1983 Mercury 115 hp 2-stroke in-line 6

[ahobbes]

Hello everybody,

I recently purchased a 1983 Baja 16SS with a 1983 Mercury 115 hp 2-stroke in-line 6. I know nothing about everything but I am an engineer so let's hope that gets me somewhere.

First of all, sorry if this is the wrong place for this post or my ignorance annoys you.

All of my questions concern the engine which I believe is a 1983. The serial number is 6263822.

Cosmetically, the boat and engine look beautiful. Underneath the engine's cowl is nothing but clean, shiny blackness. No oil or gunk anywhere. I was told by the seller that the boat had belonged to a rich lady who only took it out occasionally (once or twice a year) to entertain her lesbian friends (his words). She had it garaged otherwise. The seller also had it garaged and he says it was regularly maintained by his boat mechanic. I believed him (we had a few beers). So, 2 owners only.

I am going to assume I know nothing about this engine and so I will perform maintenance as such:

1. Replace impeller and lower unit oil (with Mercury High Performance Gear Lube SAE 90?). Check condition of lower unit internals.
2. Grease drive shaft with engine spline coupling grease.
3. Grease other things with other greases?
4. Drain gas tank (guy said he took it out last season and stabilized the gas but I'll replace it anyway, he also said he used a 40:1 mixture. I thought I was supposed to go 50:1? I guess since this is an older engine I should go with more oil. Also, I am at 5000 feet. Which gear oil should I use, the guy included a couple quarts of royal purple and one of the mercury brand stuff?)
5. Install an inline water separating fuel filter. Anyone know of a good one? (per Dr. Frankenmerc)
6. Fuel additives such as Star-Tron or Stabil Marine every tank? (per Dr. Frankenmerc)
7. De-carbonize with Sea Foam.
8. Change spark plugs.

Those are all of the things I would like to do but I am considering replacing the gas then starting it up just to see how it runs before I perform all of the other maintenance. Is that a bad idea?

That's all for now, I have about 9000 other questions but I'll have to ask as they come up. Thanks everyone for your help! Excited to finally be a captain of my own starship.

- Alex

[CNC_Guy]

I would replace fuel and start it, just to see if it runs(with water at all times). You're other steps seem reasonable. The gearcase oil, pick 1 and keep checking level often, r & r once a year minimum. Merc hi po oil or quicksilver is at wally world cheap. Just use quality lubes and be consistant. 50 to 1 is ok for that motor in normal operating conditions.

[CNC_Guy]

The Merc fuel filter/separator is fine, don't know part number. Filters also at wally world.<iframe id="google_osd_static_frame_2537586348491" name="google_osd_static_frame" style="display: none; width: 0px; height: 0px;"></iframe>

[ahobbes]

Thanks Dave, I gotta go checkout wally world for marine stuff, I generally avoid the place but I'm feeling adventurous.

I guess I'm just worried I'll touch this motor and it'll blow up. Gas is drained and I think I'll go with 40:1. I'll mix it up tomorrow and see how she runs. Maybe I'll take a video...

[NY Switzer-Head]

Inlines last nearly forever on 40:1. Keep the lube filled with Merc Hi-po. Wally world is usually cheapest around here. Run 91 non-eth if you can. I'm not sure about any problems at 5000'..... But long term issues on inlines seem to be crusty wires starting fires, and top crank seals dry and crack and let air leak in, causes lean out in top cylinder, eventually melting that piston. The only other piston you ever hear of going is #3, but I don't know why. Change the gear oil, grease everything, and do the water pump impeller every year. Impeller wear plate and housing if they show signs of scoring. Do NOT lug that motor by over-propping or over loading. Let it spin up above 5500 at WOT.

There is an inline group to join on here and on facebook. Both have some guys with a wealth of knowledge and TONS of experience. Have fun!! Great boat and motor to get into boats with!

[ahobbes]

Good to know, Greg. I'll be keeping it at 40:1 but also checking the spark plugs. I found a place in town that sells 91 non-eth ($3.90 a gallon! I'll have to check the 2 other places in town, found em on pure-gas dot org). One thing I've been wondering about non-eth gas, if I use it I need to be sure to get a water separating fuel filter (don't have one atm) because there is no ethanol to absorb any water in the system, correct? Although, I don't really see how water will get into the system unless my seals go bad.

The wiring looks to be practically brand new but I still need to inspect deeper toward the transom. If the condition of everything else is any indicator I bet the top crank seals are fine but that said things get pretty dry here in Colorado, not sure if that is a factor or not in the condition of those seals. Maybe salt is more of a concern there.

What do you mean by "Let it spin up above 5500 at WOT"? Sorry, I still have yet to understand how prop size, loading, trim, etc. affect RPM and what range to keep RPM in.

There do seem to be a lot of experts around online, that's fortunate because there are none in Colorado that I know of!

Thanks again!

- Al

[NY Switzer-Head]

A fuel water separating filter never hurts. Cheap easy insurance. WOT= wide open throttle. With your boat loaded how you will use it most, it should be propped to run above 5500 RPM at WOT with motor trimmed where your top speed is fastest. These motors don't like to be over loaded at WOT (like you can't get it past 4700-4800 no matter what you do). They will start melting pistons and you will see little balls of aluminum on the plugs. You can't really over-rev them. Up to 6000+ they are fine bearing wise, but usually run out of air flow around 5800. In my experience, if you prop std load to 5500, and decide to lighten it up and do an all out max speed quest, you'll be right near that 5800 mark. Non-Eth is $5/gal here until you get 25 or so miles from the lake. That altitude you may be running rich and not getting all the power, but that's better than lean!! Try the folks on Facebook about that... Probably just leave it alone unless you have issues. Watch that top plug.(all of them really) It will tell you if something goes wrong with that seal. Have fun!!

[NY Switzer-Head]

The stator wires are notorious for issues. There is a guy on ebay who rebuilds them real nice.

[Glasstream15]

My 1986 InLine has run 40:1 Quicksilver Premium+ since I bought it new. Check Timing if you can and make sure it's not over 21 degrees wide open. My motor has been propped to turn 6200 with a light load since new. Normal fish load I get about 5800. 1987 Glasstream 15V and light I get right at 60 MPH. Only problems I have had were the exhaust baffle, common on InLines, and Idle Stabilizer nearly cost me a piston. It's a little box mounted on the front cowl support with a couple of wires. Throw it as far as you can, or the nearest trash can, and tape off the wires. That thing has destroyed more motors than just about anything you can name. Great motors, lots of life and decent performance for the size of them. Enjoy. and enjoy that unique InLine sound.

[NY Switzer-Head]

My 1986 InLine has run 40:1 Quicksilver Premium+ since I bought it new. Check Timing if you can and make sure it's not over 21 degrees wide open. My motor has been propped to turn 6200 with a light load since new. Normal fish load I get about 5800. 1987 Glasstream 15V and light I get right at 60 MPH. Only problems I have had were the exhaust baffle, common on InLines, and Idle Stabilizer nearly cost me a piston. It's a little box mounted on the front cowl support with a couple of wires. Throw it as far as you can, or the nearest trash can, and tape off the wires. That thing has destroyed more motors than just about anything you can name. Great motors, lots of life and decent performance for the size of them. Enjoy. and enjoy that unique InLine sound.

What he said!! Forgot late models had that pesky stabilizer! Junk it!! NOW!!

[ahobbes]

Hey guys,

Thanks for all the info, it's really valuable. I'm gonna come back at ya guys with questions regarding the idle stabilizer, etc. but right now I need some help with this puppy...





Yeah, just got the lower unit off, went pretty well. I'm surprised to see so much sand in there. How should I clean it out? That is just an exhaust port, correct? Can I just hose it out? Also, I'm not sure what the shifter seal should look like. Anyway, I'm gonna go eat some pizza and perhaps I'll get a response while I'm gone!

Thanks again!

- Al

[ahobbes]

Went ahead and hosed everything out, got it all nice and clean then installed my new impeller, gaskets, etc. Started it up and immediately got a solid stream (might have been primed from previous runs though). One thing I can't quite get the hang of yet is how to start the engine without flooding it, I guess that's how it goes with engines that are new to you, just gotta figure out what operation works best.

I checked out wally-world and they did have the fluids/greases I will be needing in the future, excellent. I still couldn't find a fuel filter though. Does anyone have a link to a reasonably priced fuel filter that will be compatible with the fuel lines on my 1983 Mercury 115? Looks like 1/4" is pretty common, I think that's what I have. Do I need to install some sort of fitting onto the fuel line to screw onto the filter ports?

Greg, when you said watch that top plug you mean look for balls of aluminum (which means the piston is melting and the seal is letting air in leading to a lean condition in that cylinder)? I'll keep my eye on the RPM, maiden voyage today!

GlassStream15 (and Greg), I have been researching a bit on the Idle Stabilizer. I don't know how to check the timing but I'm sure it's something I can figure out. I should probably do that before and after removing the Idle Stabilizer, right? Due to the fact that I am still rather ignorant regarding the expected/correct behavior of this motor, I might wait a little while to remove the stabilizer. Hope I don't regret that decision! After removing it, will I need to pay special attention to certain behaviors (such as idle)? Or make further timing adjustments? (I have found answers to these questions on the idle stabilizer threads but I wonder what your experiences are.)

Oh yeah, one more question. What is the hose/tube that comes out next to the shifter linkage (see bottom pic above, just to the left of the shifter linkage spindle thingy)? It seems to go nowhere, is it just a vent?

[milkdud]

One thing I can't quite get the hang of yet is how to start the engine without flooding it

Inlines are hard to flood. One common complaint is they are hard to start. They normally take lots of priming and tight choke shutters to start right off.

If your flooding it. I would assume the needles are not working proper and letting gas by.

That little line is for a Speedo. You can hook up a speedometer to that and there is a little hole on the front of the case to pick up water pressure.

C

[Glasstream15]

This might help you out some: Manual specs are different for each but this is close enough to get them all REAL close. This assumes nothing is broken or "wrong" with it. This also assumes that the timing pointer is properly adjusted (if adjustable) to accurately read TDC of the #1 piston.This basic procedure will work for all the 2/3/4/6 cylinder inlines from 1960 to 1988. It's not for the newer 3 and 4 cylinder loopers.Engine offDisconnect throttle cablePull throttle arm to full throttle and verify carbs open fully. Adjust main throttle stop so that the carbs are JUST hitting thier own little throttle stops. The idea here is that you want the screw stop and NOT the carbs acting as the "final stop" for your throttle lever.Return the throttle to idle, carbs should be closed. Set all idle screws to 1 3/4 turns out from lightly seated.Remove all plugs except #1, hook a timing light to #1. Then follow the narritive.When the throttle is in the idle position the carbs should be fully closed and the ignition retarded. It is the amount of retardation that determines your idle speed and is set later with the idle stop screw. Timing Event One - throttle pickup.As the throttle is advanced, the spark timing advances toward TDC and then to before TDC. As the timing is just passing TDC the 1st (minor)throttle pickup should hit and start to open the carbs. Use the timing light. Adjust the tang or trigger screw to make this a reality. All of them are speced different, but if the 1st pickup hits at 3-4 degrees BTDC advance - you win. Use the timing light with a friend cranking it to complete this setting.Timing Event Two - max advance.As you continue to advance the throttle the timing will advance while the carbs slowly open a bit more. The next adjustment is max advance, this is the point where the distibutor (or trigger) can advance no more. Set the max-advance stop to 21 degrees for "direct charge" crossflow inlines and 34 degrees for the older plain vanilla crossflows. Use the light, - err to the side of caution.Right after max advance, further throttle motion should cause the second throttle pickup to hit and open the carbs to full. You already set that -now verify it.Leave the throttle cable disconnected and go to the water. Leave the boat strapped to the trailer and back it in so it's deep enought to run. Have a friend crank it while you operate the choke and throttle. Warm it up at 1500 rpms's.When "warm" adjust the idle stop screw for about 800 rpm and then ajust your idle needle(s) in (one at a time) till the motor stumbles. Quickly backing it out 1/2 turn from "stumble" will usually save it from needing a re-start. Do that for all the idle screws. Re-set idle stop for 800.Now have your friend put it in gear (make SURE you are on the transom NOT in the water) and reset your idle stop for as low as you can get it. 500-600rpm is great if your old reeds will let it idle that low in gear. Now, re-adjust the idle screws, in to stumble, then 1/2 turn out. When you've gone back and forth with that a few times and have it "perfect" - adjust each one out 1/4 turn.Reset the idle stop so that it's about 700-800 out of gear and 500-600 in gear. Sometimes bad reeds won't let you get that low, you've GOT to get it under 1000 in neutral (worst case) to avoid beating up your lower unit when you shift into gear, even 1000 is "bad" but like I said "worst case".Now adjust (and hook up)the throttle cable so that with the shifter in neutral, there is light to moderate pressure holding the throttle arm against the idle stop.Take the boat off the trailer and go out in the water. Try the hole shot. If it falls on it's face try adjusting the idle screws out 1/4 turn at a time (all of them together) till you can get a hole shot. You can kind of do this on the trailer at the ramp, but it's not really safe for you, the boat, or the tow vehicle.You're done.

[Glasstream15]

Hope this helps some too. I'll have one more.