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35 HP Mercury not running normal

J

jkamper21

New member
"I have a 35 HP Merc, about 20

"I have a 35 HP Merc, about 20-22 yrs old. Lately I've noticed that when I start it(manual start) it never seems to "rev" up all the way like normal. When I put the throttle at idle it almost always dies on me. If it stays running it runs like crap, meaning it sounds like it is not fully running.

When I turn it to full throttle I go about 3-5 mph and it is really slow. Normally at full throttle I can move pretty fast. The motor just doesn't sound the same when it runs normally. I took it to a Certified Merc. dealer and after 135.00 dollars he told me it ran fine for him and he could not locate a problem. Every now and then it acts this way but usually if I shut it down and re-start it it runs fine.

Any help would be appreciated."
 
"Don't think it is bad gas

"Don't think it is bad gas since it was pretty fresh, a week old. Vent was open on gas tank. Could be cylinder or clogged fuel filter?"
 
"its running on one as Jeff sa

"its running on one as Jeff said. Could be the carb flooding and taking out the bottom cyl or its ign. Safest thing to do before you spend money is check the compression then spark. You can use a timing light to check spark while its running, just move the probe. To check the carb for flooding, with engine off pump the bulb, anything dripping out is bad."
 
"Thats what I thought. One thi

"Thats what I thought. One thing w/ my motor is it drips gasoline from the carb, I was told that is what that model does. It's about 22 years old and the Merc. repair guy said that is what that particular carb does.

Not too good w/ motors, but how do you check the compression? I do not have a timing light either.

Is this a big expense?"
 
"Find another mechanic! The c

"Find another mechanic! The carb needs a rebuild, but you might have another problem. Pull the lower plug when it screws up and check for water droplets--they bead up. If so, your exhaust plate may have a hole corroded through it--common problem on those motors--or a bad lower seal.

Jeff"
 
"I got it fixed it was the swi

"I got it fixed it was the switchbox. Thanks for all the help.

Anyone know where to buy a front bow stop? I've looked all over and I can't find them. Mine is bent and I don't want it to break.

Thanks,

Jeremy"
 
..."Anyone know where to b

..."Anyone know where to buy a front bow stop? "

Explain better what that is?

Jeff
 
I tried to post a pic. but eve

I tried to post a pic. but every time it exceeded the size limit. It is on the front of the trailer where the bow stops(by the bow stop roller.) If you want I can email you the picture. The bow stop itself is held by two metal brackets and those are bending.

Hope that helps
 
"I have the same kinda motor&#

"I have the same kinda motor(35hp merc) and my pronlem is after it warms up it idles fine and it runs at a low speed fine but 5-10 sec after i go to full throttle it dies. I've changed the gas tank, it's vented, new hoses, new bulb, new fuel pump, gonna try new plugs but not convinced that will work either! HELP going to Minn. for fishing trip in 1 month!!!!!!"
 
"Sounds like its sucking air i

"Sounds like its sucking air instead of pumping fuel, try pumping the fuel bulb and see if it runs at full throttle while you pump. Also check the fuel line in the tank, see if its split or cracked. I have 2 of these engines, great little guys, keepthe starter tight on the mount."
 
"Tried pumping bulb while full

"Tried pumping bulb while full throttle, it gets a little boost but eventually dies. Motor runs fine hooked up to hose and ears, only dies when in water with load. Also as I said before, new gas can(plastic now, was metal?)"
 
"if you pump the bulb and cont

"if you pump the bulb and continue to pump the bulb will it run at full? That would indicate a fuel supply problem. They all sound good on the hose. You didn't say you cleaned the carb or set the float. I have the info at another comp. But, remove the 7/16 brass cap at the bottom of the carb. Directly behind that is the main jet, blow it out and if you find anything remove the carb for cleaning."
 
No it still cuts off but i&#39

No it still cuts off but i'm still feeling the fuel system problem. I did put a little carb cleaner in the fuel 9-05-09 didnt help. I'll try the carb thing thanks for the input so far.
 
"dont want to run carb cleaner

"dont want to run carb cleaner with the premix it changes premix calculation drasticly.lowers oil viscosity@engine compression.not to mention octane rating.timing and throttle syncronization could be the problem although fuel seems to be an issue also.try using more oil in your premix.its an older model!borrow a leak down tester for cylinder compression testing.this will let you know how quickly your losing compression.may have broken rings,bad gaskets,cracked cylinder wall etc..lower crankcase seal could also be shot.in that case water could be the problem.do you use a fuel seperator?its a good idea if you dont have 1.waters in all fuel this just keeps the majority from entering into carbs."
 
"I think you're on to some

"I think you're on to something! Today i put a new gas filter on and emptied gas can and put fresh mix in, took it to the river and while full throttle i noticed water blowing out of exhaust. I know it probably does this a little but like rain hitting water? enough to fill up my palm in as long as it will run?"
 
"When you're stopped some

"When you're stopped some exhaust/water spray will come out the two relief holes up high. The amount of water increases with the depth of the engine, its really just a pressure relief for the exhaust since you're not moving. For fun you can put your finger over the 2 holes when idling, makes a nice bubble show behind the prop where the exhaust normally exits."
 
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