engine bogs under load

[1999 Searay 180BR]

I have a 1999 SeaRay 180 Bowrider with a 3.0L Mercruiser. I didn't get to run it last summer so it has been sitting awhile. The engine would crank and idle but would not take the gas when the throttle was advanced.I assumed bad gas or gummy carb so I siphoned the tank dry and filled with fresh gas (93 octane),removed carb, disassembled and soaked in ChemTool carb cleaner for 2 days, installed new complete carb kit, inspected fuel pump filter( looks good ), reassembled everything. It cranks and idles fine. It will even taxi fine, but when the throttle is advanced it bogs. The engine never dies it just won't open up. In neutral with high idle it will rev off the scale, but in gear WOT = about 2000rpm maybe a little more...any ideas?

 

[Don S]

Re: engine bogs under load

Did you install a rebuild kit in the carb? did you set all the adjustments per the manual? did you blow all the passages in the carb out with compressed air?<br />How about the fuel filters? were they changed and checked for water. <br />When was the last time the engine had a complete tuneup. Cap, rotor, plugs, cleaned flame arrestor, all sorts of neat things.<br />Do you have a Mercruiser OEM service manual?

 

[Bondo]

Re: engine bogs under load

Ayuh,....<br />Was there a New Accelerator Pump included with the Carb Kit,.??....<br /><br />It Either needs Replacing,.. Or Adjusting......

 

[1999 Searay 180BR]

Re: engine bogs under load

yes rebuild kit was installed and yes it included the accelerator pump, both filters look good, gas is new 93 octane, new plugs, carb is as clean as it was the day I bought it...maybe cleaner. I am almost convinced its not a fuel related problem...maybe distributer, but I'm leaning toward this thing I've read about called an exhaust flapper. I didn't know this even existed much less where it is located but from what I read people with flapper problems had the same symptoms I'm having. Any insight on this topic?

 

[Bondo]

Re: engine bogs under load

The Flapper resides in the Downpipe,..... Just Below the Riser......

 

[searay3]

Re: engine bogs under load

Part of the tuneup process includes the distributor. Once you have the rotor off, check the weights for the advance. Maybe rusty/sticky..not advancing.

 

[1999 Searay 180BR]

Re: engine bogs under load

I'm gonna check the distributer first thing in the AM since it is easier to get to...as for this flapper thing, what's the best way to get to it to check it and please don't say pull the motor!!!

 

[JoJoBetsy]

Re: engine bogs under load

I think you've elliminated any exhaust flapper malfunction by getting rpm in neutral. What would make the flapper work in neutral and not in gear? There's no connections to it; it just resides in the downpipe I believe. Also, and not as any kind of technical expert, I believe getting rpm in neutral is different than getting rpm when the engine is under a load.<br /><br />This sounds like an ignition advance or fuel restriction problem. Do yourself a big favor and get a Merc service manual. The troubleshooting section covers this very problem in detail and I don't remember seeing anything about checking a flapper valve in the exhaust route.<br /><br />Wish I could help more. jb

 

[Don S]

Re: engine bogs under load

I think you've elliminated any exhaust flapper malfunction by getting rpm in neutral.

Not really, you could have the exhaust nearly blocked off and still get 6000 rpm out of the engine in neutral with no problem. There is a larger volume of air going in and out of an engine under load than when in neutral.

 

[JoJoBetsy]

Re: engine bogs under load

That makes sense, thanks for the correction.

 

[fishnfiend]

Re: engine bogs under load

Float adjustment in carb makes a difference on these motors. Too low fuel level in bowl - won't activate secondary circuit soon enough - results in bog. Search "bog" on this forum - I think a member named Ron (ron7000 ??) described his solution with an identical problem.<br /><br />I have an '86, same motor. Have raised float level some, but not quite enough. 75% of my bog is gone. Apparently takes some trial and error - the correct final setting was higher than recommended by Merc.<br /><br />OOPs just reread your post. I could get to WOT on mine, just had to do it very gradually (or would get bog). The fact that you can't get over 2000 probably means different (or additional) problem. Good luck (I'll watch this thread with interest).

 

[1999 Searay 180BR]

Re: engine bogs under load

I may have found the problem..contacts in the distributer cap corroded( really bad )if I knew how to post pics I would show ya. I cleaned the contacts with electrical contact cleaner and emery cloth until smooth. I ran it on the flusher and it sounds normal again ( purring )I'm gonna take it to the lake later this evening to see if it will open up...I'll let ya know. Thanks to all for the suggestions, you may have saved my holiday weekend!!

 

[csanna2]

Re: engine bogs under load

Dont forget to check and make sure your outdrive isnt binding up. Sounds like the problem Is when Its in gear. Right! Runs fine till Its in gear.

 

[1999 Searay 180BR]

Re: engine bogs under load

same problem, looks like the weekend may be lost.I have not checked the anti-siphon valve. Could this cause it to bog under a load but, rev fine in neutral? Is there any way to check the coil? Seems to me if the coil was bad it would bog all the time.

 

[Don S]

Re: engine bogs under load

If you had one cylinder that had absolutely no compression, it would still run up to high rpm in neutral. Reving high in neutral is a non test and means nothing.<br /><br />Here is a list of items known to cause low rpms under load. Start eliminating and you will find the problem.<br /><br />