Logo
FULL SITE MENU

Johnson 50 hp 4 stroke issues

B

barramundi

New member
First of all great forums! Hopefully I can find some help here and return the favour sometime!

Ok I have had a 50 2 stroke for 5 years, old and was time to retire it. didnt have much cash to spend so i picked up a Johnson 50hp 4 stroke 2004 model. Before I purchased the seller offered me a boat drive to see the motor perform.
Motor started first kick like a dream. sounded great. Went for a 15 minute run and it hooted along just fine at 6500 rpm.
So i purchased the motor.

A week later I take delivery and bolt it on to my boat and take it for a test run. I get about 500 meters up the river and as I go over 4000 rpm the temp light comes on and the boat start limping till i back off the throttle. Weird it didn't do that on the other guys boat....
I checked the engine by hand and it felt normal not too hot and the water from the tell tail felt normal as well. Mind you it was serviced just before buying and has new cooling system, tell tale is strong from the motor.
So im thinking it didn't actually overheat?
I let it sit for half hour then tried again. I could drive at 4000 rpm for as long as I want, step over that mark and on goes the light again???

So my first question is what could be happening here? I installed the motor, was pretty easy till I got to the wiring so I'm wondering if I have done something wrong... At the engine end of the wiring it was straight forward, all plugs that had their own sizes and shapes so you couldn't get that wrong. But at the dash end is where i struggled.

I hooked up the wires to the tacho, it lit up and worked and that's also where the warning light is so I'm guessing I got that right. There was a trim tilt gauge but I didn't bother installing that and left the wires unconnected. There was 2 plugs that plugged into the control box and that was straight forward too. All that was left is a square plastic 2 pin female plug I believe is the alarm wires, I also didn't hook this up as I couldn't find the male plug it joins too..... Is it a problem that i didn't hook up the trim tilt gauge and alarm wire?

So that's my first issue...what could the alarm be going off for and should i hook those wires up or no big deal?

2nd issue is when my boats in the water I can not hear any noise from the gearbox but when its in the driveway with the hose hooked up to it i hear some slight noise from the gear box when its in gear. Should there always be no noise at all or do some motors make a bit? or am i just paranoid? The prop has a bit of a wobble to it, I think its a bit warped and going to replace it. I cant see any shaft wobble at least not with my eyes. I dropped the oil after a run and it was like new, no water intrusion and no oil has leaked out either.

3rd and final issue is when its under way it sounds awesome and so smooth! but when its at idle it vibrates the boat and makes everything rattle in the boat. is this the nature of the beast or should it not vibrate and I have another issue to deal with?

So stressed over this new motor and just don't have the $$$ to pay someone to fix it....they charge like a wounded bull in my town! A mate just paid $800 to get his carbies tuned lol
Hoping the pros can help me out here!

Thanks in advance guys!
Rob
 
First of all, I'm not a Pro, just a long (39 yr) time boat owner (SB, IO & OB), maintainer and 'fixer'. I got 'soured' on Pro maintenance long ago when arriving early to see 'copper' paint going on with "No Copper Paint" plainly written on the Work Order.

If you've not already done it, be sure to get a Service Manual for your engine. Your wire hookup was probably correct, Engine Owner's Manuals (available as free download from manufacturers) usually have wiring diagrams but SM's go into much greater detail. They would be in your local Library and you could check there to see if you prefer Clymer's, Seloc's or Factory SM. In my case, Factory SM is all I need for Honda and Factory SM + Clymer's is needed for Yamaha (IDK about Johnson). Don't forget to check local 'used bookstore' (or eBay), that's where all my no-longer-owned SM's went. I'm looking ahead for a future re-power and want to consider Evinrude, which is what brings me here.

On OH warning: There could be many reasons it didn't lite off on demo and does now but important thing is, don't ignore (or disable) based on what you see/feel from tell-tale' or outer temperature felt. With all that Lake/Ocean water to pump from, it's common for a dangerously hot area to not be found/felt, but trust that warning. Need SM (or 'Pro' here) for detail, but should be easy to find and temporarily remove your OH Sensor and test it with your OHM Meter and a Candy Thermometer in a pan of water on your stove, they rarely fail so do this before buying one.

Temporary high heat condition could come from other than Cooling System issues, like an over-lean fuel condition in one or more cylinders or incorrect ignition timing. Besides Water Pump (assure Pump Impeller was replaced if possible), there could exist a partial blockage in a portion of your internal cooling passages that would only cause overheat under higher power conditions. Thermostat and pressure control valves should be easily accessible for you to clean and test.

I don't recall hearing gear box noise on muffs, but we not only don't put in gear on muffs, it's recommended to first remove your prop. Actually this is not such a bad idea considering how expensive a little fishing line wrap in there could get. You should have an upper plug (get some extra '0' rings or washers to have) to check your gear oil level, any 'milky' appearance in that oil indicates water entry. (After typing that, I see you did check your gear oil :))

Before replacing your propeller, take it to a local (usually away from expensive waterfront locations) Prop Shop as they can work miracles in fixing blade damage as well as changing your 'pitch' (they can usually go at least an inch up or down) so you can match your boat (for better 'hole-shots' and efficient cruising RPM). It's unlikely that your Hull would offer same 'resistance' as the seller's hull. And of course, proper balance would be most important for long life and smooth operation.

A Four-Cycle engine should idle smoothly (unlike most Two-Cycle) the first (easy) thing to check would be Carburetors adjustments (idle screws, balance, etc.). Next would be ignition timing, there should be adjustments for low speed as well as high speed, your SM will probably start you out confirming that #1 piston TDC matches mark at flywheel... Valve tappet clearance settings (a regular maintenance item) are important for smooth (and trouble free) operation as well, larger engines use Hydraulic Lifters which adjust automatically with healthy engine oil. A Compression Testing tool ($23 at Harbor Freight) is a "Must Have" for you (have it on muffs or in a bucket when you spin it to avoid WP melt damage).

Becoming involved in your engine maintenance (especially for Four-Cycle) will not only save you a lot of money, it will increase your safety and confidence on the water, where engine 'stoppage' is a more serious problem than in your car. This will help give you the knowledge you need to better spot engine problems before they end in stoppages. You will gain pride and satisfaction knowing 'you took care of it'.:cool:
Art
 
Thanks Art
So far I have taken a look at 2 sensors, they look clean as new no corrosion etc. The thermostat opens in 11 seconds in boiling water. So i guess the 2 easy fixes aren't the problem :(
 
Now you need your Service Manual.

Thermostat test is not that it opens in Boiling Water (although it certainly should), but (using a Thermometer) exactly what temperature does it open? Your SM will give a specific temperature as well as a minimum 'rise' of the valve to measure.

Likewise on your Sensors, using an OHM Meter and suspended in heating water, you note the temperature at which your OHM Meter tells you its contacts have closed (will be well below boiling) and then as water cools, what temperature does the contact open again.

If I had to guess, it might be something like minimum of 125f for thermostat to start to open and 3/16" minimum rise (of valve) by 130f and the sensor to make electric continuity contact at 185f and then open again as it cools down through 150f. Each engine model will have its own specifications.

If you have to buy one, a candy thermometer works well and is least expensive, (look in a 'Dollar' Store) but if you have a meat thermometer, it will do the job. You can calibrate your thermometer in boiling water which should indicate 212f (100c) at sea level.

Atmospheric pressure is reduced as elevation is increased, causing boil at reduced temperature at higher elevations, so if you're in Denver, it's 203f (a reduction of about 2f {1c} each 1,000 above SL).
http://www.csgnetwork.com/h2oboilcalc.html

(Use care in opening your hot coffee thermos in an airplane :)
Or opening a radiator cap on a hot car.
 
Last edited:
Ok it ended up at the shop :( So I'm told it was certainly overheating.... Mechanic found that the Anodes had not been changed in many years and were crumbling off big chunks into the cooling system. Some chunks had gotten stuck in the valve under the power head...jamming it wide open. So unfortunately on my model that valve is a big job to get too. Mechanic has cleared all the anode out of the valve and flushed the motor to try free anything else in the system. new anodes installed. He is also replacing the water pump and soon will reassemble to retest. He says he hopes that was the problem and I hope it is too because I cant afford any more investigating!!!
I managed to find the sellers mechanic that looked after the motor before i bought it and he informed me that the previous owner had trouble for months with over heating and couldn't find the issue....so he sold it....to me :( He told me he had never had a problem with it and even when it over heated i sent him a message and he said it was strange as it had never happened before....lieing snake ripped me off....
I would love to know how he prevented the temp alarm going off on the test drive!
Thanks for your help guys! will keep you informed
 
Was the boat it came off similar in size and weight? You need to take that in account when buying a new prop. Do a WOT rpm test with that prop and adjust as necessary!
 
It came off a smaller boat, couldn't run rpm test to choose appropriate prop because i couldn't get it over 4000 rpm. When motor is reassembled and fix shop will run a test and tell me what prop i need. they said on their first test they were only getting just over 5000 rpm so i need a smaller prop. motor is a tad small for my boat but its all i got for now. Should be reaching over 6000 rpm
 
I picked up one of those " Johnsukis " a few years ago for $100.----------Had gotton so hot that even plastic bits on timing chain tensioner melted.------You have to wonder why no alarms were heard , or operator ignored them.------Just a box full of parts now.
 
barramundi said:
Ok it ended up at the shop :( So I'm told it was certainly overheating.... Mechanic found that the Anodes had not been changed in many years and were crumbling off big chunks into the cooling system. Some chunks had gotten stuck in the valve under the power head...jamming it wide open. So unfortunately on my model that valve is a big job to get too. Mechanic has cleared all the anode out of the valve and flushed the motor to try free anything else in the system. new anodes installed. He is also replacing the water pump and soon will reassemble to retest. He says he hopes that was the problem and I hope it is too because I cant afford any more investigating!!!
I managed to find the sellers mechanic that looked after the motor before i bought it and he informed me that the previous owner had trouble for months with over heating and couldn't find the issue....so he sold it....to me :( He told me he had never had a problem with it and even when it over heated i sent him a message and he said it was strange as it had never happened before....lieing snake ripped me off....
I would love to know how he prevented the temp alarm going off on the test drive!
Thanks for your help guys! will keep you informed
Click to expand...
Blockage of cooling jackets and passageways will certainly cause serious overheating problems at higher power settings. A good cleanout should solve the problem for you and "...under the power head..." gets beyond the realm of DIY. New Anodes will control corrosion and are also often beyond the reach of the owner. Waterpump impeller is a periodic replacement and if neglected until symptoms are seen, those little rubber vanes could have broken off and been pumped up into inaccessible areas to cause blockages.

Although sales between private parties are on an "as-is" basis as far as warranty goes, I would agree that this seller went (intentionally) way over-the-top in deception.

Hiding an overheat warning and engine's self-protection 'slow-down' is as simple as just disconnecting one of the leads from the sensor. You can take a little solace in that if he had not reconnected it again, you would have suffered a far more catastrophic melt-down destruction of your powerhead.

If it were me in your position; with proof of seller's deception, I would first reason with the seller to "do what is right" and should that not resolve the problem, take it into 'Small-Claims Court" for satisfaction.

All of what I know about that comes from 'Judge Judy', but you have seller's statement to you showing deception and sellers mechanic showing Proof of the Deed. Looks like a slam-dunk win and doubt seller would even show his face in court. However, unlike 'Judge Judy', there is no 'Producer' supplying funds for plaintive, so you get a 'Court Judgement' giving you ability to 'lien' against seller's assets; If he has any.

You can see how this action could easily become "more trouble than it's worth", especially if no Lien-able Assets were discovered. And now it becomes just trouble and expense 'on-principal'...

Best protection is to get *sellers mechanic* involved (if possible) prior to completing a sale. You expect to pay for a 'Pre-Buy' but it can be well worth it. :cool:

*Boat deals often depend on a "Survey" which is Professional, Detailed and Costly. But for an Outboard's "Water Trial", I would just try to do it from (or to) a location (Marina) that has a Service Technician available for you to schedule, or hire one to come with you.

Wishing you a Happy Holiday and a long future trouble-free Johnson,
Art
 
Thanks Art :)

My greatest fear now is after all the expense it still overheats....i just hope that the anode chunks were the only cause! will let you know how it goes from here
 
Nice book.
You cannot hide the alarm on these Suzuki (made for Johnson) 4 strokes by disconnecting a sensor.
The EMM will detect that the sensor is disconnected and throw a code.
This goes for BOTH temp sensors. One is a thermo switch, the other is a thermistor that varies in resistance as the block heats up. The EMM on this motor is actually smart in that it can detect a "too rapid" heat rise by the cylinder temp sensor action.

The way to disable the horn is to disconnect the horn itself. However, when (if) it overheated on the trial run, even with horn disconnected, the "Hot" light on the tach should have lit up, and the engine should have gone into safe mode, with RPMs limited to about 2500.

One other point....with the pressure relief valve stuck OPEN (as you said) the engine gets maximum cooling, not minimum.
 
Excellent information on a well designed 'fool-proof', 'fail-safe' system.:cool:

Could it have been just that demo was in an easier to drive, lighter craft that did not load that engine as hard at 4,000 RPM compared to Buyer's Heavier Boat?

I know that a 'too-long' pitched prop can really overload an engine, don't rule out a Prop Shop's ability to adjust that before buying a replacement propeller.

Fact remains on Seller's Statement refuted by His Mechanic's Statement showing deception.

It would certainly be preferable to not have had warning disabled on test run.

Lack of Pressure Relief Valve activity would result in lack of water pressure needed to circulate cooling water through All (especially upper) areas necessary and be a cause of hot spots detected. That 'Hot Spot' could very quickly burn a piston or valve at continued high power demand.

This would also result in cooler area's felt on rest of engine and cooler 'tell-tale' outlet water temperature.
Art
 
Last edited:
Well, you might overthink the function of the poppet valve (pressure relief valve), and come to the conclusion of how it works as expressed above.

However, it does not operate that way.

It is simple...as rpms rise from idle to wot, the pressure from the waterpump rises simply due to speed of pump rotation. When it hits enough pressure to lift the poppet valve off it's seat, more cooling water is allowed to flow thru the block. It is not unheard of for the temp to actually go down at WOT when the poppet opens up.

If the poppet is stuck open, the engine will run cold at idle, and normal at WOT. If the poppet is stuck closed, it will run normal at idle, and overheat at WOT.

You can actually lift the poppet off the seat by using too high hose pressure when running on muffs. When using muffs, you should strive to keep hose pressure low enough to simulate WP pressure...about 10 psi.
 
daselbee ^^^ Thank you again for explaining the Johnson Poppet Valve, I come here to learn.

That explains why that poppet valve is under the power head. (And my MINI Cooper runs 30f cooler at WOT when climbing a mountain.)

Mine is at top of cylinder head, next to thermostat and opens the same chamber as thermo, sensor is nearby, deeper in head and monitoring top of that inner chamber.
My PRV does what you say and also serves to maintain a minimum/maximum water pressure and control water flow. Removing thermostats from most engines will cause them to run cool, but often the cylinders further away from pump will then run hot due to the flow changes.

The first outboard I ever took apart was a Johnson 60 (big Pull Start that wouldn't) on Little Cayman in 1986, when there were no techs. I had never seen Reed Valves before, but I cleaned everything and it ran fine. Of course now I know; just a Carburetor clean would have done it. That was the only Johnson I've ever seen. So let me apologize for where "Johnson specific" trips up general knowledge.

As an owner, I've done all my maintenance/repair since '76. (By '86 I had a Yanmar (no repairs ever needed) and a Mercruiser (lot's of repairs) and that was before any outboard's (Yamaha & Honda now, since '96).

I come to the Johnson/Evinrude Board as I'm struggling with a very ill 24 yr old Yamaha, (also OH from blockage) expecting to have to re-power and Evinrude (3 Cylinder E-TEC 90) is the most logical choice for me. I don't want the extra weight and maintenance involved w/4-Stroke (I do love my little old Honda BF-100 which does my low speed ops) and especially don't want another "Marinized" auto engine.

So I want to pick-up Evinrude knowledge,
Art
 
Well whatever is causing the motor to overheat it happens fast....from a cold motor just entering the water it only took about 500 meters to trip the overheat alarm and only once on the plane. Tell tale always looked strong and felt normal temp. When the mechanic test drove my boat he said it was overheating. he checked for bubbles from my tell tale and he said that was good. Impeller was new. Thermostat is new, and sensors are new. Then when doing the test run he mention at one point they lost water pressure. They also had the motor hooked up to a laptop when running these tests. He said he was suspect of that valve and so stripped all the way to the valve. Apparently after speaking to the sellers mechanic he replaced that valve also only a month or two ago. So to some it up it has a new valve, impeller, thermostat and sensors and still overheated. When he looked up the inside of the leg he could see the valve and it had what looked like a rock jamming-it wide open. This later was discovered to be a chunk of anode. I don't know exactly what the mechanic managed to remove, or what was past out during operation but there was a lot of missing anode!
So the mechanic has removed the anode he could find and will put it all back together and will also wack in a new pump kit to be safe. Perhaps those chunks had caused a blockage and got caught in the valve while mechanic was test driving it? if it was a large enough chunk to lock open the valve im guessing it was large enough to cause a blockage? If I had a larger problem like a blown head gasket surely the mechanic would have picked that up in his tests? I don't know what else could be the cause of the overheating but if it goes back together and still overheats I cant afford the mechanic to invest more time on it.....
 
It overheats so fast because it's a 'spot' overheat, the builder knew exactly where to place those sensors. Blockage causing that 'spot' to not receive any water.

Salt Away is certainly a great product, best used as a preventive strategy, before a problem shows up.

I had the same OH warning after 2-10 minutes at 3800 RPM / 25 MPH Manatee Speed Limit. Chased down all the usual suspects and final pass was Salt Away.

10% solution (as recommended by OH DOT, pdf download from Salt Away web site) in a barrel. Three :45 minute runs, idle had to be slowed to 700 RPM to control the suds and water would become really hot.

Made no difference in OH warnings. Pulling Head (and Exhaust covers:eek: showed Salt Away had water Jackets clean, but there was a pile of crud buildup partially blocking water's exit behind lower edge of 3 Cylinder Head. Vinegar did not dissolve this crud either. Zinc's looked fine.

All the same, Salt Away will be included in my rinse routine for the future.
Art
 
update:
New water pump, sensors checked and fine, thermostat checked and fine, valve cleared of debris few flushes, Still over heats in 2 minutes.....
Im told it has to be a blockage in the Head??? Told it will be a big job and $$$$ :(
 
I dont see where anyone has used an IR temp gun on it. Has the actual temp been taken, and if so post it's value.
Post idle temps, temps when the OH warniing comes on....
Why isnt the engine going into SLOW mode? You have not mentioned that it is or isnt.
Is the OH temp light on at the tach?

HAve you run it WITHOUT the thermostat installed? THe hose at the thermo outlet is the outlet ofr all the cooloing water. You could pull that hose off and visually watch to see if the water flow looks restricted....a mere trickle, etc.

What did the laptop tell the mech? Was he merely reading the temps as reported back by the EMM?

I mean....is this thing really overheating or do you have a false alarm?
 
lol did you read the first post? Yes it has a warning light on the tach, and the limping home is the SLOW mode. copy from original post - as I go over 4000 rpm the temp light comes on and the boat start limping


Thermostat was new in the first place and has been tested to open correctly by myself and the mechanic.

I don't have all the temp data from the laptop but I'm told it was 90 deg at the head and 93 deg at the exhaust. And as mentioned large chunks of anode have been finding their way through my water system and this became obvious when a hug chunk jammed the valve open when they were doing the diagnostics run in the boat.

copy paste....Ok it ended up at the shop :( So I'm told it was certainly overheating.... Mechanic knows his stuff and he took the temp tools and tested as any decent mechanic would.

So if the motor overheats within 2 minutes of taking off, has new water pump, seals and impeller. new thermostat, new sensors, new valve, water is great from the tell tail,and everything else looks fine that can be seen other than the internals of the head engine etc that cant be seen with out cracking it open what else can it be? The mechanic said to me he has checked everything he can without cracking it open.
 
I stand corrected. I see now in the first post....

You have the ball. I will step back out of your way. Plead post the resolution if you find it.
 
mechanic is back from holidays...pulled the engine apart and found a very clogged water system esp in the head. once they removed all the **** they found the head had corroded right where the gasket lays around the piston circle.... So now my head is at a head reconditioning place getting welded and shaved... Hopefully they can save it as im all out of $$$ now and I cant afford a new one :(
 
OK... UPDATE...

over 2 months later, my mechanic has finally finished rebuilding my outboard. New water pump, valve, anodes, reconditioned head, all blockages cleared, sensors and thermostats checked. $3000 AUD and they take it for a test run. It over heated again! He says he got a lot further this time before it finally overheated. He was in disbelief as every part of the cooling system and engine has been either checked, replaced or reconditioned...
So Today he decided to try a cooler thermostat. Apparently it opens 15 deg cooler than the standard. He took it for a long run today and it did not overheat so he tells me. hmmmm Im happy that its not overheating but worried as to why I needed a cooler thermostat.
I do live in Darwin Aust and its bloody hot here, ocean water can be over 30 deg C. but still nobody else I know has had to replace their thermostats with cooler ones.... Got me stuffed....
Taking the boat for a run myself tomorrow to see if it overheats for me.... fingers crossed
 
I am not going to re-read thru this.

However I AM going to re-suggest that you get a digital IR thermometer to verify / see for yourself IF IT IS ACTUALLY OVERHEATING.
I know you assured me it is. What are the temps? In degrees, not "temps are good".

Take temp readings all over the head, down the plug holes, at the location of the temp sensors, etc.

Post the degrees.

You could have a false alarm, OR possibly a bad EMM, or software in the EMM that is kicking a false overheat code.
 
daselbee said:
I am not going to re-read thru this.

However I AM going to re-suggest that you get a digital IR thermometer to verify / see for yourself IF IT IS ACTUALLY OVERHEATING.
I know you assured me it is. What are the temps? In degrees, not "temps are good".

Take temp readings all over the head, down the plug holes, at the location of the temp sensors, etc.

Post the degrees.

You could have a false alarm, OR possibly a bad EMM, or software in the EMM that is kicking a false overheat code.
Click to expand...


This has been covered above. but thanks
 
Back
Top