New outboard. Am I being paranoid?

I just made by first boat purchase, not a big boat by any means. But big in my eyes. Its a Lowe 14/36 Jon with a livewell and a Brand new Mercury 4Stroke 15 hp. Manual start, short shaft. I barely have 2 hrs on it, and the tank was filled with 93 octane. I am in the "up to 3/4 throttle and run at full-throttle for short periods of time" section of the break in. But while in forward gear, from off-idle to maybe short of half, I can hear a slight RPM surge, not really noticeable, just enough to make you worry. Up and down, maybe 50 rpm..open it on up to 1/2 and on to full, its smooth as glass. And not a fast up and down, just a up...............down............up, barely makes you sway in your seat...barely. But just in that one throttle range its got me worried. This is also on straight smooth water, not turning. Do I just need to not worry? Get a tank of gas through it and some more hours on it?

Re: New outboard. Am I being paranoid?

I think everything is fine..continue the break in period..if after 20 hours it is still doing this you could ask your dealer to check it out ( I assume it will be under warranty). You could even call your dealer and see what they have to say about the surging. but my guess is it would fall under "normal".

Re: New outboard. Am I being paranoid?

Keep a close eye on the engine oil level -- not only during break in but every time you take the boat out. Don't rely on a sensor to tell you the oil level is low.

Re: New outboard. Am I being paranoid?

Get your breakin done. Go back to the dealer, have them drill out the welch plug over the idle mixture and fatten it up a bit. Pretty common with these motors right out of the box. Good luck!

Re: New outboard. Am I being paranoid?

Thanks for the help folks. I am assuming by fatten you mean make the mixture richer?

Re: New outboard. Am I being paranoid?

Yes sir.

Re: New outboard. Am I being paranoid?

Well yesterday i was out their cleaning the boat up, keeping it shiny and makin the mercury shine! And i messed with the tank vent, i noted that the two times i have taken it out i only loosened the vent cap a few threads, i didn't know i could back it out all the way and actually take the vent cap out sorta. So im guessing maybe that was the problem. We will take it out tomorrow and ill see. I plan on running it for a while tomorrow.

Re: New outboard. Am I being paranoid?

Michael_B said:

Well yesterday i was out their cleaning the boat up, keeping it shiny and makin the mercury shine! And i messed with the tank vent, i noted that the two times i have taken it out i only loosened the vent cap a few threads, i didn't know i could back it out all the way and actually take the vent cap out sorta. So im guessing maybe that was the problem. We will take it out tomorrow and ill see. I plan on running it for a while tomorrow.

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Isn't the vent cap suppose to be closed tight when your are running the motor? If so Michael it might be starving for fuel at that RPM that your hearing a surge and then decline? I wonder because a Neighbor gave me a Plastic Gas tank for my pontoon. He had two but said one worked better than the other so he gave me the one that worked the best. He then sold the other boat. I notivced the vent was loose. I assumed it was vented so the tank wouldn't swell in the summe rheat from pressure. But I would think the vent would have to be tightened when the tank is being used or the Fuel pump would be sucking too much air. Somebody tell me if I'm right or wrong.

Re: New outboard. Am I being paranoid?

ummm.... i am used to older outboards.... but...
with the exception of pressure tanks of old, I believe the vent should be only closed when transporting the tank.... open when stored and definitely open when in operation. the reason for the vent is to allow something (air) to take the place of the fuel that was drawn from the tank.... it also keeps the tank from swelling when heated and collapsing when chilled or cooled.
now if it is an old pressure tank with two lines or more going to the tank than the engine would pressurize the tank and that took the place of a fuel pump.....
as I understand this to be a 4 stroke engine... i would bet my left arm that it has a single hose coming from the tank and should therefor be vented....also it should be in the NEW engines manual....

Sean

Re: New outboard. Am I being paranoid?

Yes. Tank needs to be vented at all times except transport. If you close the vent, the pump cannot draw fuel from the tank.

Re: New outboard. Am I being paranoid?

I never close my vent screw on top of my 6 gallon tank. It never leaks or spills gas out of it. When you are driving the boat it's a lot more rockier on the water than when your trailering it.

Too many times when I thought I had to always keep it closed when not in use I'd be out on the boat again for the day I'd forget to re-open it. Then all of a sudden i'm cruising along and the motor dies because I forgot to open the vent.

The only time I close the vent now is when I'm back there drilling a hole or hooking up an electrical connection of some sort. And if I'm doing that I usually just take the tank out of the boat for safety. I don't smoke anyway or ever use a gas grill off the back of my boat

My Brother in law gave me that tip of not having to close the vent down each time. He said driving the boat with it open (which it has to be anyway) sloshes the gas around a lot more on the water than when you are trailering.

It also helps leaving it open when it's a full tank as it gets real hot in my driveway under the summer sun a plastic tank can swell up like it's going to burst when the vent is kept closed. Vent always open solves that issue. I don't top it off too high after refueling it anyway. It's actually a 6.5 gallon tank and I usually just put in 6 gallons leaving room for expansion.

I also always carry a spare 2 gallon tank in an up front locker in case I run the 6 gallon tank dry. This way I don't need a fuel gauge and can get back to the launch from just about anywhere with a 2 gallon backup, with my 40 hp 4 stroke.

Re: New outboard. Am I being paranoid?

Well folks! Took it out twice and its still there, from 1/4 to 1/2 throttle while cruising thru no wake zones, its surging up...down....up, enough my wife even noticed it. So I am about to call the dealer and schedule a trip down there.

Re: New outboard. Am I being paranoid?

May as well. The warranty that comes with your motor is part of the purchase price.

Re: New outboard. Am I being paranoid?

After I talked to the service tech at the dealer, and described the problem, he said that these outboards all search for the desired RPM in that band, from 1/4 to 1/2 throttle. Its just more noticeable on such a light boat.(145 lb hull weight). But if I wanted to, I could still bring it in, they would go over it. I got the 5 yr warranty from the promo so I have a while to see if it will work out...thanks all.

Re: New outboard. Am I being paranoid?

I have heard that also i wouldn't worry.My 25hp efi merc did that alot to.I think it just may be a normal thing on these little motors.

Re: New outboard. Am I being paranoid?

Michael_B said:

After I talked to the service tech at the dealer, and described the problem, he said that these outboards all search for the desired RPM in that band, from 1/4 to 1/2 throttle. Its just more noticeable on such a light boat.(145 lb hull weight). But if I wanted to, I could still bring it in, they would go over it. I got the 5 yr warranty from the promo so I have a while to see if it will work out...thanks all.

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If the dealer tells you there is nothing wrong with the motor, ask to go up one size in the pitch of the propeller. A larger pitch will help to "load" the engine a bit more considering the weight of the boat, and should help the RPM surging.