1979 75hp stinger rough starts/idle

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

I put soft wire through those channels and blow high pressure carb cleaner through, often you get muck suddenly spurting out the otherside that you would of thought could never of existed in there.


Yep a timing light would be good to check whether there is a missing spark at misfire. But hopefully the carb clean of the orifices and channels will of fixed it.
If you still have the misfire post a video if possible as its sometimes easy to tell by listening and watching it as to what is causing it electrical or fuel

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

I tore it all down again today and spent about an hour on each carb. Cleaning every passage as best as possible. There are still no signs of any blockage as the carbs are superbly clean to begin with.
Here are some pics of the carb before I cleaned it. Very clean and looks to be recently rebuilt or gone through.
The only areas I cannot get around are these caps. I suppose I can order a rebuild kit, pull them out and clean behind them.
No change at all in the way it is running. I did fine a pin hole in one of the fuel lines. Replaced lines at the carb with new hose. The rest of the fuel lines look fine.
Carbs before cleaning:



Here is a video. Watching it back I can now also hear what sounds like spark knock on one cylinder along with the lean sneeze and poor idle/stalling




For anyone not updated. Compression is 145 across all 3 cylinders. At one point one of the ignition coils had no spark but since has good spark. I have checked 4 times and it is still jumping a good spark. I have cleaned the carbs twice now. All seems well, floats are in great shape, needle seats are in great shape and no signs of any clogs. Motor runs great at higher rpms but does not like to idle. It does not help to prime the fuel bulb during stalls either.
Have not checked timing yet

I did notice during another test not shown that during the lean sneeze the upper carb spits fuel vapor out. Which is the same cylinder the coil tested no spark a while back. I need to hook it up to a timing light during these misfires and see if it the coil failing.

Any other thoughts?

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

You could try pulling each sparkplug wire out in turn and grounding it and seeing if that helps isolate it down.
After that i suppose you will need to check timing, timing way out can cause a bit of a back spit from a carb

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Thanks. I'll get it timed soon. Hopefully that is it.

Is it ok to run my boat without the silencer? Or will that cause a lean condition.

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Thats fine to do

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Full throttle run on the lake this morning. Click for video
Think it is lacking a bit of power but is running good up top.
Pushing 2 guys in a 15' seaswirl

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Seems ok there, powered up with no hesitations, nice flat water too.
How did it idle

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

It idles down good for about 1 minute after a full throttle run. Any longer than 1 minute and it starts to sneeze. After sitting and fishing a hole for 30 minutes, it is hard to start again and does not like to idle. I have the timing light, won't have time to go over it until tomorrow sometime. Gotta get it figured out soon the salmon are going to start running in a week or 2!!

I'll have to bring the gps out there. I'm guessing were going about 32-35ish. I would think the 75hp could push a 15' fiberglass into the 40+ range. Although I don't know what prop is on it. It was on a larger boat before it's swap onto mine.

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Anyone know where I can find a manual for this engine with link and sync procedures? Going to go over timing as well.
Also, again very new to this. How do I know if I have a fast start feature?
Thanks

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Quick start? Didnt come out til 1988, its the same age as Rhianna

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

lol. thanks
Just reading over timing procedure write up.
They need a write up for noobs/dummies. I don't quite understand considering I'm not familiar with the engine at all. A manual would be my better bet I'm sure so I'll probably wait until I can get my hands on one.

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Can someone point me in the right direction as to where I can find a service manual?
Can't seem to find one but not exactly sure where to look. Does not have to be online or free but preferred.

Thank you

 

[phillnjack2]

Re: 1979 75hp stinger rough starts/idle

in that video the engine is no where near full throttle.
i would say by the sound its about 3/4 maybe less.
those stingers can rev high and they fly, have a real grunty sound to them as well.
that engine sounds more like a very restricted one by the throttle etc.
when your remote throttle lever is fully forward are the butterflys in the carburettors level ? (max throttle position)
there is no way that is getting max power in the video, i guess about 4000rpm maybe 4500 at a long push.
what does your rev counter tell you its getting ?
that should see 5500 to 5750 easy on that boat, and sound like a roaring 2 stroke not a smooth 4 stroke.
man that engine is too quiet to be on full song at max power.
youl know when it is revving, as it will sound much louder and crisper.

have a look at what numbers are stamped on the carbs and let us know, maybe this has had the proper stinger carbs
replaced for lower powered ones !!!! that realy dont sound anywhere near right.
that should easily punch a 13x19 prop to 5500 rpm on that boat with 2 guys onboard.
also check where the cavitation plate is against the hull bottom !!!! might be a touch too low.
just checked your vid again, definitely not revving .


phill

 

[phillnjack2]

Re: 1979 75hp stinger rough starts/idle

and whats with the spring pulling back the throttle lever ?
this should not be on there, its not meant to have that.
maybe someone likes the idea of having to keep one hand on the lever at all times.






phill

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Phil, thanks for the insight.
I've thought the same as well. Does not seem to be at full throttle and now that I think about it, it feels and sounds restricted. I'll take a look at the butterfly's next time I am out and see if they are opening all the way. I'm just not that familiar with how they should sound so thanks for picking up on that. Also, in that video the silencer is not installed so it should really be making a lot more noise.
I don't have a tach yet. I know I need to get one in order to properly link /sync, set the idle and time it. I'm still pretty unfamiliar with the procedures.

Ive also thought that spring seems out of place. Where it hooks to the throttle linkage does not seem like something from the factory. It does not spring the throttle back either so I'm not sure what it is doing.
The throttle lever at the controls will engage the forward drive just as it is being clicked from the neutral position but does not see any throttle movement until about 3/4 of the way down. Then the lever reaches full extension and Ive just assumed that was full throttle.
The cable at the motor side is fully adjusted position. So I started to adjust it out the other way to see if I could get more movement at the lever/controls and it effected the idle so I put it back and left it alone. That seems to be an issue.

Thanks again. Bear with me. Pretty new but will pick it up eventually. I'll report back tomorrow what the carb numbers are and whether they are opening all the way.
Where can I find a temporary tach?
I am still trying to gather info on where to buy/find a service manual

 

[phillnjack2]

Re: 1979 75hp stinger rough starts/idle

yeah those stingers can realy get a move on.
they run a touch faster than normal 70hp, thats why a lot of the racers liked them.

you'l get there ok in the and and have a real nice engine .

phill

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Here are the carb numbers
323714 stamped on all 3 carbs.
However, there are numbers printed in ink on the float bowls. The top and bottom carb read 389242 and the center carb reads 389241
I checked the throttle lever and at full throttle the carbs are at wide open throttle. So in that video it by all adjustments was running at wot.

I also checked the cavitation plates. It sits about 1" above the bottom of the boat

The carbs were a little off sync. Not by much though. Upper and lower carb had about 1/32" left to close when it was at full closed position so I adjusted them just a little bit.

I still need to link and sync, check the timing and monitor spark while it is misfiring to see if a coil is weak/failing.

 

[Chinewalker]

Re: 1979 75hp stinger rough starts/idle

I didn't think the video sounded that bad. I have the same motor on my 15-footer, so I'm pretty familiar with the sound. Mine peaks around 5800 revs. Get a tach on yours and find out for sure...