2006 Johnson 15 HP 4 Stroke bogs when snapping throttle

viper1216

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Looking to pick up an engine from a friend and having some issues with it. When I originally got it, it would not go to full throttle at all and would stall. I replaced the plugs, fuel filter, impeller changed the oil got a new tank and replaced the bulb and line. Checked compression and even across both cylinders. Didn't write it down but want to say about 100-105 on both. Still having same issue after so took off and cleaned the carb. When doing so. I did find the high speed circuit appeared to be stuck in the down position. Took that out, and there was some gunk on it, and in the port where it sits. Cleaned it all out and put back together, and circuit moved freely. Now I am able to bring it up to full throttle slowly and appears to run fine, however, if I snap the throttle, it still bogs down and will stall if I leave it there and don't back off. Engine appears to run well other than that. It was a good deal on the engine, but also don't want to buy a problem motor. It seems some items are a unavailable for it....so same thing, don't want something I can't get parts for. And I do know this is basically a rebranded Suzuki engine...I have looked up parts for both Johnson and Suzuki. I'm leaning towards fuel pump, but since I have already put a decent amount of money in this thing, I don't want to sink more in unnecessarily. I did take the pump off and apart and did not see any gunk or crap on it. It appears to be a mechanical pump, there is a cam type thing on the back and it seats into the engine. Anyway to test this for flow or something? I think I found a pump for about $100...not 100% sure it is the right one and would need to research a bit more, but it looks correct. I am already over $300 into this thing already though, and it's not even mine yet lol. So again, if I can test and confirm first that would be great. Or any other suggestions to check greatly appreciated. Thanks so much!!!!
 

Crosbyman

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normally if the pump was bad simple hand pumping fuel should refill it and carb and prove the pump is bad...have you tried ?
 

viper1216

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normally if the pump was bad simple hand pumping fuel should refill it and carb and prove the pump is bad...have you tried ?
I actually was down today and tried that. Pumping the bulb didn't seem to make a difference, however the bulb does seem soft which I found kinda weird.
 

Crosbyman

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I actually was down today and tried that. Pumping the bulb didn't seem to make a difference, however the bulb does seem soft which I found kinda weird.
the bulb never gets " hard" as it is subjected to negative pressure from the fuel pump.
 

viper1216

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the bulb never gets " hard" as it is subjected to negative pressure from the fuel pump.
Ahhh ok that makes sense. So with squeezing the bulb not making a difference would that mean fuel pump not likely the culprit? I was messing with it earlier and if i snap the throttle from idle, it bogs and dies. However if I bring up slow and then start snapping the throttle it seems fine. So only going from idle to open throttle is there an issue.
 

Crosbyman

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the bulb becomes hard again only if you pump it up and a full carb stops further inlet of fuel with the inlet needle/float ( works like a toilet bowl) . if the fuel does reach the carb to fill it up with other no benefits the pump is likely ok. now look for carb or ignition problems .

check for good sparks clean barb and check exhaust passage for blockage....the engine needs to push out exhaust so new air-fuel mix can come in !
 
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viper1216

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the bulb becomes hard again only if you pump it up and a full carb stops further inlet of fuel with the inlet needle/float ( works like a toilet bowl) . if the fuel does reach the carb to fill it up with other no benefits the pump is likely ok. now look for carb or ignition problems .

check for good sparks clean barb and check exhaust passage for blockage....the engine needs to push out exhaust so new air-fuel mix can come in !
There is a bunch of motion in the water behind the engine when run it so I would think exhaust is good. Ill have to check the spark next see if its pushing a hot enough spark but i feel like that would make it skip a bit.
 

cyclops222

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The SLOW opening of throttle to WOT. Could be a fuel flow pumping problem. Replace that mushy fuel bulb. See if that affects a quicker response while being squeezed.
 

viper1216

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The SLOW opening of throttle to WOT. Could be a fuel flow pumping problem. Replace that mushy fuel bulb. See if that affects a quicker response while being squeezed.
It's a brand new bulb. I replaced the fuel line, bulb and fittings when I got it. Could it still be crap and new? I still have the old one I can throw on there.
 

cyclops222

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Why do you have to SNAP the throttle open ? Is that a normal way to accelerate a normal motor ? Have you checked the operation and condition of the Reed Valves ?
 

flyingscott

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Early 4 strks, especially early 2000s had the idles leaned out to pass emissions. The idle Jets were extremely prone to plugging and being difficult to clean. They also were leaned out to pass Emissions and that will also cause a bog.
 

viper1216

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Why do you have to SNAP the throttle open ? Is that a normal way to accelerate a normal motor ? Have you checked the operation and condition of the Reed Valves ?
Could be lots of reasons to need to go to full throttle....this is on a small rubber inflatable....i could be tooling along at idle or just above and need to get the hell out of the way of some larger craft....instinctively I am going to hit the gas....and it is going to stall. So no, not normally I am fine bringing up slowly, but it is clearly not running like it is supposed to and I want to fix it.
 

viper1216

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Early 4 strks, especially early 2000s had the idles leaned out to pass emissions. The idle Jets were extremely prone to plugging and being difficult to clean. They also were leaned out to pass Emissions and that will also cause a bog.
Thanks for the insight!! Wonder if I should pull the carb off again and maybe put a torch tip cleaner through the idle jet.
 
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