1972 Johnson 125 horse outboard issues

[Mfribley]

I recently aquired a 16ft 1977 Sea Sprite with a 1972 Johnson 125 horse outboard on it on a trade for a vintage 5th wheel my wife and I never used the. I know that the 125 is far too much horsepower for the boat which should be 80 horse max so I will never run it at full capacity as I know too large of an engine could bust the transom right off and ideally would love to trade down for someone who wants more horsepower!

It is an old motor and not without it's issues upon my initial inspection in the driveway everything looked to be in decent shape new plugs and wires as well as some upgrades on the wiring dual batteries and selector switch he had the carbs cleaned. But he told me it was "cold blooded" and had always been a bit of a pain to start but once it warmed up it ran great he told me the trick to getting it going which works good however once it gets going. The throttle works intermittently there are times where it will get up and go and other times it will big out and stall I went today to check the points and found that all 4 plugs were loose I torqued them down cleaned the fuel filter out and inspected the engine a bit closer and found a few other simple things anyways I am hoping this will help quite a bit... But wondering of loose plugs could cause the engine to bog down and stall when accelerating what else should I check before taking it out on the water

I appologize if I sound dumb I am familiar with smal engines and cars but not outboards this is my first boat and would love to get this engine running smooth so I can out it up for trade for a more adequate size for the boat

Mike

 

[jimmbo]

Welcome to iboats
The 125 should have a pointless ignition system. As for loose spark plugs, that will kill the compression, reduce power and probably cause some erratic operation(40 yrs ago the old man stripped a spark plug thread on our V4 90, the looser plug really killed the power . Your engine has fixed low speed jets so no mixture adjustment there. When the previous owner had the carbs cleaned, I hope there was a linkage sync done to keep the carbs synced together as well as with the spark advance. Have you ran it since you tightened the plugs?
Myself I wouldn't worry about the 125 wrecking the transom. A V4 85 hp would put more strain on the transom as it has better low end torque than the 125, weight is pretty much the same too.

 

[oldboat1]

Choke plates have to close tightly for cold starting (might choke manually). Jimmbo makes an interesting point. If the hull is rated for 80hp, though, that's another issue -- lot's of discussion back and forth on that in prior threads.

Think I would want to be sure the transom is sound in any case. You can replace the plywood core yourself, without an awful lot of trouble. Lot's of threads on that too.

 

[Mfribley]

Thank you both for the info when I lift the toggle switch for the electric choke the plates do slam shut and will open up once I let off the switch I am contemplating putting the manual choke back on as there is a spot for it and opting not to use the electric choke I have a few more things I need to do before I take it out tomorrow the spring hose clips are worn out on the fuel lines as I noticed some gas in the water they are extremely loose my assumption is it is not only leaking fuel but allowing air into the gas lines and not allowing enough fuel so I picked up some hose clamps from the autoparts store tonight. I will have to see if I can find the specs as far as the engine rating for the transom all I know is it is a 16 ft fiberglass tri hull Sea Sprite but haven't been successful finding specs online I will however update you on how it runs with the tightened plugs and fuel lines. Tomorrow

 

[racerone]

Replace the o-rings in the fuel connecter !

 

[Mfribley]

Alright I finally has a chance to get it in the water and not much luck this is getting frustrating it would turn over and fire for about 30 seconds die out and not want to start again I ended up manually choking the engine but stupid me I left the battery on and it was pretty weak and eventually died I noticed I am still leaking fuel the primer bulb will pump up and lose pressure within a minute or so (it's my understanding that once primed it should stay hard for some time) I replaced the O rings in the connector planning on just going and buying a new one today, and I have to check the gasket on the filter/pump for leaks which is where I believe it to be leaking at as well

However I started thinking as I was pulling it out of the water to check the plugs I pulled two and they were fouled I assumed that the excess oil in cylinders from the boat being run with the plugs being loose when I got the boat would burn off but now I am thinking that it is causing the almost instant fouling on the plugs so my next question is HOW DO I GET THAT CRAP OUT I have read to pull the plugs disconnect the fuel line and crank the engine over several times while covering the plug holes with a rag and that the engine compression will blow the majority of the oil out
Will this work

 

[oldboat1]

Sounds like you might be better off selling the current motor as-is, and getting one you prefer -- put your time and money into the replacement motor.

Whether that 125 or a replacement, plan on the full monty -- compression and spark tests with the right testers, clean fuel, oem plugs, new impeller.... Maybe rebuild fuel pump and revisit carbs. All basic stuff but takes some time and money even if no serious issues.

If trying to get the current motor up and running, start with basic tests (and fix the leaks.) Fresh fuel (check for water in tank). 50:1 ratio. If you have unburned fuel in the cylinders, I would get an open air spark tester as a first priority, and do a compression check so you have a baseline. If you run it at all, should replace the impeller or you risk busting up an old one and clogging cooling passages.

Not trying to be negative -- just done it many times. All fun, but can be frustrating.

 

[F_R]

That ignition system on that motor was state of the art in 1972. But in hindsite, it really wasn't all that great. The distributor was a pos. The original spark plugs were L76V, but a lot of people find that QL77JC4 work better, especially with marginal ignition performance.

 

[jimmbo]

POS, impossible?:frusty: In the brochure it sounds like it was perfection

http://www.boatinfo.no/lib/johnson/brochures/1972johnson.html#/18

 

[Mfribley]

Thank you for the advice I am considering letting it to as is!!!!!

The plugs in it were NKG plugs and were not compatible with the QL77JC4 when I did a cross reference on the numbers and "spare" set in the glove box was way off I wish I could say I was surprised but at this point I am not.....so it was off to the hardware store they had the champion ql77jc4's I will be running a compression test within the next couple days

After working on the fuel lines the only leak I can find anymore is when I prime the bulb it leaks out the pinhole in the back of the fuel pump if I over prime found fuel pumps online cheap enough going to check the local boat store as well and see if they have one in stock I wanted a project boat as I enjoy working on things but this seems like I bit off more than I wanted

 

[V153]

Well it certainly sounds like you've found yourself a project. (Do people no longer check if something runs before they buy it?)

Regardless. I'm relatively sure fuel shouldn't leak from the pump when ya squeeze the primer ball.

 

[oldboat1]

You should be able to get a kit for that pump (0438559), and that would save some money. Chances are, the diaphragm just needs to be replaced.

I would do a compression check and see if you want to continue work on it. A local auto store might loan out a tester. While there, buy a $10 open air spark tester (adjustable). You need to check the ignition system to see if it's producing spark, then move to replacing plugs. Remove plugs to check both compression and spark, and use a fully charged battery. (If in doubt about the battery, get it tested.) To check compression, crank it on each cylinder until the needle stops rising, and note the reading. Look for a balance between cylinders.

If you measure good compression and spark, it has a chance -- but have to get some numbers. I think the spark should be around 3/8" on your '72, maybe a little more (and "snappy"). Get a good ground with the spark tester.

 

[V153]

That ignition system on that motor was state of the art in 1972. But in hindsite, it really wasn't all that great. The distributor was a pos. The original spark plugs were L76V, but a lot of people find that QL77JC4 work better, especially with marginal ignition performance.

It really was state of the art back then. Only one coil and a big 'pulse' pack. Didn't the plug wires come off the timer base?

 

[F_R]

It really was state of the art back then. Only one coil and a big 'pulse' pack. Didn't the plug wires come off the timer base?

No, it had a single coil, leading to a distributor cap & rotor under the flywheel. The distributor cap & rotor then directs the spark to the proper plug wire (hopefully).

 

[Mfribley]

Thanks for the advice I pulled the plugs one by one yesterday and had my wife crank it over while I held a rag over the cylinder to get the excess oil out it seemed to have pretty solid compression I am renting a compression tester after work and buying a open air plug tester to check the spark also completely drained the gas out of the tank and put fresh 50:1 outboard mix into the tank( I found a bottle of cheap ATV air cooled two cycle oil when I pulled the tank to drain it) so we will see how it goes all of your advice is appreciated I am already looking for an affordable 60-85 horsepower motor I found the rating on the boat it's rated for 85 horse max

Mike

 

[oldboat1]

Only issue that comes to mind is use of oil for 2-cycle air cooled engines. Probably better than using marine oil for air cooled motors, but still better to find some TCW-3 rated marine oil for your motor (doesn't have to me BRP branded).

(In looking at replacement motors, I would consider '70-'80s Chryslers (or Force) as well, 55 to 85hp range. I've run three or four Chryslers and like them -- may be able to find one at a bargain price too. Check compression and spark before buying, if you can -- good idea with any motor.)

 

[jimmbo]

( I found a bottle of cheap ATV air cooled two cycle oil when I pulled the tank to drain it)

Evidence the previous owner didn't treat the engine well. Once you get it running, it might be a good idea to run a few cans of Engine tuner through to ensure the rings aren't carboned up/sticking from the wrong oil

 

[Mfribley]

Well my father in law checked the compression it was good spark was good I picked up the proper plugs at the hardware store and put those in we went down to the boat launch not only did it fire right up it ran way better I will put some engine tune through it as well...

I ordered a new impeller and planning on taking it to my dad's next weekend and installing that but overall it is running great

It's amazing how much of a difference fixing and tightening all the fuel connections and having the plugs specific for that engine can make clearly the guy I got it from had no idea what he was doing however at least the engine wasn't toast and was saveable

Thank you all for your advice and input

Mike

 

[oldboat1]

Well done! :thumb:

 

[V153]

Way to go! Post a pic?

Fwiw horsepower is like money in the bank. Don't have to use it all at once. I run a 140 on a boat that's rated for 80 with no problems.