Help Needed with 1985 Johnson 70HP

[jimmy spy.]

Hello! First time posting here, so I apologize if this is in the wrong section. I also apologize for the wordy first post.


I've got a 1985 Johnson 70HP VRO outboard that I recently transplanted onto a 1965 Starcraft Del-Ray. Up until a month or so ago, the motor had been sitting for close to 10 years. Because of this, I took it to a mechanic to have the carbs rebuilt and have the water pump replaced ( I generally would attempt a repair like this myself, but I got a good deal on the boat and didn't really want to mess with the carbs). Well, I got a call from the mechanic saying that they couldn't get the motor to run right, and they were sure it wasn't a carb issue. I did't want to pay their hourly rate to have them look into the issue farther, so I picked the boat up this past weekend and plan to fix it my self.

So, here is what the motor is doing. It starts up and idles fine (although the idle is set way too high), and will go into gear, but it bogs down and dies when you try to give it anymore than 1/4 throttle or so. After playing with it for awhile, I could get the motor to open up by dropping it in gear and immediately going to WOT (this only seems to work some of the time). Once you get the motor to open up, it runs beautifully. You can adjust the throttle freely without it bogging down or stalling until you get back down to 1/3 to 1/4 throttle or so, then you have to play the "floor it and hope it doesn't stall" game again. When backing the motor down from WOT, it doesn't bog down or stall out at any point in the rpm range; issue only seems to occur under acceleration. Issue also seems to be independent of motor temp (does it from a cold start and at operating temp).

The motor has good compression and spark seems to be fine. As mentioned, all 3 carbs have been rebuilt. The motor does have the VRO fuel pump still, but the oil injection line is blocked off.

So, any ideas on what could be causing this issue?

 

[flyingscott]

Have you tried pumping the fuel ball when this happens? Have you checked for spark? Have you looked to see if the timer base is sticking?

 

[cesandroid]

What do the plugs look like?

 

[jimmy spy.]

Flyingscott- I didn’t try squeezing the primer bulb (was out by myself and couldn’t reach the primer and the controls). I’ll have to try that and see if it makes a difference. Spark is good (I checked it by holding the plugs near the block and cranking the motor over. Mechanic confirmed). Do you have anymore info on this timer base (what/where it is and how to check it)?

cesandroid- plugs looked fine. A little yellowing but no excessive carbon build up (granted they have very little run time on them).

 

[dabrackmaster]

If using the original VRO pump and bypassing it, try removing it, the two diaphragms inside tend to dry rot. BEWAREZ it's a little irritating putting it back together, and d ont overtighten those screws. It will warp the housing and make things worse.

Also use a short piece of NEW hose plugged on one end for the OIL-IN port of the pump.

That and a glass inline filter coming apart was killing my midrange and idle

 

[jimmbo]

You are going to have to go inside the carbs and see if the floats are set right, that the needle and seat are clean, that all the fuel passages are open. that means removing the welsh plugs on the carb to get to the areas where the idle circuits feed the carb throat. Fuel pump diaphragm is suspect too. As mentioned the timer base may be sticking. Proper sync between the carb and timing advance, as well as max advance.
Myself, I prefer to premix my fuel, so as to remove any worry about the VRO/MRO pump working.

 

[flyingscott]

The timerbase is under the flywheel and moves with the throttle. Make sure it moves freely.

 

[jakedaawg]

This sounds like a link and synch issue to me...I didn't read everything...

assuming compression was also verified...

 

[jimmy spy.]

Thanks for the responses everybody! I spoke with the mechanic that actually did the work on the motor today (he wasn't there when I picked it up and was off yesterday). He said that squeezing the primer bulb didn't help any, but pushing the key in did seem to help (he referred to pushing the key in as "priming", but I was under the impression this was a choke). He said his best guess was that it was starving for fuel, and it might be a fuel pump issue or a leak in one of the crank seals.

Is there anyway to test the VRO fuel pump? If the fuel pump is going bad, I'm wondering why squeezing the primer bulb didn't help.

jimmbo - All of the carbs were rebuilt (with carb kits). The mechanic said that they went through them all a second time after they lake tested the motor and discovered the acceleration issue. Not saying I'm ruling out a carb issue completely at this point, but I'd really rather not open them up if I don't need to haha

flyingscott - Do I need to pull the flywheel to inspect the timer base, or will I be able to detect any issues by moving the linkage by hand?

jakedaawg - I did do a compression check on the motor before I took it to the mechanic (they did one as well). All three cylinders were within 8-10 psi. I've heard/read the term "link and sync" thrown around a lot with these motors. What does this entail? Is there a procedure out there for it?

 

[cesandroid]

Are you sure the motor is hitting on all 3 cylinders?

 

[jakedaawg]

The "link and synch" is a step by step process that sets the carbs throttle linkage and idle mixture to the advance of the timing. When motors dont advance before the carbs throttle plates open they tend to fall on their face and bog or die. A factory manual outlines the process. No one is going to type it in as its 28 or so seprate steps...

has this motor ever run well for you personally?

was the mechanic you took it to an actual boat guy with a shop and all? These motors are pretty simple for any pro with any J/E motor experience...

 

[jimmy spy.]

cesandroid - I'm pretty sure it is, at least some of the time. At WOT (when I could get it to open up) the boat was running ~35mph, which is what I would expect for this setup. I don't know if it is always running on all three though.

jakedaawg - ohhhhh, ok. Sounds like I need to get my hands on a service manual. I assume everybody is going to recommend a factory manual over an aftermarket one?
Last time I saw it run, I was pretty young, so yes and no. haha This motor was on my grandfathers boat. The boat had a soft floor and we junked it after he passed, but pulled the motor off. It's been sitting in the garage for 10 years or so, and wasn't used the last few years my grandfather had it.
The marina that worked on it is an Evinrude dealer. They were pretty highly recommended, although I wasn't incredibly impressed with their service manager. They were hesitant to put any more work into a "motor this old", and I was already paying more than I wanted to for a carb rebuild and water pump, so I just paid for the work done and picked it up.

 

[cesandroid]

As its idling, pull 1 plug wire and plug back in at a time and listen. You'll know if its missing.

 

[jimmy spy.]

cesandroid - Ok, I will give that a try the next time I have it running.

Also, I picked up a factory service manual today (should be here sometime next week), so I'm going to go ahead and try the "link and sync". I'll report back with my findings.

Thanks again for all the ideas and suggestions!

 

[flyingscott]

If pushing the key helped the problem you have a carb issue.

 

[Joe Reeves]

Pushing the key in engages the Fuel Primer Solenoid that replaces the choke butterfly scenario.It causes the fuel to bypass the carburetor and flow directly into the intake manifold. An improvement in a engines performance when engaging that solenoid indicates a carburetor problem.

The high speed jets are located horizontally in the bottom center portion of the float chambers. Clean them carefully with a piece of single strand steel wire as solvent just doesn't do that job properly. Fuel must flow freely through that jet before it can flow to any other fuel passageway.

The small jets at the top front portion of the carburetor are "Idle Air-bleed Jets" that control the air/fuel flow mixture... keep in mind that they measure "air"... NOT fuel! Enlarging the center I.D. of those jets cause the engine to run leaner... it Does Not result in a richer mixture as in the older models of yesteryear! This pertains to your 1985 70hp model.

If that engine has adjustable needle valves in place of the air bleed jets... it has the wrong carburetors installed. Let us know which you have on that engine.

A word of advice... When a mechanic uses wording such as "I think"... or my "Best Guess", he is thinking, not knowing, and guessing with your money! Think about that!

Basic troubleshooting.... All spark plugs removed!... What are the actual compression psi readings of each individual cylinder?... Spark must be checked by using a tester whereas a air gap of 7/16" can be used. The spark should be a strong blue lightning like flame... a real SNAP!... Is it?

****************
(Link & Sync)
Throttle cam roller backed away from the cam... Adjust the linkages between the carburetors so that the throttle butterflies open and close at the same time... you do not want a butterfly or two closed and one ever so slightly open.

Adjust the throttle roller so that the throttle butterflies just start to open when the scribe mark of the metal cam aligns dead center with that roller... Not before or after.

The roller should be approximately 3/8" in diameter... if it is more like 1/8", the outer covering has broken away, in which case, replace it as that smaller size throws everything out of whack to a point that nothing can be adjusted properly.

Check the idle timing degree as per your manual... The timing should read properly when the scribe mark of the cam is at that dead center alignment with the throttle roller. If it is not, then the adjustment (distance) between the vertical throttle arm of the engine and the metal cam is wrong... correct it. (That's it)
****************
Get back to us with the compression and spark info etc as above.......

 

[jimmy spy.]

You guys are scaring me with this "carb issue" talk! haha

So I had a chance to mess around with the boat a little this past weekend. I confirmed that the motor is running on all 3 cylinders. I also confirmed the mechanics observation about pushing the key in. If you push the key in briefly just as the motor begins to bog down under acceleration, it "cures" the issue (or at least the symptoms).

My shop manual arrived a few weeks ago, and I have started perusing the "link and sync" section. I think my plan is to walk through this first, and then move to rebuilding the carbs again if the issue doesn't go away.

The boat goes into winter storage in a couple weeks, so a lot of this may have to wait until spring.