1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

[NikeR6]

Hello all, what a great site, have been searching hi and low!! I have found some great tips for the problem I am experiencing, but would appreciate a few more! New to boating, have a 1984 Citation with an OMC 120 2.5 Litre Sterndrive. Model # 252STHRCRA Drive unit model # 988486. Like the title says, boat starts up great, idles great, cruises great, full throttle, half throttle etc, and then all of a sudden like someone is turning the key off it just stops and will not start again until I get towed back to shore then trailer it home! No sputtering or anything, just an abrubt stop. Thought fuel related maybe, changed fuel lines, filters. After changing lines and checking the little ball valve thingy, starts up runs great again for 20 minutes then dies and I get another tow in. Saw somewhere on here about a bad coil maybe. Got a new one. Same thing, 23 minutes of great running, then dead in the water. Temperature guage seems to work, it gets hotter as boats not moving much, once I go it cools down, but the last time it died the water hoses were all too hot to touch.... I had taken the bigger water hose off while it was running in the driveway for 2 seconds to check the flow and there was water coming out. Maybe not enough? Maybe a bad thermostat? Impeller gone bad? I guess the temp guage could be wrong? I am going to change the points and condenser in the distributor I guess as I saw this stated in another thread.. Any help is greatly appreciated.. Kids were so sad after we got towed in that they made me pull over in the truck as we were heading home to have our picnic in the boat in a little pullout on the side of the road!

 

[RogersJetboat454]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

Welcome to Iboats.

Sounds like you need to spend a little diagnostic time on the boat before throwing down more money on guessing.

How hot is hot (what's your gauge saying)?
If you haven't replaced the impeller recently, it's time to do so. They are typically replaced every 2-3 years.

Have you checked for spark when the engine peters out on the water?
Can you duplicate the same problem on the trailer?

 

[NikeR6]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

Welcome to Iboats.

Sounds like you need to spend a little diagnostic time on the boat before throwing down more money on guessing.

How hot is hot (what's your gauge saying)?
If you haven't replaced the impeller recently, it's time to do so. They are typically replaced every 2-3 years.

Have you checked for spark when the engine peters out on the water?
Can you duplicate the same problem on the trailer?

I think you are right about diagnostic time. The guage is between a quarter and half while running, sorry, I don't remember the temperature! I did not check for spark when it died, the last time I thought to do it, but had left my spark plug wrench at home and yes I know that was a no no lol!! By the time I got back home, it started up again. I am thinking it may be time to find the thread about changing the impeller..... Doesn't look like fun!!

 

[NikeR6]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

I should also add that I just saw that there isn't a voltage regulator where the manual says there should be one??? I searched hi and low, but did not see any loose or dangling wires that would have gone to one. I talked to someone who said if somebody had changed the alternator to a different kind it wouldn't need the regulator?? Is this correct? Has anyone heard of this before?

 

[RogersJetboat454]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

I should also add that I just saw that there isn't a voltage regulator where the manual says there should be one???

Which manual are you using?
If it's a Clymer, or Seloc they can often lead people on wild goose chases with misinformation (ditch it if that's what you have).
A factory manual is the best.
If I look up a 1984 OMC 2.5, both engine model numbers show the engine as being equipped with a Delco Si series alternator which is internally regulated.

No need for a spark plug wrench either (at least to check spark). When you die out, pull the one of the boots off the plugs, or the coil wire off the distributor, and check for spark with one of these;



It's a spark tester sold at most auto parts stores for under $10, and is FAR more accurate that pulling a plug and looking for spark across the gap.

As far as replacing the impeller, this post has a link to some nice pictures on the subject;
http://forums.iboats.com/mercruiser...tringer-impeller-replacement-pics-378358.html

 

[Howard Sterndrive]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

when it quits, if you try to restart it, will the starter roll it over with good cranking speed?

 

[NikeR6]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

Well thank you, that is good to know! I just got the boat on the weekend and have yet to purchase the factory service manual, but will be!!

Which manual are you using?
If it's a Clymer, or Seloc they can often lead people on wild goose chases with misinformation (ditch it if that's what you have).
A factory manual is the best.
If I look up a 1984 OMC 2.5, both engine model numbers show the engine as being equipped with a Delco Si series alternator which is internally regulated.

No need for a spark plug wrench either (at least to check spark). When you die out, pull the one of the boots off the plugs, or the coil wire off the distributor, and check for spark with one of these;

View attachment 204424

It's a spark tester sold at most auto parts stores for under $10, and is FAR more accurate that pulling a plug and looking for spark across the gap.

As far as replacing the impeller, this post has a link to some nice pictures on the subject;
http://forums.iboats.com/mercruiser...tringer-impeller-replacement-pics-378358.html

 

[NikeR6]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

Yes it does

when it quits, if you try to restart it, will the starter roll it over with good cranking speed?

 

[Howard Sterndrive]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

then the impeller/heat related stuff is not the issue.

Yes it does

 

[NikeR6]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

then the impeller/heat related stuff is not the issue.

Ok, after talking to someone familiar with these, he suggested to replace all spark plug wires and points and condenser, so I will be doing that in the next couple of days.

 

[NikeR6]

Re: 1984 OMC 2.5 sterndrive runs fantastic for 20-25 minutes then dies

Just an update, I changed the spark plug wires and the distributor cap and also a new belt and low and behold It ran great all day! Not exactly sure what part made the difference, but it is good!