HELP!!!! Mercruiser bogs out at 30 mph

[chesire]

I have a 1986 3.0 mercruiser i/o with a Mer 2bbl carb she runs like a champ until I get to 30 MPH I am not sure if it always at the same RPM or not. Ican open it up and it will get up and go no problem. but once it gets to 29 30 -sputter sputter cough cough- than i have to back down AND CAN CRUISE AT 25 ALL DAY NP. I replaced both fuel filters hoses I dont have a vent problem. I then replaced the anti- syphon valve with just a plain fitting Took it out twice and she ran great!!!! after about 6 hours of use it started again. In the past it has also come and gone. I have seen Many Many posts of people that have rebuilt carb and replaced fuel pumps to no avail. Unfortantely they stop posting after they get their fix Some one please help!!!!!! I dont think it is flooding out IO dont smell gas and if i shut it off it starts right back up. Also doesnt help if I squeeze bulb.am at whits end errrrrrrrrrrrr Ready to make an artifical Glastron reef. Thanks<br /><br />

 

[trevorcday]

Re: HELP!!!! Mercruiser bogs out at 30 mph

These problems are almost always fixed by rebuilding the carb. It is really easy on the 3.0L motor. Buy a rebuild kit, take the carb off, disassemble and clean everything, then put it back together. I have found a lot of these carbs have corrosin in the float bowl. The crusty white stuff that comes off the casting when it corrodes gets into the jets and makes the motor run poorly at full load steady speed.<br /><br />Good luck.

 

[Trent]

Re: HELP!!!! Mercruiser bogs out at 30 mph

Go to Wal Mart and buy some Berrymans B12 in a can and dump it into the fuel tank..Very good stuff!! Iv used it for years..<br /><br />This would be the first thing I would do.<br /><br />Check the compression and the timing also. Do you still have points system installed on this? For around 75.00 you can install electronic ignition on this engine. <br /><br />You could also check the timing advance at wot.

 

[johnkc]

Re: HELP!!!! Mercruiser bogs out at 30 mph

chesire , have you taken a fuel pressure test at this speed{tee fitting}also are you sure the fuel filter in the carb is installed with the solid end towards the carb,with the spring in the carb first?i find the filter in back wards on occasion.and it causes a problem like this

 

[chesire]

Re: HELP!!!! Mercruiser bogs out at 30 mph

I have not checked the fuel pressure at wot or at all for that matter. don't know how to but ill look into it. (being a boat owner is very educational) I was gonna clean out carb with marvell mystery oil/gas today but my dumb ass started the boat with garden hose at just above a drip today so i guess ill be replacing impeller next. I want to check timing advance next. can some one tell me how? errrrrrrrrrrrr it was 85 again today and I'm stuck on land. thanks for the help guys also if it was the timing advance wouldn't i be flooding? (assuming i don't also have a fuel problem) also ill check the plugs tomorrow what should i look for (what colors for what) thanks bill

 

[petryshyn]

Re: HELP!!!! Mercruiser bogs out at 30 mph

If thats a rochester clone, johnkc is on to something. The fuel filter may be in backwards, but most likely just plugged. It will bypass fuel when plugged, but won't allow full flow.....causing high speed bog. There may also be a power piston stuck in its bore (inside carb's top cover). This will cause hesitation and lean at high speed. <br />>check filter first

 

[chesire]

Re: HELP!!!! Mercruiser bogs out at 30 mph

ok I pulled the dist cap and cleaned every thing with contact cleaner (what a mess) I think that the cap was on wrong, in that the slot and the place for the slot weren't lined up would that effect it? I haven't had a chance to run it in the water yet. I did check fuel filter it was ok (i even ran w/out filter before) <br />now i have a question for ya may sound dumb but.... I have noticed oil around my carb I think it is coming from the hose that runs from the valve cover to the flame arrrestor A small puddle Is this Normal?

 

[chesire]

Re: HELP!!!! Mercruiser bogs out at 30 mph

OK so i pulled the flame arrestor and cleaned it it was filthy Duh!!! I know this could be the problem or at least part of the problem with the bogging down but what about the oil? also pulled plugs and they were black too.

 

[Fouled Plug]

Re: HELP!!!! Mercruiser bogs out at 30 mph

Chesire, the plugged arrestor wasn't doing you any favors. Neither was the misaligned distributor cap! May have been running rich from the dirty air intake and fouling the plugs. Clean and gap 'em and see what happens. The oil is from the crankcase breather, so a small amount is no big deal. Set the timing, adjust the carb, and let us know how she goes.

 

[chesire]

Re: HELP!!!! Mercruiser bogs out at 30 mph

OK here is where I am... The lower unit is pulled and in my garage (see earlier posts) I am getting ready to istall water pump. inside the lower unit is some corrosion I scraped some free with am screw driverand sucked out with shop vac what I want to know is can I spray cleaner ond hose out with water(like carb cleaner) w/o doing damage. what about anti-fouling paint? hope to be on the water tomorrow thanks