 range on average - over heat occurs at 190/ below 140 is "running cold"). Take the temp from the side of the block (you can see the (bulge) of the cylinders). This motor is a "headless, split block" also called a jughead, so where you would expect there to be a cylinder head it's really just a "water jacket cover" and the temp at that point will always be lower than block itself.

This model has both a thermostat and a poppet valve to control temp - they are located right next to each other (thermostat under the cover on the left up near the top sparkplug).

The thermostat should handle everything at lower rpms (under 2500'ish rpms), so you can idle/no wake for a bit and check the temp. As the rpms increase the water pressure from the water pump also increases and the poppet should begin to open (just a spring and a diaphragm) to allow the added water volume by. It's not that the thermostat "stops" working, it's just that most of the water bypasses it and exits through the poppet channel.

If the poppet is not "closing" at lower water pressure, that could also result in "cold running", mimicking a faulty (stuck open) thermostat, giving the same symptoms - crappy idle, oil fouled plugs etc.

A thermostat goes for about 25 bucks and poppet/diaphragm/spring/grommet is under 15 bucks. Both are worth changing since you don't know the history, but definitely get the infra red on it, you may be able to leave the thermostat/poppet service until next season.

Just one other note - the autolites were fine (predated the NGK's in the Thunderbolt 4 ignitions) - just never, ever Champions unless you are really in a bind. The autolites and NGK's (resistance) is suited to the high power Merc/Yamaha ignition systems - Champions are for OMC/Suzuki...
 
Graham I looked at the parts for the year range and it shows a 120F. T'stat being used...did I look in the wrong area?
 
You guys are awesome - Thanks! This is my first post, and its already turning into a great education. :) (Granted, I'm starting from about zero, but still... ;-)

I'll check the temp as instructed on the next trip out, and will pull the plugs and take a quick peek at them prior to that. (If the exhaust outlet is oily, I can only imagine the plugs would be, too?)

I was intrigued by the NGK plugs - they didn't have a normal-looking gap setup - looked a bit more like a glow plug from an RC engine (little coil up inside the plug body), but clearly, they've got a spark wire going to them, so they're sparking somewhere. The Autolites were a more traditional-looking setup. The engine ran fine w/ both - couldn't really tell a difference by sound, feel, etc.

Sounds like replacing the thermostat and poppet is a good ideal regardless - I'm guessing I ought to go ahead replace the impeller, too, while the tools are out. Just trying to minimize the 'financial attentions' of the family accountant this month, given the significant outlay for the boat and various accessories within the past month. :) $40 is a small price to pay though, if it needs it. (Better that, than some much larger sum soon thereafter for want of a $40 pm task, eh?!?)

This is our first boat, and we're loving the little thing - I'm hoping it'll last us a fair number of years, and I'm counting on it being the 'hook' to keep the kids wanting to continue to interact with me as they get into their teen years, so I need to take good care of it now. :eek:)
 
No, it could well be a 120 degree stat - that's just the point that it opens fully which would still allow the motor to reach 140'ish degrees (which is "typical' for Merc but not written in stone).

Regardless of the thermostat, the guarding system (or temp alarm on the simpler version) will not "pop off" until 190 degrees, and anything under 170 is considered "ok" (circuit alarms at 190, and shuts back off at 170).

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Your NGK plugs sound like "surface gaps", so no little thingy to gap with a gauge. The spark jumps to the edge of the sparkplug instead of that from the center electrode to the ground electrode (that "thingy" you gap).

Surface gap plugs are the superior choice for "sustained" higher speed running (above 3500 rpms). If you use the motor for trolling or run alot at "no wake" speeds, it's best to select a "gapped" plug if one is specified for your particular model...

Try them out "the way you run the boat" and if you are dis-satisfied with the performance, switch back to a gapped plug if available...
 
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