Johnson venom 225 issues

**flabum1017** · 06-11-2021, 10:49 PM

Starting to sound a lot like vapor lock.... how old is the fuel, when did you buy the fuel? Winter fuel in summer will do that.

**Jakester136** · 06-12-2021, 03:42 PM

Originally Posted by flabum1017

Starting to sound a lot like vapor lock.... how old is the fuel, when did you buy the fuel? Winter fuel in summer will do that.

brand new fuel, drained the tank to run pre-mix last week

**faztbullet** · 06-13-2021, 05:32 AM

Make sure filter in primer is clean

**flabum1017** · 06-13-2021, 09:17 AM

What's the outside temperatures when you ran the boat? Did you try hitting the primer as it was bogging? Another thing that come to mind would be the fuel pump diaphragm. could be blowing up like a balloon with heat soak then contracting when the cooler fuel hits it. If you hit the primer bulb while it's bogging and force the fuel past the pump and it comes alive, that's a possibility.

in your original post, you said you are getting spark to all six, did you test it with the problem happening? Have you put new spark plugs in?

**Jakester136** · 06-14-2021, 09:50 AM

Originally Posted by faztbullet

Make sure filter in primer is clean

thanks will check today and also going to inspect the fuel pump

**Jakester136** · 06-14-2021, 09:53 AM

Originally Posted by flabum1017

What's the outside temperatures when you ran the boat? Did you try hitting the primer as it was bogging? Another thing that come to mind would be the fuel pump diaphragm. could be blowing up like a balloon with heat soak then contracting when the cooler fuel hits it. If you hit the primer bulb while it's bogging and force the fuel past the pump and it comes alive, that's a possibility.

in your original post, you said you are getting spark to all six, did you test it with the problem happening? Have you put new spark plugs in?

new plugs, burning clean not fouling now. No I haven’t been able to check spark while problem happening. Also priming bulb while it happens seems to have no effect and if I push The key in to choke there’s no change

**flabum1017** · 06-14-2021, 11:21 AM

You can take the front cover off the airbox and the pulse hose off the fuel pump, pump up the primer ball hard and see if there is any fuel dripping out the pulse hose from the pump and look to see if any of the carbs are flooding over.. Does your motor have quickstart? if it does, is it working properly? Set the timing and link and sync with it warmed up.

On the ignition, you'll want to check the spark when it's happening. run it out, shut down like you normally do then putu your spark checkers on it when you know it's going to bog. Will need two people for this. If you can't get it to bog doing this (the cowling being off), then we might be back to vapor lock or even an exhaust leak getting under the cowling.

**Jakester136** · 06-14-2021, 11:42 AM

Originally Posted by flabum1017

You can take the front cover off the airbox and the pulse hose off the fuel pump, pump up the primer ball hard and see if there is any fuel dripping out the pulse hose from the pump and look to see if any of the carbs are flooding over.. Does your motor have quickstart? if it does, is it working properly? Set the timing and link and sync with it warmed up.

On the ignition, you'll want to check the spark when it's happening. run it out, shut down like you normally do then putu your spark checkers on it when you know it's going to bog. Will need two people for this. If you can't get it to bog doing this (the cowling being off), then we might be back to vapor lock or even an exhaust leak getting under the cowling.

OMG I’m not sure how I didn’t see this, previous owner had primer solenoid plumed in on the vacuum side of the fuel pump! Unless I’m crazy there’s no way that can work it will be sucking the fuel out of the primer, primer fuel line has to be on exit side of the fuel pump correct

**Jakester136** · 06-14-2021, 08:56 PM

Originally Posted by flabum1017

You can take the front cover off the airbox and the pulse hose off the fuel pump, pump up the primer ball hard and see if there is any fuel dripping out the pulse hose from the pump and look to see if any of the carbs are flooding over.. Does your motor have quickstart? if it does, is it working properly? Set the timing and link and sync with it warmed up.

On the ignition, you'll want to check the spark when it's happening. run it out, shut down like you normally do then putu your spark checkers on it when you know it's going to bog. Will need two people for this. If you can't get it to bog doing this (the cowling being off), then we might be back to vapor lock or even an exhaust leak getting under the cowling.

ok, so now that I have a functioning choke, I was Able to get to the lake for a test run today, cold starts easily with just a little choke. Ran a few circles around the lake to warm the motor up and came to a spot and stopped for 15 minutes, once I fired it up, and get ready to take off, same thing wants to fall on its face, the good news, feeding it a few pulses of choke snaps it out of it and it takes off and runs strong for as long as you want and idles great. So that pretty much narrows it down to a fuel deliver issue right? Either I missed something in the carbs or the fuel pump is weak?

**flabum1017** · 06-14-2021, 10:34 PM

Do you have an anti-siphon valve on the fuel tank? Check your fuel tank vent to be sure there isn't an obstruction..... down here, we get mud doggers that build nests in fuel tank vents..... I'm still thinking vapor lock.... high vacuum on the inlet of the fuel pump and hot temps can cause this. You can put a vacuum gauge on the fuel line just before the fuel pump and see what you get.... anything over 4 - 5 inches of vacuum means there is a restriction. 3 inches is about normal with an anti siphon valve on the tank.... close to zero without one. another quick way to see if it's vapor lock is to leave the cowling off and see if it helps.

If you had a problem in the carbs, I would think you would be running real lean even when it's running "good"

Then there's those darn spaghetti seals behind the carbs.................

**Jakester136** · 06-15-2021, 07:46 AM

Originally Posted by flabum1017

Do you have an anti-siphon valve on the fuel tank? Check your fuel tank vent to be sure there isn't an obstruction..... down here, we get mud doggers that build nests in fuel tank vents..... I'm still thinking vapor lock.... high vacuum on the inlet of the fuel pump and hot temps can cause this. You can put a vacuum gauge on the fuel line just before the fuel pump and see what you get.... anything over 4 - 5 inches of vacuum means there is a restriction. 3 inches is about normal with an anti siphon valve on the tank.... close to zero without one. another quick way to see if it's vapor lock is to leave the cowling off and see if it helps.

If you had a problem in the carbs, I would think you would be running real lean even when it's running "good"

Then there's those darn spaghetti seals behind the carbs.................

all good advice, i will check fuel vent, I don’t have anti-siphon just a drop tube. I will try it without cowling today and report back, last time I did that I had to be careful not to fill my motor with water when coming down off pad . I did notice fuel filter stays full when motor is off, but only about 1/4 full when running. I pulled fuel pump apart last night just to inspect, looks fine. If it is vapor lock how do you tackle that one LOL

**racer** · 06-16-2021, 05:51 PM

Sounds like heat soak and these are known to do this. First richen idle mixture 1/4 turn next when you go to refire the engine do it like when cold with a little throttle and hold primer in for a couple seconds return to idle and it should now take off like it should.

**Jakester136** · 06-20-2021, 10:24 AM

Originally Posted by racer

Sounds like heat soak and these are known to do this. First richen idle mixture 1/4 turn next when you go to refire the engine do it like when cold with a little throttle and hold primer in for a couple seconds return to idle and it should now take off like it should.

Ok so more playing around with the boat and same issue, I dont Think it’s heat soak because it will do it from the very beginning of the day now before it’s even warmed up, I have to feather the choke a few times while lightly applying throttle and it will take off. I have played with idle/air screws tried 5 turns out, 6 and 7. They initially were at 8.5 turns out which seemed too lean. I’m about to start at 2 turns out and slowly increase it out to 8 turns and see if any setting makes any difference at all. Also I’m going to put fender washers on the carb side plates today, I just learned that I should do that after reading thru this forum. If that doesn’t work all the carbs are coming back off for another rebuild. Funny part was it actually ran a little better when I had My idle timing backed off to 6 degree’s ATDC, and the idle screws were 8 turns out. Since then I increased idle timing to 4 degrees ATDC and max advice to 18 BTDC. I just don’t understand since adding choke would imply I’m not getting enough fuel but runs a little better when I back Out the idle screws which I believe is leaning out the carbs. Still runs like a beast on top end will spin a 24 raker past 6k rpm if I let It and push my boat to 75 mph just really annoying not being able to hit the throttle and go.