rough idle on 3.0L mercruiser?

[Super_Dave]

I just purchased a 2000 Sea Ray 180BR. It has the 4banger Mercruiser 135hp with an alpha-1 lower unit(?). Only 133 hours. Owner seemed to take very good care of it. He winterized it every year, kept it clean, etc.<br /><br />I just took it to the lake for the first time (other than my test ride). It seemed to run pretty rough at idle, but silky smooth on throttle. Is this normal? Until it got warm (~170*) it would literally shake. It idles at about 800rpms (is this low)<br /><br />Also, going into gear from neutral, it sounds kinda harsh. You can hear the gears meshing/clunking. The seller said you don't want to go into gear slowly, and going into gear quicker seemed to help a lot.<br /><br />This is my first boat so I'm not sure if this is normal, just needs a tweak or what.

 

[richard99]

Re: rough idle on 3.0L mercruiser?

Dave - the shifting thing is normal. If i'm not mistaken, moving into either gear is also assisted by a momentary engine cut-off switch to lessen the gear-grinding.<br />Regarding the engine performance, I would replace all the ignition components (points, plugs, wires, cap and rotor especially)if it hasn't been done already. Good luck

 

[MainstreetUSA1]

Re: rough idle on 3.0L mercruiser?

The Alpha-1 has what is called a "dog clutch" to engage forward and reverse gears. It's best to move the gear shifter into and out of gear "swiftly". This will minimize the gear grinding noise.

 

[Super_Dave]

Re: rough idle on 3.0L mercruiser?

ahh, thanks guys. Dog cut gears would definately explain the shifting noise. At least now I don't have to worry about wearing out synchros!<br /><br />I'll look into the ign tune up... just gotta figure out what "points" are.

 

[vipzach]

Re: rough idle on 3.0L mercruiser?

If you have a year 2000 boat, you probly don't have points, just a dist cap and rotor.

 

[texsun]

Re: rough idle on 3.0L mercruiser?

Dave,<br />Upgrade to Mid Grade fuel and run a couple of tanks thru it. I believe some people on this forum have indicated that the 3.0 is not the smoothest idling engine. Sounds like the prior owner gave you the right info about shifting.<br /><br />If ya just got it I'd watch the temp gauge real close and run a couple of tanks thru.<br /><br />Mark

 

[texsun]

Re: rough idle on 3.0L mercruiser?

Dave,<br />About the temp gauge. 170 sounds just right. Do you know if the prior owner ever replaced the impeller for the sea water pump? The 133 hrs you spoke of is about the time a average boater (40-50hrs/yr) might see a failure if no impeller replacement has been done. It will be well worth your time to find out and to get it replaced rightaway if it's never been done.<br />Mark

 

[Northern Eclipse]

Re: rough idle on 3.0L mercruiser?

Just to add the the above advise, I suggest also that you have the drive leg pulled and inspect and service engine coupler ( requires some grease) u-joints and gimble bearing and inspect or replace u-joint and shift cable bellows.. and yes the 3.0 is known to idle a little bit rough.

 

[Super_Dave]

Re: rough idle on 3.0L mercruiser?

Thanks for all the replies guys. I'll be checking into the impeller. My neighbor (who has been boating his whole life) also told me the impeller should be replaced about every 100 hours.

 

[Super_Dave]

Re: rough idle on 3.0L mercruiser?

Also, does 800 sound right for an idle speed. I was thinking bumping it up to 900 might smooth things out.

 

[Bondo]

Re: rough idle on 3.0L mercruiser?

Originally posted by Super_Dave:<br /> Also, does 800 sound right for an idle speed. I was thinking bumping it up to 900 might smooth things out.

No,.........<br /><br />650rpms is the # you're looking for..........Your Already Too Fast.........<br /><br />I think you've got Issues with the Idle circuit of your Carb........<br />It should Idle at 650rpms, rather Smoothly.........

 

[Mile-High Mariner]

Re: rough idle on 3.0L mercruiser?

Dave - you do NOT have points or a condenser in your 2000 Mercruiser ignition system. Merc used several different types of electronic ignitions in the 3.0 and other power packages; out little 4-cylinder motors were equipped with either the EST (electronic spark timing), DDIS (digital distributorless ignition system) or the Thunderbolt IV. Most common seems to be the EST, in which case you'll want to look into the ignition module along with the other ignition items. It's attached to the distributor with two screws and connected to the ignition system via three connectors, two from the outside and one on the inside of the distributor. Take the ignition module out and have it tested - you local Autozone or other auto parts shop should have the equipment to test this standard GM module. It's pretty easy to tell if it's gone bad, though - you'll either get no spark or no timing advance.

 

[olbuddyjack]

Re: rough idle on 3.0L mercruiser?

Originally posted by Super_Dave:<br /> just gotta figure out what "points" are.

Kids...