Mercury 175 EFI low end bog

[mhines]

1999 merc 175 EFI s/n: OG870939...I've had the motor for the past 10 years. Boat doesn't get used as much in the last 5 years as it used to...took the boat out tonight, and it has NO low end power, and at idle sounds like it's full of marbles. Coming out of the hole, it sits at 3000rpms and I have to zig zag the boat to get it to break over.....once on plane it runs out to 5200 or so Rpms, and 60+mph. At higher Rpms it sounds smooth and normal.

It used to jump right out of the hole just fine. Also the rattle or knocking sound at lower Rpms never used to be there...


Any ideas?


Thanks

Mike

[TMANN]

Always start with the basics. Fuel, spark, compression, read the plugs. Don't run it at high rpm till you figure it out. Doing so is a good way to junk a powerhead.

[mhines]

plugs are brand new...old ones looked good.......I would THINK if it was a fuel issue, i would have problems at high rpms, as well as low rpms...its strange to me, that at idle it sounds terrible, but above 4000 rpms or so, it seems strong, and runs great!

[EuropeanAM]

Drop gearcase and check up in the midsection to verify that the exhaust tuner is secured to the bottom of the adapter plate....

[mhines]

Drop gearcase and check up in the midsection to verify that the exhaust tuner is secured to the bottom of the adapter plate....

I think you might be on to something, as I had a feeling it might be exhaust related.


If it's not secured, what's the fix?

[EuropeanAM]

Pull powerhead and adapter plate, extract any broken hardware, inspect for damage components, and reassemble using Stainless BOLTS, washers and red liquid loctite (get rid of the studs and nylock nuts).