1987 johnson 48 special idle help

[smoses99]

hello all, I am having issues with my motor i cannot figure out. I have a video but can't seem to upload, so I'll try to explain. it sounds like this motor will fluctuate to me greatly and has an intermittent backfire. 100 hr service performed on it. timing possibly? carbs not sync' d properly? any advise is appreciated, I will try to get video to upload

 

[boobie]

What's the compression on it ??

 

[smoses99]

120 on both, give or take a few, I have a crappy analog gauge haha

 

[juno pierrat]

you say backfire, that would point me to carbs not sync' d.

 

[Stumpalump]

Bad intermittent coils backfire thru exhaust. Cracked coils are a dead giveaway. The carb screews are very responsive and tune those motors nice as well if that's the problem.

 

[juno pierrat]

soooo, is backfire thru exhaust or carb?

 

[racerone]

I do not believe those carburetors have a low speed mixture needle !-----Timing is controlled by flywheel key and it may be sheared.

 

[oldboat1]

not sure what goes into 100 hr service on an '87 outboard, but sounds like you have a shop to go back to. If it ran well for the shop but doesn't do well for you, think in terms of what's different (Hint -- shop usually uses their own known-to-be-good, tank and fuel.)

 

[smoses99]

hey guys I'm back, sorry, yes backfire is coming thru exhaust, just said 100 hr service, not that it really only has 100, just saying it had a good tune up. I think I may have found an idea. feeding the carbs coming from the fuel pump is a plastic piece that has a line from pump and 3 outlets. 2 are going to the 2 carbs and the third is running to the motor. is the third line dumping in bottom cylinder? does that need capped off? I'm calling the shop in the morn, but curious if I might be onto something.

 

[racerone]

Sounds like you are describing the electric primer valve.----That item replaces choke flappers on the motor.----It is used for starting the motor.---Ask the shop how that works !!

 

[smoses99]

not electric, just a plastic adapter for the fuel lines, acts like a splitter.

 

[smoses99]

part 395540

 

[racerone]

One of the 3 outlets goes to the electric primer valve I believe.----The other 2 feed the carburetors.

 

[smoses99]

ahh, ok gotcha

 

[juno pierrat]

any progress? any updates?

 

[smoses99]

still not right, not going back to that shop so started some stuff myself. changed ignition coil, found small crack in housing, it is filling the water barrel with an oil layer, gotta think it's all fuel related now, do these lines look like they are running to the right place? the top line of the bottom carb feeds the choke. the three coming off the splitter is what I'm wondering is wrong

 

[racerone]

The " splitter " as you call it gets fuel from the fuel pump on the side of the block.-----2 of those feed the carburetors and one feeds the electric primer valve.-----The 2 wee lines come off the primer and go to the top of each carburetor.--It does not get any simpler than that.----Post a picture of the red lever on the primer valve in the " run " position.-----What other trouble shooting has been done ??