82' 115Hp Johnson, dies after running a bit

[vintage_car]

I'm totally new to this bass boat, for that matter boating in general. I;ve rented a few pontoons, and many years ago had a small v-hull with a 4HP motor on it. Big upgrade to me.
The engine runs great, fires up quickly after being out of the water. After a couple hours of boating, jumping from a couple spots on the water, the engine will not fire. I have to lift the choke, push the key in and out and feather the choke/fast idle. It smokes some after it fires up, but if I let it sit at that fast idle for a minute or so then lock it down into run and engage the engine it will go again. I also noticed it die after a long idle through a no wake zone returning home and waiting for the trailer to be backed into the water. It just died and was a real pain to get started again.
The next day in the water though it fired up on the second turn of the key...

Where do I start?

 

[bktheking]

Re: 82' 115Hp Johnson, dies after running a bit

What service have you performed? Carbs been cleaned, fuel system looked at as far as filter/lines? How's the battery in the boat, up to spec? A boat that dies either loses fuel or spark or has compression issues. How about compression, put a gauge on it and check all 4 cylinders.

 

[vintage_car]

Re: 82' 115Hp Johnson, dies after running a bit

battery is brand new. I have not preformed any service at this point nor do I know how to at this point. I'm a decent shade tree mechanic on cars so I figure I can do some of this work myself. as for testing compression- do I need water running through it?

 

[bktheking]

Re: 82' 115Hp Johnson, dies after running a bit

Nope as the motor will not be running for the compression test. As a starting point a good OEM manual will get you started. I'd start by testing compression, look under the "top secret" post at the start of this forum, it describes what to do.

I guess my confusion you state:

After a couple hours of boating, jumping from a couple spots on the water, the engine will not fire.

Are you restarting after a couple of hours of sitting on the water?

 

[emdsapmgr]

Re: 82' 115Hp Johnson, dies after running a bit

Dying out after idling for a long time can be due to a low idle. The engine should idle between 650 and 750 rpm, set when in gear with the boat floating at normal level in the water. Any idle lower than this can cause the engine to slowly die out as you describe.

 

[vintage_car]

Re: 82' 115Hp Johnson, dies after running a bit

is there a way to adjust that idle? Is it simple carb tuning or an adjustment elsewhere

 

[vintage_car]

Re: 82' 115Hp Johnson, dies after running a bit

Nope as the motor will not be running for the compression test. As a starting point a good OEM manual will get you started. I'd start by testing compression, look under the "top secret" post at the start of this forum, it describes what to do.

I guess my confusion you state:

After a couple hours of boating, jumping from a couple spots on the water, the engine will not fire.

Are you restarting after a couple of hours of sitting on the water?

yes after sitting a couple hours.

 

[bktheking]

Re: 82' 115Hp Johnson, dies after running a bit

Well then, motor would be cold by that point so a cold start procedure would be in order, if you shut it down for 5 minutes then a turn of the key without choke or fast idle lever would work but 2 hours is totally different. As far as dying out EMDSAPMGR has a good suggestion, do you have a tach on the boat? If so what is idle rpm after warm?

 

[vintage_car]

Re: 82' 115Hp Johnson, dies after running a bit

I know I have a speedo- but it doesn't work, not sure I have a tach...brand new boat to me... only been on water 2 times. if it does have a tach, I doubt it works.
the only guage that seems to work is the tilt/trim guage. The fuel guage dances all over the place.

 

[emdsapmgr]

Re: 82' 115Hp Johnson, dies after running a bit

There is no carb adjustment for idle on that enigine. There is a big screw on the spark advance lever which will adjust the idle timing which adjusts the idle rpm's.