Having bought ANOTHER boat–a 1985 Bass Tracker–I promptly set about refurbishing it. Unlike the previous two, this one had been partially restored by a previous owner.
As I’ve mentioned, I didn’t agree with all of the decisions made along the way. The bright blue marine carpet, for example, was a bit garish for my tastes.
More importantly, the boat was underpowered: unless you’re in no hurry, a hull weighing 840 pounds needs more than 25 horsepower to push it.
Although I was tempted, the cost of a new engine far exceeded my budget. So it was that I entered the brave new world of used outboard motors.
*****Two things to consider before you buy an older motor: some repair shops won’t touch them, and replacement parts can be hard to find.*****
I went to a marine engine repair place downtown and checked out their boneyard. The man there steered me to a 2003 Johnson 50 hp two-stroke which he assured me “ran great.”
A prudent man would’ve requested a test run, but in my excitement I agreed to his asking price for the motor, plus nearly the same again to install it on my boat (and to bypass the original oil mixing system and its expensive components).
He also offered to sell my old engine on consignment (it’s still there, if anyone’s in the market for a gently used Yamaha 25).
I dropped off my boat and received a firm promise that it would be ready the following week.
It sat on their lot, untouched, for a month until my increasingly urgent pleas finally spurred them into action.
They rushed to install the motor last thing on a Friday afternoon, but discovered a broken steering link and had to wait another week for a part. At last they called to tell me it was ready.
The boat was littered with bits of wire insulation and the carpet was covered with marine grease, but I finally had a new–new to me, that is–engine.
The test run at home was promising, so I took it to the lake.
The motor worked OK at the lake, but it was hard to start and occasionally ran a little rough.
When I got it home, there were green and black fluids leaking from the engine.
That couldn’t be good, could it?
I had no idea.
By now I was somewhat leery of the original shop, so I called around. A reputable establishment on my side of town agreed to take a look at it, but informed me they were scheduling nine weeks out.
It was time, I decided, to take matters into my own hands. I knew absolutely nothing about outboard motor repair–but that was about to change.
(cue ominous music)
Unskilled mechanic
I searched the internet for a Johnson service manual but couldn’t find one, so instead I ordered a Clymer shop manual that covers dozens of models, including mine.
Internet critics disparaged both the Clymer manual and its SELOC counterpart, but I figured any information was better than none.
(note: some of these are affiliate links, which means that if you click the link and buy the related produce, the vendor may pay me a fee. Your price is unaffected)
The manual was laid out awkwardly. I found the solution was to flag sections that applied to my motor so I could refer back to them without paging through a bunch of irrelevant material.
I backed up my book study with YouTube videos, by far the most helpful of which were provided by Stu of Dangar Marine, based out of Dangar Island, New South Wales, Australia. I would’ve never had the courage to undertake this project without those videos.
Once I pulled the cover off the motor, the source of the green fluid leak was obvious: there’s a hose (part number 35 in the illustration below) that drains unburnt fuel from the intake air manifold to the lower engine manifold–or there’s supposed to be. Mine was missing (apparently the mechanics that installed the motor didn’t notice).
I cut a piece of rubber fuel line to fit and clamped it in place.
The black fluid leak was more worrisome: it was coming from the lower unit where the water pump, gears, and propeller drive shaft are located. After a panicked internet search, I discovered that it was probably just a combination of unburnt fuel and exhaust residue.
There’s a rubber relief grommet on the back of the engine that’s supposed to vent excess exhaust overboard, rather than allow it to condense into black goo and drip down into the lower unit. Mine was in tatters and barely held together when I pulled it off.
I went to MarineEngine.com (because they tend to have the best prices) to order a replacement but discovered that tragically, that part is no longer available.
Note: Crowley Marine is another great option and often carries items the others don’t. You really can’t go wrong with either.
I ordered a 3D printed version which looked great but turned out to be too stiff for me to install. I was also unwilling to pay $80 to a part search service for an OEM replacement.
Fortunately, I found a video on the “Sweet Project Cars” YouTube channel that explained how to repair old rubber using super glue and Permatex silicone adhesive sealant.
Worth a try: since it would be on the exhaust I wasn’t worried about it coming apart and going into the motor.
After letting it dry for a few days I wiggled it back into place. So far it works like a champ: excess grunge is now vented overboard and the leak has dried to a trickle–mainly when I spend a lot of time at idle.
The plot thickens: cooling issues
Up to now my “repairs” were trifling affairs that required no mechanical skill whatsoever: convenient, because I possess no mechanical skill whatsoever.
However, during a subsequent test run at home the water coming out of the telltale slowed, then stopped. Fearful of overheating the motor, I shut it down and hurried inside to research the problem.
The internet consensus was that either a) the water pump was failing, or b) something was blocked.
Since I had no idea when the water pump had last been worked on, I ordered a replacement kit.
Living on the surface of the sun as we do here in Phoenix, I figured a functioning engine cooling system was important.
I removed the lower unit following the instructions in my manual, then carried it into the garage.
There are dozens of videos on the internet about replacing Johnson/Evinrude water pumps (Johnson and Evinrude merged in 1936). After watching most of them, I replaced the impeller and other key components without incident.
The water pump looked good even before I worked on it, so I didn’t think it was the problem.
Before replacing the lower unit I decided to blow out and backflush the engine cooling system in an attempt to remove whatever was blocking the telltale. This involved squirting compressed air and then water through the telltale and, while I was at it, through the thermostat port.
I didn’t know when the thermostat had last been replaced, either, so I ordered a new one.
Imagine my surprise when I removed the thermostat cover and discovered–nothing. A previous owner had apparently opted not to replace his thermostat.
I ordered springs and other missing parts, then flushed the telltale and cooling jacket.
When the parts arrived I replaced the missing thermostat, put on a new gasket, and reinstalled the cover. Everything worked again and the new seals held water.
Hard starting
Now that the telltale was working again, I focused on why the engine was hard to start.
It ran OK after starting, and once warm, restarted easily. I researched “cold start problems” and decided that the fuel priming solenoid–which is supposed to work when the ignition key switch is depressed and the motor is cranking–wasn’t.
I ordered a replacement and installed it, sealing the connections to prevent shorts.
With the new primer–and better use of the “fast idle” lever–cold starts were no longer a problem.
Victory!
While researching my cold start issues, I noticed that the engine didn’t seem to be charging the battery at all. I put a multimeter across the battery terminals and confirmed that there was no increase in voltage, even with the engine revved up to high idle.
I assumed that the engine’s AC power source–the stator, a system of magnets and wire coils under the flywheel–was fine since I had good ignition at the spark plugs.
The battery was also fine.
I decided the culprit must be a bad rectifier.
A rectifier’s job is to convert AC power from the stator into DC power that can charge the battery. I replaced the old, generic rectifier I’d inherited with a (much more expensive) CDI Electronics part.
I was learning that cheap, knockoff components were apt to fail quicker, and that spending extra for a quality part might save me both time and money in the long run.
I put the multimeter back on the battery and found that I was now getting a slow voltage rise at high idle. Problem solved!
Running rough? Check the basics.
Since this was my first two-stroke engine, I didn’t know if the raggedy idle I was hearing was par for the course for these old motors–even after listening to dozens of internet samples.
Either way, I wanted to tune the motor to its best potential.
I decided to check compression in the cylinders to make sure the engine was sound before investing too much more time and effort.
I ordered a compression tester and hooked it up: both cylinders tested good, within 10 psi (121 and 129) of each other.
I double-checked the ignition system with a spark gap tester: the spark from both leads easily jumped a 7/16″ gap per factory specs.
The plugs themselves were gapped correctly at .030″ but were somewhat oily, confirming my guess that the motor was running a little rich (fuel-to-air ratio was high).
I installed a new set and set the oily ones aside as spares.
The last thing to check was fuel.
I found a small leak in the line out of the new fuel pump the mechanics had installed: I trimmed off the offending end and reseated it, securing it with a new zip tie.
The rest of the fuel system looked good.
Tune up
The first step in the manual for engine service is to spray engine tuner into the carburetor intakes.
You run the engine until it’s warm, then spray half a can of this stuff into each carburetor. When the can’s empty, shut down the motor and let it sit for “3 to 16 hours”–I waited seven–then restart the motor.
Be prepared for billows of caustic smoke and greasy residue from the exhaust as accumulated impurities burn off. My engine actually “dieseled” (ran with the key off and spark plugs disconnected) briefly as the deposits burned.
The next step was to remove and clean the carburetors. I was thoroughly intimidated by the prospect, but “Dangar Stu” has a video that walks you through the process step by step.
I ordered two carburetor kits from MarineEngines.com and got to work.
These carburetors come off easily: first, disconnect the throttle link…
…then remove the fuel lines from the top (primer) and bottom (main)…
…and finally, unbolt the two 1/2″ nuts holding the carburetor to the engine.
After removing each carburetor I peeked into the engine to check reed valves, making sure none were bent, broken, or missing.
I carried both carburetors into the garage and took them apart per the Clymer manual/Stu’s video.
I found a mangled high speed fuel jet in one bowl that had to be drilled out and replaced, using a handy extractor set I ordered online.
An intermediate air bleed jet in the other carburetor was clogged, but a can of carb cleaner and some brushes cleared it up.
I gave everything a thorough scrubbing then put the carburetors back together, replacing gaskets, seals, and other consumables with parts from the kit.
I agonized the most over setting the floats, but in the end it was fairly simple: when inverted, the float will be within specs if it’s parallel to the carburetor body.
When upright, the float should hang down between 1.125 and 1.625 inches from the carburetor body. The old ones exceeded that by quite a bit but didn’t seem to bind at all.
Nonetheless I followed instructions and bent the little tabs on the back of the floats until both extended about 1.4 inches.
I bolted the carbs back onto the engine and reconnected fuel lines, replacing the clear one I found on the top carburetor with official black rubber 3/16″ inner diameter line. I secured them all with zip ties, then pumped the fuel bulb to check for leaks.
Link and synch: preliminary settings
I set the idle speed stop screw (a) and carburetor mixture screws back to factory specifications, and disconnected the throttle control cable (b).
Then I made sure both carburetors opened at the same time. To do this, first loosen the screw on the top carburetor linkage arm and let both carburetors snap closed.
With both carbs fully closed, hold a slight upward tension on the upper carburetor linkage arm to take out the slack and re-tighten the adjustment screw.
Now loosen the linkage arm adjustment screw on the bottom carburetor.
Move the throttle cam follower and the throttle cam together so they touch at this mark.
Hold them together while you re-tighten the adjustment screw.
After tightening the adjustment screw, move the throttle cam back to idle. There should now be a .020″ gap between the throttle cam and throttle cam follower.
As you advance the throttle, the follower “picks up” the throttle movement after that .020″ gap closes and the carburetors will start to open.
If need be, you can adjust the gap by popping the end of the throttle control rod off, twisting it in or out to slightly change its length, then popping it back on.
Now that the preliminary idle settings are done, adjust the wide open throttle stop screw, below, to make sure the carburetors open fully when the throttle is all the way forward.
The shaft roll pins on the left side of the carburetors (see diagram below) are vertical when they’re fully open.
Now you can hook the engine controls back up.
In my case, easier said than done…
After a struggle I discovered that my pickup roller and throttle cam roller were the wrong size: the clear Teflon-looking outer layer was missing on both.
The resulting slop explained the “dead zone” I felt accelerating out of idle and the engine’s reluctance, once advanced, to fully retard to idle.
I ordered replacements for both rollers. When they were in place I went back and adjusted everything again, then connected the throttle cable per the manual.
It was much easier this time.
To adjust the throttle control cable, remove the cover (a) and lift the cable adjustment barrel out of the pocket underneath.
Set the control handle just forward of neutral, then pull forward on the throttle cable (b) until the tension holds the idle screw against the stop.
Twist the adjustment wheel (c) to maintain that tension, push the adjustment barrel back into its pocket, then replace the cover.
You’ve tightened it enough if the idle screw returns to its stop when you move the fast idle lever forward and back to idle.
If you tighten it too much, it may be hard to move the controller handle into forward or reverse.
“Fine” tuning
The idle mixture screws (aka “slow speed needle valves”) in both carburetors had been damaged at some point by over-tightening, so I ordered new ones.
The crimps in the old screws meant that you were dealing with binary adjustments: you got either not enough fuel for a given amount of air, or way too much. I hoped to do better with the replacements.
From the factory setting (3 1/2 turns out from “lightly seated”) I backed both mixture screws out an eighth of a turn at a time until the engine began to bog and run rough (too rich), then I tightened them back in until it began to shake and “sneeze” (too lean).
I split the difference between the two extremes which gave me the fastest, smoothest idle. Then I backed each mixture screw out one more eighth to err slightly on the “too rich” side.
I checked idle spark timing with my new induction timing light. On this engine, the spark plugs are supposed to fire when their piston is between zero and two degrees past top dead center: they did.
You’re also supposed to check timing at wide open throttle to ensure the spark advances enough to compensate for the increased piston speed.
However, I don’t fancy hanging over the engine with a timing light as we bounce across the lake at full throttle, so I’ll leave that for a real mechanic to check (in a tank, with a test prop attached).
Finally, I backed off the idle screw, lowering idle RPM below 1200 as measured by an inexpensive induction tachometer.
I figured with the air manifold and engine cover back on the RPM would drop further, and with the boat in the water, in forward gear, at idle, it should be closer to the 800 RPM the manual calls for.
New prop and bling
The prop that came with this motor had lower pitch than the original and was pretty banged up, so I ordered a replacement that matched factory specs. The first one I received was defective but the vendor quickly replaced it.
I installed that one and kept my banged up original as a spare.
The paint on the motor held up well so, despite my normal inability to leave well enough alone, I’m going to do just that.
The placard on the back of the cowl, however, had seen better days, so I broke down and ordered a shiny new one.
Time to get back out on the water for more testing.
Doing my own repairs has taught me a lot about this motor and saved me money, too (assuming it doesn’t explode).
Now that it’s running better, I’ve got my eye on a fancy new tachometer:
It won’t change how the engine works, but like a new pair of tennis shoes, it’ll make me FEEL like I’m going faster.