loud pop on increase acceleration

ladycaptiva

Hi guys.  My son and I were driving about 3000 rpms and when he went to accelerate a little we heard this loud pop.  We both looked at each other and thought maybe something in the engine area fell (hopefully)  (we have a plastic carrier screwed to the floor in there to throw minutia)  The temp didn't seem to increase the rest of our ride (maybe a little higher then I thought normal at 163is.  I usually notice it hangs right at 160.  Upon returning I noticed it rise a little to 170 when I came off plane fast but it returned immediately (so impeller okay from reading).   My exhaust manifold was hotter to the touch then normal.  As I have been taught to see if I can hold my hand on them and this time I could not on the starboard side.  Any thoughts?  When the exhaust manifold clogs does it make a noise?  Thanks

aero3113

Could it have been a back fire? This usually happens when your timing is off and when you accelerate. That can also be the cause of the engine temp rising a little.

seadogs

Did you loose any power? A fuel filter or low fuel pressure will cause a back fire through the intake and warm exhaust from being lean.

girls2water

I guess it could have been a backfire. No loss in power, road fine for another half hour.   I have not heard a backfire on a boat so would be a new sound for me and I imagine that a little deeper in tone then this one was just from hearing cars. Sounded more metallic (if that makes sense). I find myself nervous about even going out again because of all I have read about the darn exhaust manifold being hot and that causing water to get into the system and ruining the engine with no good way to determine via gauges.  I guess I am going to take her out tomorrow and see how it goes.  It starts fine still.  Thanks for the feedback guys.

girls2water

Weird, my name came up under girls2water and I thought I signed up as ladycaptiva..now I see capt hello'd me as 'girls'  I find it hard to maneuver in here and find my questions a second time.  any hints on that would be appreciated as well.

rinker312

A backfire on a boat sounds very different than in a car. I am betting that is what you heard. You might be getting some water or something in your gas. I often get backfires in the beginning of the season when running old fuel through that may have some water in it.  I'm no expert on the manifold issue but I've read that the temps can vary quite a bit. I am guessing that if you can get one of those point and shoot thermometers and post a temp for both sides. Someone on here can tell you if that is an acceptable range. I'm guessing they should be under 140 but not sure.  You can go into your profile and change your user name. Also there is a link on the left to my discussions. Which should help you find your threads. 

girls2water

Well recently I found that I had a lot of barnacle coverage on the outdrive and scraped that off.  Still have my exhaust manifold on the left getting hotter then it used to in the beginning of the season.  Also seem to have thick exhaust when it first starts up BUT I think after reading that maybe I also have a starter cellinoid issue bcause when I turn key nothing nothing and then all of a sudden it starts right up.  I thought I wasn't starting it properly (first turn is alarm tester) but now thinking starter c.  Sheesh time to really learn about this engine.  Would the exhaust be thick because several turns before the start?  too much fuel - yes the blower is on and I am now opening the hatch due to safety concerns! 

aero3113

If it is black exhaust smoke then it's a fuel issue, you could be flooding the engine.

girls2water

I discovered that my impeller is failed, Could that have been the noise I heard?  Now now I am interested in the best order of action to determine how much damage could have been done due to failed impeller.  I have seen many discussions on how bad this can be but what is the order of checking.  The last run of the year did seem to give a carburetor popping and loss of power.  Is my engine gone? Any step by step guidance to make sure I don't get ripped off would be helpful.  Thanks.

clarkbar

When I had water in my fuel, my boat made load back fire popping noise. Check your fuel filter. 

212rowboat

Try not to diagnose fuel issues by exhaust or exhaust remnents without a wide band o2 sensor... Reason: black residue demonstrates super rich air to fuel ratio, which would lead a reasonable person to believe means the engine is running rich- and it is, but... 

You may have one cylinder or bank of cylinders running very lean, and the other side attmepting to compensate by running super rich.. leaving the black stuff, and leading you to trim fuel out of an engine that is already lean on one bank/cylinder.. you don't wanna know what happens when you do that.  

So.. pull your plugs and compare the business end of them against a chart... It'll tell you rich, lean, predetonation from too advanced timing or or retarded.. check your fuel rail pressure.. momentary loss of fuel pressure during acceleration can drop pressure until it catches up, and lean causes backfiring.. 

Lean is hotter than rich.. a lean bank, which is why one riser is hotter, can be obstruction in the fuel supply lines going to that bank, a vacuum leak on that sides runner, or something similar.  

CrewLounge

Change the spark plugs

dbomb

girls2water said:

I discovered that my impeller is failed, Could that have been the noise I heard?  Now now I am interested in the best order of action to determine how much damage could have been done due to failed impeller.  I have seen many discussions on how bad this can be but what is the order of checking.  The last run of the year did seem to give a carburetor popping and loss of power.  Is my engine gone? Any step by step guidance to make sure I don't get ripped off would be helpful.  Thanks.

Pull all the water lines off the motor and you MUST find all the pieces of the impeller. Put them back together like a puzzle.