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Johnson 70hp issues

T

TD28

Contributing Member
Hey everyone just picked up a 20ft pontoon with a 70hp johnson on it I believe it's around an 88 model serial tags too faded to get info from. Just got a couple things with it. When I put it in reverse the throttle controller vibrates and makes a odd sound. Second is above half throttle it starts bogging and rpm goes up and down some. I did notice some milky water gas mix coming from carb.

Half throttle was good no issues so im wondering if it was getting too much air from still plugged oil injection stuff or sucking in water cause this thing throws a lot of water at the engine.

What I've done so far

Compression test all 3 cylinders have 125 psi
Fresh plugs today.

At some point the auto oiler was removed but not capped off I capped the end at the fuel connector and unplugged all wiring for the system. My thoughts here were water was maybe getting in from there and making their way to the carbs since there isnt a carb cover.

Tested good today on muffs but looking to see if anyone has any advice since my only outboard experience comes from working on a old chrysler.

Thanks in advance
 
No box was on it when I bought it. As far as I can tell no water in the tanks. Engine was not shutting off or anything.
 
The engineers jetted the carbs for proper operation with the airbox installed.

Reverse "odd sound" may be that it isn't properly adjusted & not completely engaging in reverse. In other words, reverse gear & shift clutch are destroying themselves.

VRO was disabled why? Failure or just prior owner listening to hearsay?
 
For reverse its not really doing anything at the engine but the sound and vibrations coming from the control box. I

Not sure why they disabled it but they removed everything from the engine except what I assume is some motor for it that I'll attach as a pic.

I have a parts 60hp that's all the sairborne. Missing the air box as well as a few older evinrude 60-75hp from 68 to maybe 80 I'll see if the evinrudes have a compatable airbox.
 

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The electric primer is a valve !-----It is used for cold starting the motor.-----Takes the place of choke flappers on carburetors.----Push the key in and hold it in while cranking the motor over.-----Makes for near instant starts.----Get the kit to repair the broken red lever.----Get a manual for your motor as it will save you a lot of $$ by knowing how to operate this motor.-----The red lever is for manual operation of the valve should you need to start the motor with a dead battery.----The electric primer valve has nothing to do with oiling.----These 70 HP motors are wonderful , but easily destroyed by a novice guessing on things.----Sorry to be blunt here.
 
All good id rather have bluntness honestly. I checked at my in-laws and found the silencer. Ill change it that valve with the one from the spare engine since its not broken. Thanks for that info
 
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I've adjusted the cable to max at the engine and it seems to still need just a little more. Is there a way to adjust it at the controls? With cable disconnected I can manually shift it and it clicks right into gear.
 
There is no adjustment at the box.
However at this point in time and considering how many DIYers have been involved there is no saying if it's been apart & assembled wrong/parts missing.

More likely to me that the lower shift rod height has been mal-adjusted/tampered with during a prior lower unit removal. If this rod is mal-adjusted, the geometry of the linkage will be wrong not allowing proper shift spool travel.

Racer beat me to it....
 
Thanks for the advice. Ill look for a guide online and report back. I take it it'll be a lower unit drop to verify and then align
 
Dropped and adjusted. It'll go into reverse now I feel i might be a tad bit off still. I did notice quite a good bit of fuel coming from my carbs though.
 

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No idea how its getting like that. Took it out yesterday and she wouldn't go over 10mph. Gonna recheck the compression and tear into the carbs.
 
Btw are there any other ways to identify the year and model/serial? The tag is basically nonexistent.
 
Compression was 120-125 across all 3 cylinders. Carbs looked great inside no clogs or buildup of any kind. Floats also set good and the needles were clean and free moving.
 
All I see for you deterimining there is no water in the fuel is the following......
"As far as I can tell no water in the tanks."

Did you truely check or replace the fuel?
If there was water in the tank, it's been pumped via the fuel bulb into the carbs. And the fuel line may be full of a wster cocktail too.

Remove the airbox if you did install it & remove the drain screw at the front of each carb. Pump the bulb until you get clean fuel, not the cloudy stuff as shown in the picture.

It may take several pumps. Perhaps a quart total assuming the fuel in the tank is clean.
 
If any water got inside of this motor in the last few weeks it could spell death to the bearings.----Get this motor running ASAP !!
 
Messed with it some more this morning. I took samples from the tank and the carbs and had no water in the fuel. I also hooked the water up and removed plugs to see if anyone water would show up and nothing. I scoped the cylinders and the top looks normal the middle some clean spots and the bottom cylinder is almost completely clean. Now the extremely confusing part was i ran the engine on the hose until milky fuel came out of the carbs but when I drained the bowls there was no water in the carbs themselves.
Could this be a head gasket or the exhaust plate cover on the side?

Pics are the pistons in order 1 2 3.

since it also has a splined drive shaft I think its around an 89 or so correct me if im wrong
 

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Fuel/water only gets in carb though fuel line. . Without some catastrophic event .
Myself I would pump all the fuel out , pump the last gallon into a semi clear plastic jub , let sit overnight or a day and see what's on the bottom.
The bottom piston looks suspect too me . As in washed clean by water . Could be that its typical on the bottom cylinder .
There are others who would know , better then myself .
 
That's what I was thinking on the bottom. I have drained fuel out and have my second take hooked up. I did disassemble and redo the carbs gonna hopefully test it out on the water this weekend and see what it does considering I cant replicate water mix on the muffs.
 
Just ran it on the lake and it did very well was able to go 21mph. It doesn't like idle speed too much but Im able to use the high idle lever. Honda continue adjusting the shift linkage to get reverse back but im starting to think it might have an issue in the foot.
 
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