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  Johnson c.1997 48-HP Runs Poorly

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Author Topic:   Johnson c.1997 48-HP Runs Poorly
minimontauk posted 09-05-2004 08:11 PM ET (US)   Profile for minimontauk   Send Email to minimontauk  
I have a 1997 [Actually the author wrote he had a 97'--that is ninety-seven foot] Johnson 48-HP outboard motor without VR0 system on my 87' [Again, got that apostrophe in the wrong place--so much easier to just write out the year in four digits, but instead we got us a 87-foot long] 15' Sport CC. Bought it used, looked very well maintained. Had it professionally tuned up and gone over this last spring. Repairs as follows:
--New fuel pump
--new plugs and wires
--new waterpump
--new starter
--and a full tune-up.

Had a high-speed stall problem that stopped after tune-up and fuel pump. Ran (well) all summer, now it suddenly started running intermittently on one cylinder, runs very rough, second cylinder occasionally kicks in. I ran it low speed all summer in the harbor, figured I had a fouled spark plug. Replaced spark plugs, no joy.

Is this kind of continual cycle of problems typical of Johnson motors?

Any suggestions as to what my problem may be? Frustrated to be dropping more money into a hole in the water.

13dave posted 09-05-2004 08:22 PM ET (US)     Profile for 13dave  Send Email to 13dave     
Does it happen to be a SPL model?
Sal DiMercurio posted 09-05-2004 10:44 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Yes a 48 special is a detuned 50 & the 88 special is a detuned 90 & I don't know that they acually detune them.
Those engines are built like a tank, probably one of the most reliable engines ever made.
Sounds like either a bad coil or power pack.
Sal
Peter posted 09-06-2004 09:02 AM ET (US)     Profile for Peter  Send Email to Peter     
I had a 48 SPL on my 15 Super Sport. As far as I could tell, the SPLs were not detuned as the one I had ran as fast as any 50 HP outboard. The numeric HP designation is within the 10 percent limits and it was just one of OMC's ways of differentiating between the low priced, no frills SPL models and the regular models. That motor's design has been around since 1970 or 1971 and outboards don't get much more reliable than that one. They do run a little rough at idle, however.

I agree with Sal's assessment. Most likely its a coil. I would get a replacement coil and swap out the coil on the plug that appears not to be firing. Replacing a coil is a fairly inexpensive, do it yourself repair.

WhalerGoFar posted 09-06-2004 02:09 PM ET (US)     Profile for WhalerGoFar  Send Email to WhalerGoFar     
I have a 1988 48SPL on my 17 footer and it pushes my wife and I along at 30mph and with an added doefin it jumps out of the water like a scalled dog. She has 150psi on both cyl's .

I agree with Sal also on the coil assesment. However I disagree on the "detuned" part. The SPL ment the motor does not have T&T...thats all and the 48..88..etc was marking tool to set them apart from the rest of the field.

I have a Clymer Shop Manual that I paid $35.00 for that I will sell to anyone interested for 20.00 plus shipping.


Mike
Naples, Fl.

13dave posted 09-06-2004 06:21 PM ET (US)     Profile for 13dave  Send Email to 13dave     
wow i alwasy thought spl was some sort of high torque sailboat engien, i based this asumption on the fact that the 28 has a very small lowe unit/ prop gapand propr spine similiar to that of a sailboat outboard.
minimontauk posted 09-06-2004 06:49 PM ET (US)     Profile for minimontauk  Send Email to minimontauk     
Thanks for the response. By "coil" are we talking about removing the flywheel? I think this motor has UFI ignition.That looks like a tough job with a flywheel puller. The "power pack" would be the widget the spark plug wires are connected to? Another sympton I noticed, with the engine tilted up, if I prime the fuel line bulb, raw fuel runs out of the engine housing from somewhere inside. Is this because the carb. floats are displaced? I though the float valve would prevent this, otherwise fuel could leak out whenever the engine is tilted up. Maybe a stuck float valve in one carb. is flooding one cylinder?
Peter posted 09-07-2004 12:52 PM ET (US)     Profile for Peter  Send Email to Peter     
No need to remove the flywheel. It is very simple to swap coils and it shouldn't take more than 5 to 10 minutes.

The coil is the black cylindrical shaped item from which the spark plug wire originates. There should be two of them. Chances are that one of your two coils is bad. If you trace the other wire to the coil it will lead you to the power pack. The powerpack is what the two coils derive their power and timing from. If the powerpack was bad, I believe that the engine wouldn't run.

Pumping the primer bulb while the engine is tilted will probably lead to fuel leakage out of the carburator bowl.

The 48 88 and 112 SPL models were low cost, no frills models (no VRO, no T&T). However, I believe you could get T&T as an option on the 88 and 112. Based on my experience, I highly doubt they would have gone to the trouble to "detune" 2 HP out of these engines.

The 32 cubic inch 28 SPL used the original 32 CI 25 HP's old fashioned lower unit that did not have the thru-hub exhaust (the 25 was introduced in 1977). It's not a sail boat lower unit, just a lower unit design that dates back to the 1950's.

ShrimpBurrito posted 09-07-2004 08:39 PM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
FYI, I have purchased after market ignition parts for my 1987 Johnson 40 HP engine from www.boatfix.com and have had no problems. They're made by Sierra, and Boatfix prices are very close to wholesale. I also have experienced very good customer service from them, and Sierra parts can be about 75% off OMC prices.
jimh posted 09-07-2004 10:09 PM ET (US)     Profile for jimh  Send Email to jimh     
What is "UFI Ignition"?
Sal DiMercurio posted 09-07-2004 10:19 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Good question Jim, I wondered that myself.
Sal
Bigshot posted 09-08-2004 12:10 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Hold up people...many things can be the culprit. Does it have spark on both cyls? If so then it "could" be the carb. There are 2 carbs on this engine, 1 for each cyl. Have you done a compression test? If not you might want to start there and make sure you still have a 2 cyl engine, then check spark. What does the plug look like? Is it wet or bone dry? Is it covered in water? Just because it is only running on 1 cyl does not mean you need to spend $200 in electronics that are NOT returnable. It could also be the trigger or stator assembly but not sure of setup on this puppy. Is ignition advancing all the way, etc.
TampaTom posted 09-08-2004 06:29 PM ET (US)     Profile for TampaTom  Send Email to TampaTom     
Didn't see spark plug wire mentioned. The OMC wire ends are a coil that pierces into the wire. Often they rip loose or no longer make good contact with the wire.
Check for spark on both plugs. If one is out, switch your plug wires and recheck.
jimh posted 09-08-2004 07:45 PM ET (US)     Profile for jimh  Send Email to jimh     
Changed TOPIC; was rather provocatively "Johnson Motors Unreliable?". Also, added a few parenthetical comments about misuse of the apostrophe as an abbreviation mark in contractions for dates. For some reason, the folks that think it is somehow more readable to write dates as three characters using an apostrophe and two digits always seem to get the apostrophe in the wrong place. It is so much more readable and less prone to error to just type that little bitty extra character and use four digits for the year date.

Also changed some typography to make it a bit easier to read --jimh.]

jimh posted 09-08-2004 07:55 PM ET (US)     Profile for jimh  Send Email to jimh     
On Labor Day we were in staying on the boat at the dock, and in the late morning a fella came down the pier with a brand new Honda 9.9 HP outboard. He was wheeling it on a fancy stand with handle bars and pneumatic tires, which was necessary because the thing looked like it weighed about 120-lbs.

A couple of the other fellas gave him a hand transferring this new motor over to the cockpit of his sailboat, where he heaved it up on the railing of the pushpit. I was watching this whole process and thinking about how fragile the railing looked with this monstrous four-stroke behemoth hanging on it.

Well, to get the point, a few minutes later the fella was headed back toward the parking lot with the old motor on the fancy carrying cart, the one being replaced by this new Honda 2005 four-stroke that probably cost $4,000. It was a 1964 Johnson Sea Horse 3-HP.

I stopped the fella to chat for minute as he came by my boat.

"Finally killed that ol' Johnson, eh?", I asked him.

"No," he said, "It still runs, but I thought I get me a new motor after 40 years."

Well, there you have it, another random data point about the reliability of Johnson outboards. Forty years and still running. I'd like to make bet that in the year 2044 that fancy Honda four-stroke will be in a landfill somewhere.

kingfish posted 09-08-2004 08:10 PM ET (US)     Profile for kingfish  Send Email to kingfish     
touché
jimh posted 09-08-2004 08:12 PM ET (US)     Profile for jimh  Send Email to jimh     
Just looking at the list of repairs, and thinking...

--"New Fuel Pump" --this was probably a rubber diaphragm replacement. Often gasoline laden with alcohol attacks these, or the diaphragm has a puncture in it. It is unusual to replace the whole pump assembly. Normally just the diaphragm needs replacement;

--"New Plugs and Wires"--replacing the spark plugs is a yearly task. Replacing the wires is somewhat unusual, unless they showed signs of damage and decay to the rubber insulation.

--"New Water Pump"--normally just the water pump impeller and a few gaskets need replacement. In some extreme cases the pump housing needs replacement. Often this is done on an annual basis.

--"New Starter"--this is very unusual, but perhaps the old starter was worn out and killed by excessive cranking. If the engine was in poor condition and reluctant to start, you could wear out a starter motor trying to get it running. However, typically a starter motor lasts the life of an outboard engine, which is twenty years or more.

--"A full tune-up"--there really is very little to "tune up" on most two-stroke engines. The engine spark timing and advance needs setting, but this is rather simple. The carburetor idle jet setting needs adjustment, but usually this can be done in a few moments without much fuss. I've seen LHG tweak all the carburetors on his twin straight-six Mercury outboards in a few minutes at the dock, just tuning by ear. So no big deal to tweak the carburetor idle jets. You might have to set the idle speed--again this is an annual adjustment or check on most motors.

Overall, from the laundry list given, I would say that the only thing unusual about the engine service was the replacement of the starter motor. The rest of the items are fairly typical or a carburetor two-stroke engine's normal maintenance. Yeah, yeah, some guy has a Yamaha that has run for 15 years and nothing has been done to it. So what. Most people change their spark plugs every year, throw in a new water pump impeller at least once every five years, check the idle speed, idle jets, and spark advance timing once every five years, and, if they're not lucky, get a hole in the fuel pump rubber diaphragm once every five years due to lousy alcohol-laden gasoline.

On this basis, I do not think that a seven year old Johnson outboard has shown anything especially unusual in terms of required maintenace, with the exception of the replacement of the starter motor.

jimh posted 09-09-2004 07:20 AM ET (US)     Profile for jimh  Send Email to jimh     
More thinking about the starter motor failure...

The duty cycle of a starter motor is normally about five seconds on and three hours off. If you read the owner's manual, it will probably tell you that in no case should you crank the starter motor for more than about ten seconds, followed by two minutes of rest before the next crank. That is the recommended duty cycle.

If you crank and crank and crank, the motor will get extremely hot, and, like almost everything electrical, when it gets too hot it will fail.

If a 1997 outboard needed a new starter motor, it seems reasonable to me that the failure was probably brought on by over heating of the motor caused by excessive duty cycle--too much cranking.

There does not seem to be an epidemic of Johnson outboard motors needing new starter motors after seven years, so I don't think you can reasonably put the cause of failure down as a defect in workmanship or lousy quality. The motor worked for seven years, then it failed. Probably got over heated trying to crank the engine.

Peter posted 09-09-2004 09:15 AM ET (US)     Profile for Peter  Send Email to Peter     
BigS, according to Boatfix, the Sierra replacement coil for the 48 Johnson is all of 14 bucks. Intermittent operation of a cylinder typically indicates an electrical problem. Coils are the usual suspect.
bc posted 09-09-2004 05:58 PM ET (US)     Profile for bc    
I just recently purchased a '90 model 48hp spl. I am very impressed with the quality built into these motors. Over the years I've owned a '78 25hp omc, '87 25hp merc, '84 40hp omc and a '83 70hp omc. So far I would rate this one with any of the above mentioned. On a 15' striper I'm getting 32 mph with two adults, 12 gallons, 2 batteries. 2 cyl. omc's are some of the easiest motors to work on are economical. Good luck fixing yours.

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