Mercruiser 3.0 litre bogs ONLY on first accelleration of the day

[Boatsoleil]

I have a little Sea Ray 175 SRX (2003) with a 3.0 litre Mercruiser sterndrive (Engine serial number OM634774). Two years ago I was having starting problems, and the marina where I had it serviced rebuilt the carburetor. (Carb has numbers etched on body: 864940 21 2Z23). That fixed the starting problem, but the next season a new issue appeared. After starting the boat from cold, and letting it warm up and then navigating at idle speed out of the marina, when I push the throttle forward to accelerate, the boat bogs. If I pump the throttle it recovers and accelerates. Then it is fine for the rest of the day: I can accelerate from idle and it does not bog. Even after shutting the engine off and letting it sit for an hour or two, when I re-start it then push the throttle to accelerate, it does not bog. The problem only happens on the very first acceleration of the day. I no longer live near the marina that rebuilt the carb, so before bringing the boat to a new mechanic I was hoping to get some advice on what might be the cause. F.Y.I. the boat got new plugs, wires and distributor cap about 4 years ago. Also, the boat often sits 2 weeks between uses. Thanks for any ideas anyone might offer.

 

[alldodge]

Sounds like your choke just needs adjusting. When the motor is cold the choke is used to supply more fuel. When the choke opens fully the extra full stops. Could be it needs a bit more time in the partial closed position.

 

[alldodge]

sorry wrong thread

 

[Boatsoleil]

Thanks AllDodge.

Re: your post: "Sounds like your choke just needs adjusting. When the motor is cold the choke is used to supply more fuel. When the choke opens fully the extra full stops. Could be it needs a bit more time in the partial closed position."

I did notice that when this happens the choke butterfly is fully open. But the engine is already at operating temperature bu the time I get out in the channel and push the throttle to get up on plane. Shouldn't the choke be fully open by the time the engine has reached operating temperature? Also, the choke spring/coil seems a little rusty. Do these things (spring/coils) ever need to be replaced?

 

[alldodge]

Looks like one of my post would up on your thread

If your up to operating temps then the choke should be fully open, if its not that might be the issue

 

[SeaDooSam]

To me, it sounds as if there is some dirt or something bad in the gas. When it sits in the carb for a little while, the dirt may gum things up. This would cause the engine to not want to accelerate at first. Since it only happens on the first acceleration, that gunk is probably blown through and it will work fine after that. This would be my guess. Maybe try some gas treatment. I like Starbrite (blue bottle).

 

[Boatsoleil]

Hi SeeDooSam. No. This wasn't just a one-time occurrence. It happens every time I use the boat. And I'm quite particular about the gas. Always use premium non-ethenol blend. Put Sta-Bil marine formula in every tank. And before first start of the season I drain the on-board tank (check for any water or phase separation) and put in fresh. Don't think it's the gas. Thanks for the input, though.