85 Johnson 115Hp V4 Tach Question(s)

[ulmatms]

This is actually two questions but I'm not sure if one is related to the other. <br /><br />1. My tach (brand new) will read correct RPMs (most of the time) up until 2000RPMs. Anything after that and it goes to zero. Also it jumps around between 0 and 2000 RPMs sometimes but never above 2000RPMs. I haven't tested the charging voltage (tomorrow) but my bet is the rectifier. Does that seem right?<br /><br />2. This is where I am curious. My hole shot is horrible. 15-20 sec just to plane out, sometimes more, and absolutly never faster then 35MPH but usually around 30 MAX. It seems like I am missing a cylinder (or 2???) but no working tach = not knowing engine RPMs. My second question is this. What can kill a rectifier besides reversing polarity?? Could whatever seems to be robbing my power had killed it? I just don't want to buy a new rectifier and have it be killed again because something else might be wrong. Stator maybe?<br /><br />Anyways, CT were 115, 115 115 110. Any info would be apreciated.<br /><br />Adam

 

[Solittle]

Re: 85 Johnson 115Hp V4 Tach Question(s)

Well lets see - While I think you might let us know what kind of boat this is on (age, length & construction). Next you need to begin to troubleshoot the motor before you start putting on new parts.<br /><br />What do the plugs look like? Do they all look the same? What plugs do you have? Can you get spark to jump a 1/2" gap with a bright blue snap? Start there & post back.<br /><br />Compression is great.<br /><br />You would be well off to get a OMC shop & parts manual for your motor. You will save $ in just getting this motor sorted out with the manuals.

 

[piniongear]

Re: 85 Johnson 115Hp V4 Tach Question(s)

What do you have the setting at on the backside of the tach? #6? If your rectifier is out, the volt meter should be pegging the needle when you are running.

 

[ulmatms]

Re: 85 Johnson 115Hp V4 Tach Question(s)

Sorry, thought I posted that information. It's an 82 performance bass boat. It's around 17'6" long and made of fiberglass.<br /><br />The spark plugs are brand new. I don't remember off hand the model number but they are the champions that are suppose to go with that motor. I will pull them as soon as it stops raining and write back what they look like.<br /><br />I figure the rectifier is the tachs problem (will test when stops raining) because I connected my new tach to a friends boat and it worked fine (6P setting for my motor right?).<br /><br />Also, can't test spark untill stop raining also.<br /><br />I was just wondering if there is something on the motor that can go out and kill the rectifier.<br /><br />Adam

 

[ulmatms]

Re: 85 Johnson 115Hp V4 Tach Question(s)

UPDATE:<br /><br />After conpleating testing here is what i have come up with.<br /><br />1. In using a test I found from Joe. I attached the grey wire going to my tach to the yellow/gray wire comming from the rectifier. Bingo, the tach worked. Bad Rectifier from what I can see.<br /><br />2. Did a test of the charging coil that was in my repair book. I got 110V from one side and 95V from the other side. The book said that i should get 150V or more from both. Is this right? Should I replace the charging coil?<br /><br />3. Spark plugs looked fine.<br /><br />4. didn't have time to test the spark.<br /><br />Any thoughts??<br /><br />Adam

 

[ulmatms]

Re: 85 Johnson 115Hp V4 Tach Question(s)

anybody?