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Mercury 30 Hp Bogs out under load

G

gabed

New member
So I just got this boat with a 1999 Merc 30 hp 3 cylinder 4 stroke. It has apparently been sitting for 2 years, but I got a smoking deal on it, so I took it without taking it out on the water.

Basically it runs awesome when it's in a tank or in neutral on the water, and it will rev normally when I put it in gear until 1/3 throttle. Then it bogs down and dies. I have cleaned the carbs thoroughly, replaced the plugs, fuel filter, and gas. The old plugs were dry and black, and after about 15 minutes of running the new plugs (at 1/3 throttle) they had dry black on them also.

My fuel primer bulb and fuel pump seem to be alright because pumping on the bulb while driving doesn't change any of the engine performance at all.

Any ideas? How would I know if the plugs weren't getting enough spark? I can check for spark, but don't know how to measure the amount of spark.
 
Yes sir,what guyjg said.To test your spark you can buy a spark guage at autozone,ect.You need to find out how far your spark should jump on the mercury!!But yet if you ground out the spark plug to block and get a good blue color fire then you should be good.
 
Ok. Well I will test the spark tomorrow.
On another note, I had heard that I should check / replace the fuel line, so I took it off and cut it open since I'm going to replace it anyways. The interior lining was not attached to the hose... so could the lining be flattening when I increase the fuel demand (like when you try to suck a milkshake through a straw that's too weak)?
 
Well apparently it wasn't. I replaced the fuel line and the primer bulb, and there was absolutely no difference. My bulb was going a bit soft when I was driving the boat, but when I pumped on it there was no change in performance.

I think that I will clean the carbs one more time, but after that is there anything more to do with the fuel system? I'm beggining to think it's electronic.
 
Your primer bulb will get softer after you start it.The bulbjust gets gas to the engine and then once it starts,it will soften up.Does the engine smoke alot when it is at idle?Check the timing,and make shure your carbsare opening all the way when you put it in full throttle.First pump your bulb up tight.then Tilt your engine up like you are going down the road,look inside carbs and pump up bulb and see if gas is coming out of carbs,If so then floats in carbs are not seating and causing it to flood.the reason i say pick up engine,is so you can see the gas if there is any easier,instead ofgoing into engine.Let me know.
 
The tubes in the carbs,or any where.If you see gas rebuild carbs.You should be able to see it coming out from engine up rite,but easier to see if tilted.It might be just enough of a leak thats hard to see.Dont give up we will figur it out!!oats can be a pain somtimes.Also you need to buy a manual for that engine.
 
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