UGH... can anyone help that knows 485 Mercs

DouglasMB

DouglasMB

New Member
Apr 22, 2012
131
Eastern NC
Boat Info
1981 sea ray 255 amberjack
Engines
2 185 mercruiser
I have been out of the country and now I am am home trying to get ready for the 4th. My engine will not start :( My brother and I ran the boat over to get gass yesterday to beat the crowd and after I shut if off it would not come back on.

It's the lead engine (with power steering and alt) It's dragging like it can barely turn over... then when it does it cut right back off... the engine turns over freely by hand... and when you take out plugs it turns over with no issues. But with only 2 plugs in it drags and wont turn over. We are going to try to swap starters and see if that is it, but we have never had any trouble and it is relativly new (the starter) it is an marine starter and just bought last season. I really am not a mechanic, my brother is doing most of the work. I am far from dumb though and I learn very fast, this is just not something i have ever needed to do. Has anyone had this sort of problem and might know what direction to point us in. We are going to work on it tonight and tomorrow to try to get it up and going for the fourth to take the kids to see fire works.

thanks

1981 25.5 AJ with 2 IO 485 Mercs
 
I would like to add... my brother said that it could have jumped time but not likely... he is a car mechanic not really a boat guy... but he said if it burns gas and creates power and I can get a book on it then he can fix it lol I just thought I would see if anyone who has gone through this might already be able to tell me to save me some time
 
Battery is only about 2 months old and has only been used 3 times... we did notice all the posts we a bit loose so they are not getting a good connection. Maybe just throw a battry charger on it and cross my fingers?
 
Hello
Is there any chance of water ingestion if you have water in the cylinders it will not compress and chug to turn over you could try another battery but if you have any water you don't want to keep trying to turn over check your Barttery first then starter . Did it start fine when going over to gas dock did you come of of plane to quick
 
I think it did start a little sluggish... I was thinking too that we have gotten a sick amount of rain here lately... I have had to use my bildge a lot. So I may have weakend the battery quite a bit too.
 
Hello Douglas
Then I would fully charge battery and try again before you start tearing things apart keep it simple before you start questioning everything believe me ive been there thinking of everything that could happen when the majority of the time its the obvious simple thing good luck and happy fourth
 
Like my father used to tell me all the time... "keep it simple stupid" lol
 
I am back in town now... and to update we took the boat out for the fourth to enjoy the fireworks... both motors started up just fine and were running great... only when they were warm did the other motor again not start and act like it was "dragging" like it had a low battery or a bad starter. I came back out the next morning once it cooled off and again both started perfectly... so it only has this issue when it is hot. (not overheater just general use)

My brother said it could be many things... coil, starter... on and on... Maybe you guys have had the same issues?
 
I have never experienced it on the boat, but cars will have issues when the starter is located closely to the exhaust. It will absorb the heat and following a heat soak the resistances will make it drag. I would not discredit the cables as well, as they can have the same problems.
I would do a voltage drop on the starter cables (pos and neg). If you have less then .5V on pos and .2V on neg check the battery to be sure it is good. If all that looks good you may have a starter issue.
I will say that I had a previous boat that the manifolds were leaking slightly and after running and then sitting for a while (the longer I sat the worse it was) it would crank slow. There was enough water in the cylinder to make it crank slow, but not enough to make it hydrolock.
Is it hard to start cold after water could leak in this may be a possibility, but you said they start fine cold.

A hot coil may make a hard start condition, but not a slow crank.

You may also want to check the timing when it is running to be sure it isnt advanced too much. Not sure how much "drag" you are experiencing, but some will advance the timing too far and it makes it harder to start.
 
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Could be timing too. http://www.*******.com/merc/Bullet/87/87_17.pdf I can't get the link to come up correctly? But Mercruiser has changed the base timing from 8btdc to 4btdc on your engine,because of the chitty gas we get these days.This too will cause an engine to crank slowly when hot.Hope this helps.
 
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