175 johnson running rough

[bg175]

Starts right up, idles fair, but after warmup dies when you throttle up in gear. Put it in neutral, give three good rips of the throttle, put it in gear and it runs fine. would this be the high speed jets? Already checked compression, spark and so on. Can you help me?

 

[Molaker]

Re: 175 johnson running rough

What's the idling RPM - in neutral and in gear? It does not sound like high speed jets, more like low speed and/or idle setting.

 

[bg175]

Re: 175 johnson running rough

neutral idle, 650 to 700, in gear bout 500. but the problem doesnt start until i try to accelerate from idle while its in gear. Its like its starvin for fuel. could it the advance trigger, or dirty carbs?

 

[Molaker]

Re: 175 johnson running rough

My book gives idle RPM as 600-700 RPM with no statement as to whether or not it should be set in gear, but it is a Seloc manual... Most recommendations on this forum have been to set to that RPM in gear, so you may be a little on the low side. But, assuming idle speed is acceptable, I suggest first checking to see if pumping the primer bulb just before sticking it in gear makes any difference. If so, then you may have an air leak in the fuel line or maybe a weak fuel pump. Otherwise, it does sound like a good carburator cleaning would be in your future. Once you come off idle and get past the stumble stage, you indicate that it runs okay. If that means it seems to have normal power coming up on plane then I don't think it would be a timing advance problem or a high speed jet problem.

 

[tashasdaddy]

Re: 175 johnson running rough

you don't state model and year. some have mid range jets, also.

 

[bg175]

Re: 175 johnson running rough

sorry bout that, It is a 1977 175, as soon as it "trips and stands back up", it planes out very quickly! So that may eliminate the advance question?
Is the fuel pump behind the screens on the fuel lines, and is it mechanical or vacuum? Thanks

 

[Molaker]

Re: 175 johnson running rough

Actually, it's a new one on me, but it looks like that motor has 2 fuel pumps that operate in tandem. Just follow the fuel line from where it comes into the motor housing up to the motor. You should be able to find them (or it). I recommend you get a good manual, preferably OEM. The fuel pumps are "pulse" operated in that the diaphram is pushed in and out by pressure/vacuum from the crankcase (at least I think that's the way they operate).

 

[modsrx]

Re: 175 johnson running rough

souds like your carb doesnt work good !!!!!

 

[bg175]

Re: 175 johnson running rough

Ok, pulled carbs off for cleanin, but there was no need. All three were spotless on the inside, cleaned them anyways! Here's the deal now, should the advance move to the bump stop before the butterfly's open, or should it be gettin there at the same time when they begin to open? If the butterfly's open before full advance, would'nt that cause the motor the stumble under load? It does on a 350 chevy!


Tell me what you think please?!!

 

[bg175]

Re: 175 johnson advance issue

Re: 175 johnson advance issue

after attempting to clean carbs, they were spotless inside by the way, watching the linkage movement i noticed that the throtttle was opening before the advance was all the way forward "on the bump stop." Would that cause the engine to stumble under load? If so, where does the advance need to be when the throttle opens?

Who can help?

 

[HighTrim]

Re: 175 johnson running rough

To synchronize carb and timer linkage:

Adjust idle adjustment screw so motor will idle at 650 max rpm IN GEAR

Open throttle to wide open (upper carb throttle shaft roll pin against its stop) Adjust wide open throttle stop screw so that throttle valves are full open without strain on throttle shafts.

A strip of thin paper between the roll pin and stop should pull out with just a slight drag.

Idle engine 15 secs minimum in neutral and 15 secs min in forward gear after all engine adjustments are made. Check for flooding and leanness-accelerates rapidly after time has elapsed in froward gear and check for loading.

Throttle and choke linkage:

Retard throttle lever until throttle cam follower roller does not touch cam. Loosen upper and lower carb lever adjusting screws tgo allow return springs on throttle shafts to close throttle valves. Rotate levers manually to make sure valves are closed. Tighten screws. Start engine and run at idle speed (throttle closed) Snap out throttle link. If adjustment is correct with engine idling, RPM should not change.

Loosen carb choke rod fastener lock screws. Place manual choke lever in choke "ON" position. Manually close the other two choke valves and tighten screws.

 

[bg175]

Re: 175 johnson running rough

how bout the advance lever, when should it be touchin the bump stop in the advance postion? thanks

 

[HighTrim]

Re: 175 johnson running rough

Bottom mark on throttle cam should align with center of cam follower roller as roller makes contact with cam.

Align bottom mark on throttle cam with center of cam follower roller. Loosen carb cam follower screw. Move arm to close throttle valves and re tighten screw.

Warm up lever on remote control and start mark on throttle cam must be aligned.

The throttle cam on engine is marked START. When warm up lever on control box is moved to START position, the START mark on throttle cam should center on cam roller. If it does not, turn the stop screw in your control box in or out depending on which way it moves it to get it right. Warm up lever adjustment should be checked and re done when the engine idle speed is changed enough to require throttle cable trunnion adjustment.

 

[modsrx]

Re: 175 johnson running rough

if the timming do not advance the only thing it will do it will make your engiine run without power....... not sure if they have iddle ajust screw on those carb make sure they are not to close if they have some.. its not a 50 hp you got there so ...take a good look at those plug to see if they are all the same color ....not sure how mutch carb you have on that motor but if u wanna try something take the air box off and try to inject some fuel in carb went the motor do the problem u will see if it gain power of if its worst....if its gain its because the circuit iddle midrange is to lean ...but its sounds like u have a something not running good in carb... does it feel like every cylinder have a mist or only 1 or 2 ???make sure u have a big spark at your plug cause went u ask for power u need nice spark or the engine will mist

 

[jtexas]

Re: 175 johnson running rough

Don't know what it means for a cylinder or an engine to "mist", but if the throttles open before the timing advances, the engine will die if you try to accelerate quickly, but you can usually ease it on up to full throttle. The timing advance lever usually hits the stop well before WOT.

Joe Reeves procedure for setting full spark advance:

(Timing At Cranking Speed 4?)
(J. Reeves)
The full spark advance can be adjusted without have the engine running at near full throttle as follows.

To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).

Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4? less than what the engine calls for.

I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28?, set the timing at 24?. The reasoning for the 4? difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4?.

If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4? which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.

No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.

Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.