1982 Johnson 7.5hp Backfires but No Start (Wrong Carb?)

[Bjandthekatz]

Hello, I have been rebuilding a 1982 Johnson 7.5hp (sailmaster). I purchased it with no spark, diagnosed it and replaced the powerpack that now sparks and jumps a 1/2" gap. It is not starting and after 5 or so pulls it will backfire once. Looking through the parts manual the carb linkage on my outboard does not appear to match up. I believe the starting to be a timing issue (link and sync). The seloc manual was not much help with it.

I have attached a few pictures. Even after disconnecting the tiller handle and turning the bracket to the full throttle position, the cam roller does not allow the butterfly valve to open all the way inside the carb. Will this carb/linkage situation allow the boat to start? I attempted to hold the butterfly valve open, push the disconnected linkage to the maximum spot to advance spark and crank to imitate a full throttle crank, and it would still not run.

Any other advice or recommendations? Thanks

 

[Crosbyman]

tried inverting (reverse) the plug wires ????

 

[racerone]

That does not look like a 1982 model 7.5 HP carburetor.----Model # of your motor ?

 

[Bjandthekatz]

tried inverting (reverse) the plug wires ????

Wow, I can't thank you enough. Just went by the manual and assumed the it was correct. Switched the leads and she fired right up. Ran for 2 minutes and then stalled out and wont restart. Time to get to diagnosing that

 

[Bjandthekatz]

That does not look like a 1982 model 7.5 HP carburetor.----Model # of your motor ?

The imprint on the freeze plug says E8RLCNR (E0031529)

 

[saltchuckmatt]

I agree with Crosby, coils are probably wired backwards, switch plug wires and test.

 

[racerone]

Looks like a carburetor off a 6 hp to me.----A 1979 or older 6 hp motor.----Recoil rope is too short as well.

 

[Bjandthekatz]

Looks like a carburetor off a 6 hp to me.----A 1979 or older 6 hp motor.----Recoil rope is too short as well.

I had to cut the recoil rope when I took the powerhead off. I'll get a new rope on there. Is the length mainly just to make starting it easier?

As for the carb, should I bite the bullet and buy a used OMC carb from eBay? I only see one of them on there and its $150. If not, I'm guessing it will run too lean in the higher RPM range?

Really appreciate the help

 

[saltchuckmatt]

What's wrong with your carb?

Post a picture of your motor from farther back.

 

[Crosbyman]

now that the plug wires are in the proper place ....just clean the carb... check the fuel pump filter if any before it dies try pumping fuel up the carb with the hose pump if it stays running thefuel pump is in need of a close look.

see an old carb... much like yours except for the lower needle being a orifice behind the lower 7/16 bolt at the bottom of your carb

part is yellow is the low speed circuit of these old carbs

see link fyi

Leeroy's Ramblngs is coming soon

We are doing some maintenance on our site. Please come back later.

www.leeroysramblings.com

 

[Crosbyman]

I agree with Crosby, coils are probably wired backwards, switch plug wires and test.

he switched them ...

 

[saltchuckmatt]

he switched them ...

I know, as I was writing he posted the success.

 

[Bjandthekatz]

What's wrong with your carb?

Post a picture of your motor from farther back.

Here are more pictures

Edit: and for the carb, the linkage does not look like what I have seen on parts diagrams for my engine.

 

[Bjandthekatz]

now that the plug wires are in the proper place ....just clean the carb... check the fuel pump filter if any before it dies try pumping fuel up the carb with the hose pump if it stays running thefuel pump is in need of a close look.

see an old carb... much like yours except for the lower needle being a orifice behind the lower 7/16 bolt at the bottom of your carb

part is yellow is the low speed circuit of these old carbs

see link fyi

Leeroy's Ramblngs is coming soon

We are doing some maintenance on our site. Please come back later.

www.leeroysramblings.com

I rebuilt the carb prior to swapping the spark plug wires with an OMC rebuild kit. It did not have the low speed pack nut in the rebuild kit so I'll see if I can find that online. The issue I was wondering if perhaps the timing advance was incorrect because the carb and linkage do not look like anything from the parts diagram I've seen online.

 

[Crosbyman]

odd your top coil is wired to the bottom plug and vice versa

maybe it is normal.... or the control leads from the magneto to the coils are reversed...

 

[saltchuckmatt]

Yes I agree, wires from mag need to be switched going to your coils. Should be orange blue to top perhaps.

Does your motor have the airbox? And where is the choke knob?

Motor still isn't running?

 

[racerone]

This motor gas a 6 HP carburetor from a 79 or older model installed.-----That is why it looks different from what is shown in the parts book for an 82 model 7.5 HP----Simple.

 

[Crosbyman]

Yes I agree, wires from mag need to be switched going to your coils. Should be orange blue to top perhaps.

Does your motor have the airbox? And where is the choke knob?

Motor still isn't running?

after you switch the wires to the coils from the magneto put the top coil HV lead to the top plug.. bottom to bottom

 

[Diplomasta]

Have you inspected the reed valves??

 

[oldboat1]

The typical cause of a backfire is the idle air/fuel adjustment. The initial setting should be around 1 1/2 turns open (counter clockwise). This assumes that the needle is intact, along with the assembly. Additionally, the flywheel should be removed so you can check the flywheel key. If the flywheel was not torqued to specs, the key may have sheared causing a timing issue.