Bad idling, jerky ride at slow speed

[rizy1976]

Hi guys. Follow up to my previous posts. Had bought a 1988 boat which was not used since 1995. Had bad engine noise. Fixed the issue by replacing the rod and bearing. Now motor sounds great but does not idle. Bad gas in tank.<br />Filled up 14 gallons of gas on top of the old gas and took it to water. Had to keep pumping gas to keep the motor running. Run really bad when put to gear in slow speads. It jerks off and its ugle to see it jerking with tilt nose up and splashing water on the back as it jerks fast enough. <br />Once in deep and trim down boat runs really good. Touched 50mph the this weekend. <br />Needs cleaning of fuel system? Where to start? No such experience from fast. Fuel filter need repalaced. User manual says something about a filter in carborator, does that need to be replaced? How to clean carborator itself without messing up the setting? Help wanted. thanks

 

[Gary H NC]

Re: Bad idling, jerky ride at slow speed

What kind of engine?<br />Does it have a fuel-water seperator?<br />Sounds like you had gas in it that was 11 years old? mixing fresh gas will not help fuel that old.<br />there is a small filter in most carbs where the fuel line attaches on the body of the carb.<br />If it was mine i would change the filters and drain all the gas and try again..

 

[bamadave]

Re: Bad idling, jerky ride at slow speed

Rox, we need more info on the engine.

 

[Mile-High Mariner]

Re: Bad idling, jerky ride at slow speed

What you guys need is to learn how to spell. <br /><br />Rox - I agree with Gary (and not because we're both from North Carolina!) - a good fuel/water separator is in order. Your current problem is likely a result of 11 years worth of condensation accumulating in the gas that sat in the tank all that time. I would definitely drain the tank completely (major PITA) and try to do it in such a way as to vacuum up the crap from the bottom of the tank while you're doing it. You might have to empty it, add some fresh gas and pump that out, repeating until your tank is clean.<br /><br />You indicate that the motor runs well at speed - the poor performance at low rpm and the improvement at higher rpm points to a possible carburetor issue (your idle/low speed circuit may be all funked up from sitting for so long, while the high-speed circuit isn't as badly gummed); I would strongly recommend rebuilding the carb, especially considering it sat for SOOO long, with no indication that the fuel was treated with an adequate stabilizer prior to its last storage. The fact that it stays running when you pump it tells you that your accelerator pump is working at least nominally, so that's a good thing!<br /><br />Rebild yur carburater, get the wator out of yur tank, and install a wator-seperating filtor. <br /><br />Oh, and make sure you've been diligent with the oil change and drive unit maintenance, too. These engines are pretty sturdily built, and you just have to stay on top of the maintenance to enjoy years (or thousands of hours) or reliable fun.

 

[rizy1976]

Re: Bad idling, jerky ride at slow speed

thanks guys for replying. Sorry for not giving info on my boat. <br /><br />1988 Bayliner <br />OMC Cobra 5.7<br /><br />I agree with you guys and I would need help on these procedures. <br /><br />1- What would be the best way to drain the tank? would simple siphon work here?<br /><br />2- How hard it is to rebuild the carb? How would I go about it. Are these carb rebuild kits are "do it yourself" types? Which kit would I need?<br /><br />3- What would be the best way pump some oil from tank ive noticed it way higher than full level.<br /><br />Thanks in anticipation.

 

[Gary H NC]

Re: Bad idling, jerky ride at slow speed

MILE HIGH,What did we spell wrong? <br />Just pikin on ya MileHigh..

 

[Gary H NC]

Re: Bad idling, jerky ride at slow speed

Rox,On my fuel tank i have an access in the floor,i removed it then pulled the fuel guage sending unit.That give me a good opening right at the rear of the tank. I used a hand pump and a gallon jug..takes awhile but i got it all out and could see the bottom of the tank.<br />How high is your oil level? <br />I would change the oil and filter to check for water in the oil if it was way over full.

 

[rizy1976]

Re: Bad idling, jerky ride at slow speed

Well, Ill try to use a hand pump to suck the gas out not sure about the access in the floor ill check it today.<br /><br />About oil level actually my mechanic worked on the motor to change bearing and rod coz the engine was making grinding noise when i first started it. That prob is gone but I think he filled the oil way too high. He says its file but it bothers me to have 1" over the full mark. <br /><br />I think a pump would do that also. Where sould I suck the gas and oil from (what outlet).<br />Thanks

 

[rizy1976]

Re: Bad idling, jerky ride at slow speed

Please give me some suggestions on how to rebuild a carb? I just bought a service manual for my boat and would want to do it myself.

 

[Gary H NC]

Re: Bad idling, jerky ride at slow speed

one inch over the full mark sounds like about a quart too much.You could use a pump for the oil too,they make one that goes down the dipstick tube. <br />look at this one...cheap enough..<br /> http://www.yachtsee.com/pelaoilextractor6000.htm <br /><br />Is the carb a 4 barrel? What kind of carb?

 

[scottatwork]

Re: Bad idling, jerky ride at slow speed

I had this same problem but at top speed it finally started carb backfiring.<br /><br />Put the water fuel separator in and so far runs good.....too much gas for me to drain out of mine so I gotta do it the hard way

 

[rizy1976]

Re: Bad idling, jerky ride at slow speed

Boat has 4 Bbl Rochester Carb. Ill try out with the pump. <br /> http://www.iboats.com/mall/index.cg...1149103392&search_in_category=f&view_id=41558 <br /><br />Please help me out with Carb rebuild project I really want to do that. It looked dirty when I opened from top backfire arrester.<br /><br />Scott, give me more info about water fuel seperator I might as well put that on too. Which one would I need and where does it sit in fuel line. Any help for installation?<br />Thanks guys.

 

[Mile-High Mariner]

Re: Bad idling, jerky ride at slow speed

Rox:<br /><br />Just about any marine parts source (iboats is one) will have the correct carburetor rebuild kit for your application. It'll have everything you need to do the rebuild, except maybe the float - but your service manual will tell you how to check your float to see if it's okay. It may not need replacement, so check it out. <br /><br />I hope you have at least the Seloc manual - the Clymer is not a favorite of many on this forum, and if you sweet talk Don S, he may provide you with a link to the authentic, original OMC manual, if he has the link. I know he's posted the links to the Mercuiser ServMan, so search the forum for your manual. Otherwise, the one you have should have adequate carb info for your purposes (tear-down and rebuild, etc.).<br /><br />If you're going to do a good job with the fuel tank, make sure you have a pump or suction device that will generate strong suction; a simple siphon will definitely not suffice there.<br /><br />Gary - it's fun to pick on each others' foibles here, as long as everyone knows it's all in fun! I was born and raised in N.C. - Asheville to Washington-Wilmington points Piedmont, and most of my relatives still live in Pitt County. I try to pick on everybody I see from N.C., just to feel close to home!

 

[Mile-High Mariner]

Re: Bad idling, jerky ride at slow speed

Oh, yeah - Rox: if you want to do like Scott and get your gas out the hard way, just add a can of SeaFoam to your fuel tank and spend all day (or, with the rate at which your OMC 350 V8 burns gas, a few hours) running it around the lake to burn out the gas. The SeaFoam may actually improve your carb's function by dissolving away some of the gunk that's built up in the passages, but you will STILL need to tear it down and rebuild it. There's no way around that one, pal, after the poor thing sat, unloved and neglected, for so long.

 

[Mile-High Mariner]

Re: Bad idling, jerky ride at slow speed

Sorry, Rox - I just saw your post about what your mechanic said about the oil being "fine" overfilled. Overfilling the sump is not "fine"; it can cause cavitation (crankshaft hits the too-high surface of the oil pool), which will froth and foam the oil and result in poor delivery to the lubricated engine parts, same as if your oil level was too LOW. Suck or drain out the amount necessary to give you the proper level on your dipstick, but make sure to check the oil level with the boat in the water, or at least at the same trailer angle as if it were in the water.

 

[rizy1976]

Re: Bad idling, jerky ride at slow speed

Hi guys, Thanks for suggestions.<br />I plan to work on my boat today but at the same time preparing to do a carb job. Please advise what kit would I need. I think this is what would work on my carb.<br /><br /> http://www.iboats.com/mall/index.cg...1149179457&search_in_category=f&view_id=45197 <br /><br />And this is the carb that I have in my system.<br /><br /> http://www.iboats.com/mall/index.cg...1149179749&search_in_category=f&view_id=41558 <br /><br />The kit seems to be generic for 4 Barrel carb so just wanted to make sure it works on my carb.<br />Thanks

 

[rizy1976]

Re: Bad idling, jerky ride at slow speed

Hi guys.. latest update... I tried to easy way before heading on to the big one... Cleaned carb from outside.. washed backfire arrester with a solvent as it was completly chocked... added one can of SeaFoam in the tank.. started it found it much better.. but engine runs too rich.. idles at 1500 at first and comes down to 1200 when after warm up. <br />Seems like I can not get away without a carb rebuild...

 

[Mile-High Mariner]

Re: Bad idling, jerky ride at slow speed

Rox: your high idle speed has less to do with the mixture than with the idle speed being set too high - it requires a simple adjustment to bring down your idle speed. Adjust it according to the service manual instructions, found here: http://www.boatfix.com/merc/Servmanl/13/13B5R2.PDF <br /><br />Make sure your check and adjust your settings with the outdrive in the water (no water collar) and in gear.