Looking for advice on preparing my engine for the new year

I have a 1994 Mercury 115 and haven’t had the boat out for 4 years. I plan to bring it to a repair shop to have it made ready for the new year, because I plan to do a lot of fishing this summer. I know nothing about engines. I assume I’ll want to replace the fuel filter and fuel pump. Probably the hoses, a friend told me to replace the impeller (I don’t even know what that is). I’m looking for suggestions from you guys, and I’m going to make a list of your responses and give it to the repair place.

First and foremost you must have the boat’s fuel tank pumped out and flushed. Anything you do to the engine will quickly be undone if you try to run it on the old fuel that’s left in the tank. The fuel in those tanks has most likely gone bad and it will cause constant problem if you try to use it.

Once you’ve had the tank pumped out and flushed, only put a small amount of fuel in the tank for testing purposes. There may be residue or varnish that comes loose in the flushing process and you don’t want to have a large amount of fuel that then has to be pumped out again to fix the problem if it occurs.

Unless you’ve been very diligent about maintaining it, the boats battery is probably bad. I would have it tested and replace if necessary.

The impeller is the part that brings cooling water from the lower unit to the engine. This is a critical part and overtime they wear and become brittle. Absolutely have it replaced.

Change the lubricating oil in the lower unit. This is a very simple process and you could easily do this part yourself. But since you’re taking it in anyway it probably makes sense to have the mechanic do it.

On the engine itself I would replace the fuel filter, the spark plugs, and have a general inspection done. I would also have the cylinders fogged with fogging oil before attempting a restart. This will lubricate the cylinder walls in case they have dried out while the boat was not being used. Some will say this is unnecessary but I would not take a chance at scuffing the cylinder walls.

I would not have the fuel pump done as a matter of general maintenance. I would try a restart before and find out if it’s working. If it’s working leave it alone.

Anything else that needs to be done should be dictated by what happens when the mechanic attempts to restart the engine and tank test it. I would not do anything else other than the above as a matter of routine maintenance.

Grouse

94, I assume carbureted? If so, minimum of bowl and jets cleaned.

IMO you have 3 options…
1)Complete engine overhaul which will be very spendy but you’ll have a like-new motor that will “probably” be trouble free for years to come but more importantly make your worry free on the water
2)Buy a new motor. More money but you’ll get many many years out of it. If you really like boat and have no issues with it, might be a great option.
3)Replace all fluids and let’er rip! Similar to what Grouse suggested but I wouldn’t fix anything mechanical, like impeller, unless I know it was having issues…I guess spark plugs are pretty cheap but honestly they can run for YEARS. Complete fluid swap you can do and would be cheap. I’d take it out on first ice out a few times and see how everything runs.

What ever you feel comfortable with. I’m a #3 guy cause I hate spendy money if I don’t need to. Over the years, I’ve learned “most” maintenance items tend to slowly show their in need of fix and don’t just “stop” working…most of the time.

In my experience, the engine will probably fire up and run just fine. The key is to absolutely avoid sucking a bunch of the old, bad gas and chunks of fuel tank varnish into the engine when it is restarted. That’s why I say #1 is to pump out the tank and dispose of the old fuel.

Let the mechanic figure out what really needs to be done. If the carb needs cleaning, so be it, but why run up the tab with a list of stuff that has no benefit unless it needs to be done? If it ain’t broke, don’t fix it. A good hard Italian Tuneup (3 laps around the lake at full throttle) is all most engines need to clear the throat.

IMO, guys tend to way, way, way overthink stuff like this. 2 strokes are tremendously durable and infinitely serviceable. I’ve restarted all manner of outboards and other small engines that have been collecting dust in a garage for years or even decades with nothing more than fresh gas/oil.

Grouse

Thanks for your help. I’ll take your advice and not go crazy with things that don’t really need to be done. Although it’s an old engine, it really has a low amount of hours on it. I’ve had it since 2002 and have probably only put 100 or so hours on it. It ran fine last I used it, so other than the gas issue, I don’t think there should be any trouble. I’ve already bought a new battery, cuz the old one was torched.

four years is a long time for rubber/neoprene components to sit,this includes hoses,pump impeller,and fuel pump diaphragms/gaskets.

lets start with hoses,the one from the tank to the motor if four years old or older,replace it,no question especially if its original.

the next hoses to check are the main bearing drain hoses,they run from the upper main bearing down to the center main bearing and then to the bottom main bearing.
they have a nasty habit of breaking/splitting right at the barbed fitting.
when they do,the engine will go lean and fry a cylinder.
the middle and lower bearing drain hose is behind the ignition module and it needs loosened and pulled out of the way to check them properly.
check the remaining fuel hoses for soft spots or cracks,replace as necessary.

fuel pump ,it has three things to battle with during its life span.
one is fuel on the pumping side,second is the side that is pulsed by the crankcase pressure/suction cycles,combustion byproducts and bad fuel will weaken the material it is made of over time and it will stretch the diaphragm enough it wont pump enough fuel to keep the carbs full,engine goes lean and you end up with a junk engine.
the third thing a pump faces in its life is the check valves failing for what ever reason,a good example is the fuel hose coming apart and causing them to stick open,I have pictures if you want to see what I mean.
repairing/replacing the pump is a must do.

the impeller,as stated is in the lower unit,I would highly recommend replacing it without question due to the fact that sitting for four years alone it has most likely taken a ‘set’ and the impellers legs wont flex enough to pump water effectively which will cause the motor to run hot,especially the upper cylinder,piston scuffing/scoring can and will occur if ran too long that way.
another problem that I have seen countless times is the impeller legs coming apart and plugging the water inlet at the base of the engine,this restricts the flow of water even with a new impeller if not checked and removed when the impeller is replaced.

on the subject of cooling,pull the thermostat and make sure it is not plugged shut or stuck open.

carbs,even if the engine was winterized properly I would remove them and have them cleaned as any fuel left in them has turned to gum by now and will give you fits or a toasted motor from running lean.
as Grouse stated,clean and flush the entire fuel system,tank included.
install a water separator/filter between the tank and engine if it doesnt have one now,cheap and easy to do and will save you problems down the road,er,uh lake.

spark plugs,they are cheap enough,put a new set in and start from scratch,make sure to NOT use restrictor type plugs in that engine,I had to learn the hard way years ago,take it from me.

one last thing I would recommend,until you know for certain the oil pump is working and the 2PSI valve is letting oil through,I would mix the first tankful of gas at fifty to one,this will not hurt a thing.
the 2PSI valve is located between the pump and the carbs,it is a brass check/pressure regulating valve.
if it has failed from a broken spring or a chunk of gunk and sticks open the carbs will overfill with oil as quickly as overnight,its symptoms are very hard prolonged starts that end up being very smoky and a rough running engine until the excess oil is cleared from the carbs.

if that 2PSI valve is stuck shut,little or no oil is allowed to reach the engine and it wont run very long without oil and end up being junk,hence the recommendation of mixing the first tank of fuel so that you can see if the oil reservoir is being emptied indicating the pump and valve is working properly.

any more questions,pm me,I will give you my email address and phone number and walk you through most things.
if you take it to a reputable shop which I highly recommend if you are not the least bit capable,you can still contact me with questions.

run non oxy gas and good two stroke oil and you will get along fine.

tight lines and happy boating !!

Thanks Iowaboy. I was hoping you would respond to my post, since you really seem to know what your talking about. I’m going to print your response, and hand it directly to the mechanic who will be doing the work.

you are welcome Chris,dont take any of it as trying to scare you with my reply.
I have worked on mercs,chryslers,johnson and evinrudes for a long time now and know what to look for.

I dont have a list of repairs for your motor since it was new,nor do I have a crystal ball to see whats going on with it now.
but if you check out everything I listed you will have a safe and reliable outboard that should serve you well for many years to come.

nothing worse than get it running with just the basics and out on the lake five miles from shore and it quits on you.
sometime remind me to tell a story of the very first outboard I ever owned and got running when I was thirteen years old.
it was an old scott-atwater five horse,learned a ton the first day,er,uh,ahem,fifteen minutes out.