What to do first? Sat for 5 years. Old Mercury 4hp Outboard motor

[Carl Wonderful]

Hello,

New to Outboards and don't want to do something dumb. This motor was said to still run good. But hasn't been run for 5 years. What are the first steps and what not to do? 1973 (ish) Mercury 4hp outboard. Came with my 1971 Catalina 22.

I know I need to get good gas...
1. But do I have to drain any old gas inside?
2. Think mix is supposed to be 50:1.... what kind oil do I buy?
3. What kind of gas? Ethanol free? premium or anything from the gas station?

I have a barrel I can fill with water to run it in.

4. Any risk to damage it...should I test to see if its not "seized"..
5. I see lot people taking spark plug off and spraying some kind oil into it. Necessary? If so what kind oil?
6. Should I loosen the bottom "gear" oil nut to see if the oil is black/creamy/clear/ or even empty?
7. its definitely a 2 cylinder, right?

Any other info greatly appreciated. I basically know nothing so clear and specific steps and products would be great!!!

 

[shemandr]

Yes new gas.
No, don't save the old.
2 cycle oil is OK. I wouldn't spend on premium brands until it runs.
Ethanol free if it's available.
You can tell pretty fast if it's seized.
Marvel Mystery Oil is a good choice to squirt into the cylinders prior to starting. Pull the start cord to distribute.
Replace the lower unit lubricant if the motor coughs twice while trying to start.
Yes, 2 cylinder.
You'll prolly need to rebuild the carb before it will run. For sure disassemble and clean. Once you do that you might as well do the rebuild.
Add a fuel filter and make sure all fuel connections are tight.
Maybe it will run.

 

[dlochner]

In addition to @shemandr's suggestions:

Change the water pump impeller. It has likely taken a set and will not pump a sufficient volume of water to cool the engine.

Put a new properly gapped spark plug in it.

Definitely use ethanol free gas if available, if it's not, drain the carb after running the engine and drain the internal fuel tank.

 

[Rich Stidger]

Ordinary gas with 10% ethanol is ok for now, but after you get it running switch to ethanol free if you want trouble-free running. Ethanol will trash the carbs on these small engines in less than a boating season.

 

[marcham]

Honestly, I'd just buy a new carb.

If you don't want to buy a new carb, take it apart and clean it before you do anything else.Might want to consider replacing the fuel hoses, as they may be clogged....

Sometimes you get them started, then a little piece of crap goes and blocks the jets, then it runs worst....

 

[Project_Mayhem]

You might have some luck by draining the bowl, filling it with carb cleaner and giving it a few pulls to flush the carb out. I had a mechanica do that to get my 140hp two stroke running again. Next step after that would be a carb rebuild. Take it step by step so you don't dump too much money into something that's not going to run right

 

[Indysailor]

2 cycle engines are remarkably capable of sitting for a long time and firing right up. I'd leave it in neutral, drain the carb bowl, use new fuel, new plug, see if it fires up. Have a can of ether on hand to cough it to life. If it doesn't start, soak the carb, clean the jets, repeat. Or as suggested, just buy a new carb.

 

[Rich Stidger]

For engines under 10hp, carb disassembly and soaking in carb cleaner works well. If you have access to an ultrasonic cleaner, put the carb parts and cleaner in it and process. For 4-cycle engines, use of an ultrasonic cleaner is essentially required due to the much smaller passages in the carb vs a 2-cycle engine. Since you have a 2-cycle engine, you can probably get by with just an overnight soak.
But once clean and running, only use E0 gas.

 

[BigEasy]

Might be difficult to find a new carb of that vintage; however, a rebuild kit should be available. Agree with others; remove bowl & clean, empty tank & replace with fresh fuel / oil mixture, & fuel filter (if one is present). Check spark plug fire. If you have spark & it won’t start, time to disassemble carb & clean with carb & choke cleaner. Would be great if you have access to an ultrasonic cleaner. (check harbor freight). If it was stored with ethanol gas, the Carb is likely corroded beyond repair. If you get it running, as others have mentioned, install new water pump impeller, lower unit oil, fuel hoses , fuel filter, & a new spark plug. If no luck, perhaps an outboard mechanic can get it going. Surprisingly there are quite a few of these vintage outboards that are still running. I once had a 50 hp Mercury outboard that would start but not rev to normal rpm’s if it sat unused longer than 4-6 months. Carbs would get gummed up & this was before ethanol. Best of luck.

 

[rgranger]

Honestly, I'd just buy a new carb.

If you don't want to buy a new carb, take it apart and clean it before you do anything else.Might want to consider replacing the fuel hoses, as they may be clogged....

Sometimes you get them started, then a little piece of crap goes and blocks the jets, then it runs worst....

YEP!

That little piece of can come from the hose. Also make sure the gas can is clean and does not have any debis.

When I first started my boat journey, I made a critical error. I purchased a used OB and did not change out the lower unit oil. It was crap and within a few trips I trashed the gears. So I would just change out all of the fluids.

Open it up anything that will open, (plugs, lower unit etc.) and spray it all down with carb cleaner until it runs clear. Something like this from AutoZone

Replace the lower unit oil. You can buy gear oil in the fishing section of walmart.

Replace the carb...you can get a new Carb for $50 on Amazon

Amazon.com: TC-Motor Carburetor For 4HP 5HP Mercury Mariner Quicksilver Outboard 3303-812648T For Mercury Mariner Outboard Part # 812648 812648T : Automotive

Buy TC-Motor Carburetor For 4HP 5HP Mercury Mariner Quicksilver Outboard 3303-812648T For Mercury Mariner Outboard Part # 812648 812648T: Carburetors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Replace the impeller... here is a new impeller (Also Amazon)

Amazon.com

Replace the fuel hose....You can get fule hose at any autoparts store. Grab some of that while you are getting the carb cleaner... might as well pick up a fuel filter while at AutoZone.

On the topic of ethanol gas... if you run the carb dry after EVERY use... you might get lucky and your carb will last more than one season using e10% ethanol gas. Ethanol absorbs water from the air... and when the gas dries, it leaves behind water in the carb's bowl. This makes rust... the rust tunrs into that will foul your injectors... and pits the carb.

So if you can get ethanol free gas, use that... and I still run my carb dry after every use even with the "good" gas.

When you come into port... just tie off to the dock and then disconnect the fuel line... let the engine run while you make the boat ready to put on the trailer, off load your cooler etc. Eventually the engine will starve and now your internal engine parsts are dry.

 

[dlochner]

About fuel hoses. Modern USCG approved fuel hose has a liner inside the hose to help reduce permeation. The glue holding the liner in place can fail when this happens the liner collapses under suction and cuts off the fuel supply. It was an expensive lesson.

 

[rgranger]

It was an expensive lesson.

Was that an inboard diesel? I'm struggling to understand the difference between a 3.5hp Tecumseh lawnmower engine and a 4 hp OB and why I would need a special fuel hose just because the motor is on an OB instead of a lawnmower. But I am always happy to be educated...

 

[dlochner]

Was that an inboard diesel? I'm struggling to understand the difference between a 3.5hp Tecumseh lawnmower engine and a 4 hp OB and why I would need a special fuel hose just because the motor is on an OB instead of a lawnmower. But I am always happy to be educated...

It was the hose for the external tank on the dinghy motor. The expense was shop time for the mechanic to tell me nothing was wrong with the engine and shop time and hose for the new fuel line.

There are 4 different USCG ratings for fuel hose. Types A1 and A2 are designed to have fuel in them at all time and are flame resistant. Types B1 and B2 are not designed to have fuel in them at all times and are not tested for flame resistance. These ratings are especially important for fuel hoses in enclosed spaces. A1 and B1 are more permeation resistant.

https://defender.com/assets/pdf/trident/uscg-fuel-hose-ratings.pdf

 

[Timm R Oday25]

Do not spray any either based propellant into a two stroke engine ! I did that on a brand-new very expensive Stihl chainsaw and paid the price . The ether washed the oil away from the cylinder wall and the piston rings got scored . Very pricey lesson .
They do make a starting spray fluid especially for two strokes . It must say so on the can

 

[BigEasy]

I concur that ether can be damaging to engines, have read that an aerosol spray, such as WD40 is safer.

 

[BigEasy]

I'm struggling to understand the difference between a 3.5hp Tecumseh lawnmower engine and a 4 hp OB and why I would need a special fuel hose just because the motor is on an OB instead of a lawnmower. But I am always happy to be educated...

Some rubber fuel lines are susceptible to break down with use of ethanol. Better grade fuel lines resist degradation of rubber in the presence of ethanol. Regardless of what type of fuel line you use, I would avoid ethanol if possible. I do not use ethanol fuel in my outboards nor home power equipment. At one time, I purchased a run about whose previous owner used ethanol, the rubber gas lines were literally petrified.

 

[Indysailor]

Do not spray any either based propellant into a two stroke engine ! I did that on a brand-new very expensive Stihl chainsaw and paid the price . The ether washed the oil away from the cylinder wall and the piston rings got scored . Very pricey lesson .
They do make a starting spray fluid especially for two strokes . It must say so on the can

I did not know that and I guess I've been lucky the times I used it.

 

[rgranger]

The expense was shop time for the mechanic to tell me nothing was wrong with the engine and shop time and hose for the new fuel line.

https://defender.com/assets/pdf/trident/uscg-fuel-hose-ratings.pdf

Helpful, thnx

I had a similar experience with a fuel line and a mechanic. I had spent a few weeks worth of evenings getting my Balboa 26 ready for a long-ish cruise along the NC coast. I had purchased some new fuel line... hung it in the shed on a Wednesday, and on Thursday installed in on a Honda 9.9. On Friday I drove 5 hours to Oriental NC for a 10 day cruise. Launched and but my engine would only run for about 90 seconds and stall.... reapeated this several times and then returned to port. Found a local mechanic and after several boat bucks he found a mud daubler had laid an egg in my fuel line... must have happend that Wednesday night it hung in the shed. Nothing wrong with my engine.

 

[capta]

If it was my engine, I'd remove the carb & plugs and fill every area in the engine including the lower end, with diesel fuel. Let it sit as long as you can, but at least 3 days. Turn the motor over now & then, re-adding diesel as necessary. Diesel is a wonderful cleaner and roughly 4% motor oil, so it lubricates as it cleans.
The carb can be soaked and cleaned in kerosene, or one of the commonly available carb cleaners. Take note: Take note of the number of turns you unscrewed the needle valves. That at least gives you roughly the same settings as when it last ran.
I'd spray the block with PB Blaster and all electrical parts with Corrosion Block. I would also, without fail, coat every nut/bolt you took out with an anti-seize.
Don't forget to replace the diesel with the proper lube for the lower end. I would also replace any seals that are available.
Of course, all that falls into place behind, "if it ain't broke, don't fix it!". I learned that one the hard way, several times

 

[Benny17441]

Pull the spark plug ( get a replacement) and pour some oil down into the cylinder and let it sit for 24 hrs. Pull on the starter cable slowly to see if it turns or if the piston rings are stuck to the cylinder wall. If stuck get some penetrating oil and repeat the flush. Once the engine is turning test for an ignition spark. Once you confirm you have a spark remove the carburetor and rebuild or replace. (they get gummed up and the seals deteriorate). Empty the old gas can and make sure is clean and add new gas with 2 stroke oil at 50:1. If the engine shows compression and you have a timed spark with fuel it should start. Adjust the carburetor and idle speed and you should be good to go.