Johnson 150 Throttle Probs

[kbranden]

From reading the posts here, I am thinking it is a carb issue, but wanted to confirm because it seems my problem might be alittle different. I have a GT150 Johnson 1983. Out of the water, starts and runs fine both in gear and out of gear, pushing thottle sounds good.. etc.

In the water - Starts fine right off the trailer, can even push throttle forward, might get alittle hesitation, but usually goes to plane really well, sounds great running around the lake. You can immidiately lower it down to idle and it idles good, push forward on the throttle and you might get alittle hesitation at first, but will push it on up to plane.

Now, here's where it gets strange. Go fishing and troll around for an hour and then try it. Starts fine, but bogs down heavily to die when pushing throttle forward. In neutral sounds good.

Last night it even got worse, trying to get pass that bogging ended up where the engine then wouldn't even start. It acted like it wasn't even getting gas anymore or completely flooded. Tried waiting several minutes (which turned to hours and still no go). Thank God for 3 batteries because the 2 mile trolling back to the dock sucked.

We are thinking it is a carb issue. Your thoughts?

 

[oldcatamount]

Re: Johnson 150 Throttle Probs

So, are you trolling with the 150, or do you have a smaller motor for that?

 

[kbranden]

Re: Johnson 150 Throttle Probs

Using a bow trolling motor for that, the 150 not running. So, it seems to be alot worse after sitting in the water for awhile and then starting it up and trying to throttle up. Like I was saying, starting right off the trailer, it seems to do alot better with only alittle hesitation. But, let it set in the water for awhile and throttling up will just bog it down so bad you can't keep it from dying.

 

[oldcatamount]

Re: Johnson 150 Throttle Probs

Sounds like you might have a fuel priming issue. Maybe check for air leaks and loose clamps all the way back to the tanks.

 

[kbranden]

Re: Johnson 150 Throttle Probs

Yeah, we did change out the bulb yesterday, but this 'bogging' down happened before we did that change as well. We just never had it completely decide not to start like it did last night. We did notice that this new bulb never feels completely 'tight' after priming it. You can always seem to completely push it in to collapse.

 

[BreeOge]

Re: Johnson 150 Throttle Probs

I am Kbranden's Brother, also stuck out last night running the trolling motor back to the dock.

A note to add to what kbranden stated. When compressing the bulb, I have noticed it sounded as if fuel is getting pressed into the carb's. Could this be due to dirty carbs or bad fuel pump? The bulb never gets tight as I have seen with other boats as well.

 

[jonesg]

Re: Johnson 150 Throttle Probs

The float/valve isn't sealing the bowl, its flooding out.
Rebuild them all with new carb kits per the directions in your manual.
www.outboardbooks.com

 

[BreeOge]

Re: Johnson 150 Throttle Probs

Thank you, you confirmed what I thought it might have been! That is our next plan of action. Also thank you for the quick reply!

 

[kbranden]

Re: Johnson 150 Throttle Probs

We checked the carbs and they all seemed very very clean and working properly. We did find that maybe the choke was stuck and maybe has been sticking. We also did a compression check and they were about 70-75. Does that sound right for a 1983 GT-150 V6 Johnson???

 

[jonesg]

Re: Johnson 150 Throttle Probs

Its a bit low but compression guages are notoriously inaccurate.
The good news is they are all even.
You could try a seafoam decarb, if it has never been decarbed it needs it.
Its in the FAQ file.

My 1994 V6 is 85psi but it was 75 psi before I soaked it with seafoam.

 

[emdsapmgr]

Re: Johnson 150 Throttle Probs

When the engine won't start, check each plugwire for strong spark. A spark tester or inductive timing light will show the quality of spark on each wire. I would expect the compression on that engine to be around 90-95 lbs. Agree on decarbing the powerhead.

 

[kbranden]

Re: Johnson 150 Throttle Probs

Well, we are hoping that that it was a sticky choke. It runs great now (out of the water), the test will come when we put it in the water of course. We pulled the carbs off and inspected them and according to the bro, they look great and working. I've read here that you really can't tell that just by visual inspection so if it is still bogging when giving it some throttle in the water, I will get the kits and do it myself if needed. Although seafoam also seems to be a must as well.

 

[BreeOge]

Re: Johnson 150 Throttle Probs

The engine wouldn't start, it acted like it was not getting any fuel, and the spark was fine on all cylinders. After looking around for a bit, I decided to put the fuel assist into manual, and pump the bulb once or twice. After doing that the engine fired right up and ran rough. I proceeded to taking the carb's apart looking for any dirt, grim or other problems carb's have. Everything in the carb?s looked almost new. Not a speck of dirt that I could tell, all the flow holes were clean. I however just for good measure cleaned the needle and seat to clear any debris that I might not be able to see. As reading on here it looks as if a Re-build carburetor kit comes with rubber gaskets now, all the carb's have the rubber gaskets and look to have been in excellent condition.

Since the engine did not start until I turned the fuel primer to manual, I suspect that it may have been the problem. I did notice when taking it out of its mount, the electric connecter seemed to be gummed up a little; I cleaned it, and checked all the internal parts of the fuel primer.

After putting the carb?s and fuel primer back on, we noticed the fuel primer now clicks like it should when you choke the engine. This is something it did not do before, or at least we didn?t notice it making a noise.

This time with the fuel primer in run we tried to start the engine and it fired right up and ran like a champ. However the test will be when we get it back in the water today.

Also, I believe the engine does need to be decarbed, due to the amount of stuff I seen on just the spark plug when I pulled them out. I have printed off the FAQ for that procedure.