93 40hp Mercury

[Uncle Krusty]

Well, it's the middle of the night and I'm supposed to buy a boat in the morning. It's a 93 sylvan pro yukon 15' with a 40 hp merc 2 stroke, also 93. I'm ok with the boat but would like to hear if anyone has experience with this motor. It starts up ok and runs on muffs, but that's about all I know. I'm going to check the compression before I close the deal. I'll post pics if I go through with it!

 

[JL8Jeff]

Is that a 2, 3 or 4 cyl motor? I have a 94 60/45 jet and the oil injection was bad when I got the motor so I removed it and run pre-mix. I had a couple of voltage regulator/rectifiers go bad a couple of years ago before I lost spark altogether. It turned out to be a bad stator. I replaced all the ignition parts with CDI brand parts and it's been running good since then. I rebuilt all 3 carbs as well after I pumped the ball too hard and blew out the mesh in the fuel filter allowing bits to get in the carbs, but that was my fault. They're not hard to work on but some of the ignition parts can get expensive if you want to stay with Mercury/Quicksilver.

 

[Uncle Krusty]

The compression was 110-115 on all four cylinders. It has two carbs. I'll run it in the can soon, maybe today. I'll also do the oh-boy-I-got-a-new-boat post later today. I've had several 2 strokes and they ALL had carb issues; would run ok in the can but crapped out on the lake, so my expectations are low.
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[thill]

Two carbs? Isn't that a 4-cylinder?

Either way, those tend to be very good motors. Carbs often have to be cleaned when you buy them, but once you do, those are great motors. Just keep fresh fuel in them, and use an inline filter. The biggest enemy is letting them sit with fuel in them, especially Ethanol gas.

Definitely use your additives, like Startron ethanol treatment or Stabil, if you have ethanol free fuel. Ethanol free is worth the extra dollar, especially at the end of the season. Many of us use the E10 in the spring, then go E-free as winter approaches.

 

[Uncle Krusty]

Yup, 2 carbs. It seems to be the last of an older design, called Classic(?). They went to 3 bangers at about the same time this was built. The boat has a built in tank, which is about 1/2 full of pre-mixed fuel of unknown age or composition and I have to figure out how to drain it. Then I'll use only ethanol-free.

 

[airshot]

I own a 92 Merc 40 hp 4 cylinder 2 stroke, probably the same motor...mine runs excellent, idles so slow you can almost hear each cylinder fire. Your carbs probably need a rebuild then adjusted on the boat in the water, not in a barrel !! Sounds like old fuel issues. I use both stabil and sea foam, always add a little each time I fill the tank. Also pull the fuel hose and run the carbs dry at the end of each outing. Pull the fuel line and as soon as I hear any change in speed or a stumble I shut it off !! Probably one of the best running motors I have owned in my 60 yrs of boating....knock on wood !! Mine is easier on fuel than my older twin cylinder merc 40 and my jonnyrude 40 twin cylinder. What ever Merc did to this " classic" was good ....as mine is a keeper !!! Once you get it runnun right, take care of it....many dont, then want to blame the motor and mfgr for poor quality...

 

[airshot]

Yup, 2 carbs. It seems to be the last of an older design, called Classic(?). They went to 3 bangers at about the same time this was built. The boat has a built in tank, which is about 1/2 full of pre-mixed fuel of unknown age or composition and I have to figure out how to drain it. Then I'll use only ethanol-free.

Is your oil injected?? Built in tank should be an oil tank only for the oil injection system. I have used ethenol fuel since it came out with not one issue, but I also use stabil or sea foam on each fillup. Also used ethenol gas in my 1983 I/O after changing the fuel hoses and filters and no issues in the 8 years I had it. Do the proper maintenence and ethenol eill not ve a problem!!

 

[Uncle Krusty]

According to this chart they made these small 4 cylinders from 1989 through at least 1996. I can't find a manual, any ideals?

 

[Uncle Krusty]

Is your oil injected?? Built in tank should be an oil tank only for the oil injection system. I have used ethenol fuel since it came out with not one issue, but I also use stabil or sea foam on each fillup. Also used ethenol gas in my 1983 I/O after changing the fuel hoses and filters and no issues in the 8 years I had it. Do the proper maintenence and ethenol eill not ve a problem!!

The oil injection system has been abandoned, as seems to be common. The tank I'm talking about is in the boat, under the floor, 17 gallons, I think, and is about half full of pre-mix.

 

[cyclops2]

First rule of buying ANY NEW or USED boat / engine ?
ASSUME there are incorrect parts through the motor AND gas tank.

Like wrong spark plug. pull & look at the plugs for anything odd like color or oil. Ratty spark plug wires not fully inserted on things. Fuel filter change or install one. DO NOT USE that gas in the tank. DUMP it on weeds. Mix up the correct ratio. USING ONLY water-cooled 2 stroke oil !!
Basic throttle linkage check. shine a flashlight into carburetor move throttle linkage all the way open. Adjust if needed correctly. Borrow a timing light and check timing cam & linkage. That is all without taking apart a good carb & guessing about it. Enjoy the winter.

 

[airshot]

First rule of buying ANY NEW or USED boat / engine ?
ASSUME there are incorrect parts through the motor AND gas tank.

Like wrong spark plug. pull & look at the plugs for anything odd like color or oil. Ratty spark plug wires not fully inserted on things. Fuel filter change or install one. DO NOT USE that gas in the tank. DUMP it on weeds. Mix up the correct ratio. USING ONLY water-cooled 2 stroke oil !!
Basic throttle linkage check. shine a flashlight into carburetor move throttle linkage all the way open. Adjust if needed correctly. Borrow a timing light and check timing cam & linkage. That is all without taking apart a good carb & guessing about it. Enjoy the winter.

Yes, I agree there...no sense wasting labor and money if you dont need to. I would mix a strong ratio of sea foam for the first few gallons of premix, might help flush any gunk out and save a carb rebuild !! And yea, unless you trust the prior owner, dump the old fuel !!

 

[thill]

Agree with all the fuel comments above.

Rather than dump the fuel, let it settle, so any water will go to the bottom and siphon that off. Then add a couple of gallons at a time to your truck's half-full tank. You won't notice it. No smell or anything. Just free gas recycled and saving you money.

I've done this with EVERY tank I drain for many years. The guys at the marina fought over who got the old gas. I thought they were crazy, but they laughed. Then I tried it, and sure enough, no issues. Just don't fill up your tank with it.

 

[airshot]

Agree with all the fuel comments above.

Rather than dump the fuel, let it settle, so any water will go to the bottom and siphon that off. Then add a couple of gallons at a time to your truck's half-full tank. You won't notice it. No smell or anything. Just free gas recycled and saving you money.

I've done this with EVERY tank I drain for many years. The guys at the marina fought over who got the old gas. I thought they were crazy, but they laughed. Then I tried it, and sure enough, no issues. Just don't fill up your tank with it.

I would agree, but I believe the poster thinks the fuel in the tank is of an unknown age.. Season to season would not be an issue, but if the fuel were "years" old, I would not take the chance. My last tank of fuel for the season, gets a good dose of stabil or sea foam and left fairly full, the next season It runs great...however, if the fuel has sat for multiple years, I would only use it as weed killer!!

 

[airshot]

According to this chart they made these small 4 cylinders from 1989 through at least 1996. I can't find a manual, any ideals?

Found mine on ebay, used but in good condition. I used the model and serial number to find the correct one. 15 bucks, well worth the expense !!

 

[Uncle Krusty]

Yes, I agree there...no sense wasting labor and money if you dont need to. I would mix a strong ratio of sea foam for the first few gallons of premix, might help flush any gunk out and save a carb rebuild !! And yea, unless you trust the prior owner, dump the old fuel !!

For sure. Old fuel is always suspect. It's a built in tank, 17 gallons, I think. Looks like it will have to be pumped or siphoned out. Fun. I wonder what's lurking at the bottom of that thing. In the meantime I'll hook it up to a portable tank of fresh go-juice. But not today, gotta work!

@cyclops2 Great suggestions. The plugs are new. The seller had the motor serviced, but I'm not sure what was done.

Agree with all the fuel comments above.

Rather than dump the fuel, let it settle, so any water will go to the bottom and siphon that off. Then add a couple of gallons at a time to your truck's half-full tank. You won't notice it. No smell or anything. Just free gas recycled and saving you money.

I've done this with EVERY tank I drain for many years. The guys at the marina fought over who got the old gas. I thought they were crazy, but they laughed. Then I tried it, and sure enough, no issues. Just don't fill up your tank with it.

The fuel is pre-mixed with oil. My Jeep's not going to like that much. I guess if I siphon from the bottom I could pick up some water. I'll try to drain the whole thing. Won't have to buy fuel for the chain saw and Mantis tiller for a while.

 

[thill]

I strongly recommend using it in a vehicle rather than a small, 2-stroke engine.

If you MUST use it in a small engine, add some Octane Boost to it and dilute it into a large tank of fresh fuel and it will be fine. Just don't let it sit around. Use it immediately.

Use it in your truck. A couple of gallons of even the oldest gas in a mostly full tank will do absolutely nothing that you can notice. I put a max of 5 gallons in my 27 gallon tank. As I say, I've been doing this for many years. The tiny bit of oil in 3 gallons of gas means absolutely nothing when mixed in 15 gallons of gas. No smell, nothing.

Just don't fill your tank up with that stuff. Yeah, I tried that once in the past. The engine started pinging noticeably. Had me worried. I put in a bottle of octane boost and topped off the tank and it was fine. I'll never do that again, but the small amounts don't affect it in any way.

 

[Uncle Krusty]

I strongly recommend using it in a vehicle rather than a small, 2-stroke engine.

If you MUST use it in a small engine, add some Octane Boost to it and dilute it into a large tank of fresh fuel and it will be fine. Just don't let it sit around. Use it immediately.

Use it in your truck. A couple of gallons of even the oldest gas in a mostly full tank will do absolutely nothing that you can notice. I put a max of 5 gallons in my 27 gallon tank. As I say, I've been doing this for many years. The tiny bit of oil in 3 gallons of gas means absolutely nothing when mixed in 15 gallons of gas. No smell, nothing.

Just don't fill your tank up with that stuff. Yeah, I tried that once in the past. The engine started pinging noticeably. Had me worried. I put in a bottle of octane boost and topped off the tank and it was fine. I'll never do that again, but the small amounts don't affect it in any way.

You are saying to use 2 cycle mix in my old Jeep? I take your point regarding dilution, but I can't bring myself to do it. And it's moot anyway; the seller tells me he emptied the tank and put in fresh fuel a few weeks ago. So I can add a Stabil-ized gallon or so of fresh gas to the tank and I'm good to go. And some Seafoam for good measure. I should have time to run it in the tank later this week.

Now to locate a manual.

 

[Tinny Fleet]

All the above advice is good, however I might add one more test before reusing the old fuel/oil mix - the sniff test. If it smells like turpentine I'd dispose of it, not reuse it.

 

[thill]

That's good to hear. Not an issue now.

For what it's worth, the tiny bit of oil in the 2-stroke mix will help lubricate your fuel pump and fuel injectors. That's why Marvel Mystery oil helps smooth things out in a lot of engines.

But I get it. I've put hundreds of gallons through my old 2005 F150 work truck, and that truck has given me zero problems since new. (Great truck!) Even so, I'm not inclined to run it through my new truck with a 3.5L Ecoboost twin turbo engine. You got me there, ha ha!

 

[Uncle Krusty]

I hope to run it in the tank this weekend. Also shopping for a kicker. For me, having been left in the lurch by the main motor, the kicker is more of a plan B than a way to go slow and drag gear around. I'm not putting that boat in the water without it.