2.5L omc sluggish

[dschuma72]

Hello, <br /><br />I'm not too skilled with motors but want to try and cure this myself. I have a 2.5L omc that misses bad and sputters until it hits about 3200rpm then it all of a sudden acts like it snaps out of it and takes off with less missing and hesitation.<br /><br />There's a slot in the crankshaft pully that I assume would be top dead center correct? I make a mark on that slot and use a timing light to set the timing at -4 BTDC which is what I'm supposed to be at when my tach reads 700rpm correct? Ok, I did all this and it runs like total crap. I set the timing by ear and it runs much better than being set with a timing light but it acts like I described earlier. Will chug til I get about 3200rpm and then act as to pull out of the sluggishness and take off like it should.<br /><br />Any help is appreciated.<br /><br /><br />Thanks

 

[Boatist]

Re: 2.5L omc sluggish

Your timing marks will be on the harmonic blancer not the crank.

 

[Bondo]

Re: 2.5L omc sluggish

And, My Guess is,<br />Your Running Issues are Fuel/Carb related........

 

[dschuma72]

Re: 2.5L omc sluggish

Had the boat out today and right before brining it in to the dock I decided to mess with it a little more and pulled plug wires as it was going. I pulled the #2 cylinder wire and nothing changed. All other 3 wires when pulled made the motor miss even more like it should but #2 being pulled didn't change a thing. <br /><br />I then swapped the #1 and #2 plug wire and it was still as if #2 wasn't firing and making the motor miss so that ruled out the wires being bad I assumed. I then pulled the distributor cap and looked at it and the pulled the rotor off and checked that also, slightly corroded and will be replace but I just planned to put it back together and mess with it more on the muffs. <br />I didn't change a thing, all I did was unscrew the cap and pull the rotor off and now I have no spark at all coming from the coil. Boat left me stranded and wouldn't start. I have about 4.5v going to the coil when I turn the key on but my spark checker gets nothing when the engine is being cranked and connected to the coil wire. Thing just lost all spark. <br /><br />Any ideas what my prob is now?<br /><br />The second time I popped the cap off the distributor I noticed that the little black wire coming in the distributor pulled out of seat real easy but I unscrewed the mounting screw and snugged that wire down pretty tight and there still no spark coming from my coil.<br /><br />Any help is greatly appreciated.<br /><br /><br />Lesson learned today... always pull upstream of the dock when you plan to work on your boat as the current sure be tough with one ore if she leave you stranded. heh

 

[Boatist]

Re: 2.5L omc sluggish

Well it sounds like you have a problem with the #2 cylinder and now a second problem. You don't say what year so I will assume this is a standard points and condenser distributor. The distributor is pretty simple, really just a timed ground that causes the coil to fire then a rotor to direct to the right cylinder. You say you have about 4.5 volts to the coil but do not say where you messured. The plus side of the coil while cranking should be what ever the battery voltage is at that time( 10 or 11 volts). The points plate must have a ground wire on it to the block. Points should open to about .018 inches on top of the lobe. Wire from the points goes to the minus side of the coil. With or without the Cap and rotor on you should get spark out of the coil. If you get good spark out of the top of the coil then put the rotor on make sure the top spring is not broke off and that the rotor and cap are seated in there alignment notch.<br /><br />If you got no spark out of the coil then check the coil. Take the points wire off the minus side of the coil. Jumper 12 volts to the plus side of coil and with a another jumper wire to ground tap the minus side of the coil. each time the coil should fire. May not be as hot a spark since the conderser is not hooked up. If the coil works then hook up the points wire fron the distributor, make sure the points open as the motor turns. Run a peice of paper thru the points to clean or clean with 400 sand paper. With the points hooked up and the condenser every time the points open the coil should fire. Again while cranking the + side of the coil should be battery voltage (10 or 11 volts)<br /><br />After you get the coil and distributor fireing then time to take a compression check on the # 2 cylinder and find out what wrong there.

 

[dschuma72]

Re: 2.5L omc sluggish

Boatist, you a good man and I appreciate your taking the time to instruct me on what to do. This info is going to help me a lot on figuring out what's wrong. <br /><br />If you have any computer issues or such give me a shout and I'll help hook you up with the repair.<br /><br />Thanks again, with that info I don't see why I can't figure out the scoop.<br /><br />I appreciate it!

 

[dschuma72]

Re: 2.5L omc sluggish

I changed the points, coil, plugs and she fired up and runs much smoother now.<br /><br />It still runs a little rough at low idle and only hits about 4000rpm WOT when the timing is set to 4BTDC. Is a 2.5l OMC supposed to be set at 4deg BTDC at 600rpm?<br /><br />I have a little issue with not even knowing 100% that this motor is a 2.5l and I'll fill you in on the story. Grab your coffee or beer as I may get windy...<br /><br />I bought the boat last summer and it's a 1987 Bayliner Capri 19'. Supposed to have a 3.0L in it but the guy I bought it from said they put a remanufactured 2.3L in it. The motor has GM stamped on the block so it can't be a 2.3L as 2.3L is Ford. Today I went to get points for it and two different places gave me the same points that were for a 2.5l but they didn't fit or match my current points. I ended up taking the old ones in and they paird them up by physical appearance.<br /><br />Anyone have an idea as to how I can tell exactly what motor this is? It looks identical to the pics and service manual to the 2.5/3.0L<br /><br />One more thing I could use a little info on is the rochester 2jet carb on it. I was under the assumption that the two needle screws were to be screwed in just snug then backed off two and a quarter turns. I do that and it seems to run a little rougher at low idle but when I screw them in a little tighter it smothes out slightly. What should they be set at?<br /><br />Thanks!

 

[Boatist]

Re: 2.5L omc sluggish

One difference you can see is in the exhaust manifold. The 3.0L input water hose comes in on the starboard side of the thermostat houseing. The output water goes out the Port side of the thermostat houseing to the exhaust manifold.<br /><br />The 2.5L input water comes in thru the exhaust manifold and output goes out thru the exhaust manifold, so the front of the exhaust manifold has two hoses on it. The 3.0L only has one hose on it.<br /><br />Do a compression check on your engine. Low speed miss very likely a valve problem on the weak cylinder. Valve problems will show up as a low speed miss and smooth out as the rpms go up. Should have 130 psi or more.<br /><br />Thanks for the kind words but computer systems, PC and printers is what I have repaired for over 30 years.

 

[ILIKEROSTERTAILS]

Re: 2.5L omc sluggish

Hi,<br />I have a 2bbl Rochester on my 3.0 OMC the "needle screws" are suppose to be screwed all the way in, then start the motor and warm it up, once it is warm screw them out equaly till the motor stumbles a little then in till you get the highest and smoothest idle. Next if you have an automatic choke turn the adjuster on the front of the carb left till the choke is closed and then slowly right till it just starts to open. After that you carb should be tuned. Also the motor should idle between like 650 and 850 RPMs<br />Good Luck,<br />Ben Hunter