1985 Merc 150 ...Bad Trigger?

[dakk1]

1985 Merc 150 Black Max on a 17' Stratos Fish/Ski<br />This is an ongoing multi-year boat project.(LOL).<br />Original problem was the much bally-hooed engine bogging from take off. I assumed that it was fuel related and have done everything I could think of and was advised to do by the good folks here at I boats. I have, in no particular order:<br /><br />Rebuilt the carbs from kits.<br />Rebuilt the fuel pump.<br />Installed new fuel hoses.<br />Checked compression. (All OK and within 5%).<br />New plugs and wires.<br />Decarbed.<br />Run motor from a Remote tank with clean gas & oil<br />Checked vents.<br />Checked for water in LU and Replaced old Lube(OK)<br />Installed new water pump.<br />New thermostats.<br /><br />Today I turned my attention to the ignition system and per the Merc manual did the Stator Test (OK) and the Trigger Test. The Second set of leads I tested from the trigger to the switch boxes read 8000 ohms! Manual specifies 1100-1400.<br />Why the HIGH reading? (For educational purposes)<br />This is between White Trigger Lead(without yellow sleeve) and Violet Trigger Lead (with yellow sleeve).<br />HAVE I FOUND MY PROBLEM?<br />Would this lead to the symptom of bogging at take off? Or is this a symptom of some other problem?<br />Sorry for the long post. Any and all help appreciated. Dave.

 

[DHPMARINE]

Re: 1985 Merc 150 ...Bad Trigger?

Dave,you may be on the right track.Are you using the DVA tests before the ohm tests?I think the manual does the DVA first,and sends you to ohms second,only if the DVA is off.Ohm readings vary,with temp as well as what setting you use (x1,x10,x100,etc.).<br /><br />Also yellow banded stator wires and yellow banded trigger wires have to go to the same switch box.Found this once,but it had me going in circles.<br /><br />DHP

 

[Barnacle_Bill]

Re: 1985 Merc 150 ...Bad Trigger?

I happen to have one of those triggers and checked it. I got a little over 1200 ohms reading the same wires. So 8000 ohms is way out of tolerance. DHP is correct about the reading varing with temperature but I don't think it would be that much. IMOHO

 

[dakk1]

Re: 1985 Merc 150 ...Bad Trigger?

Update on 1985 Merc 150 XR2.<br /><br />Tested for spark today and # 4 has NO spark. Others seem OK. At least they have spark across 3/8 inch.<br /><br />Tested the compression again since I was there so to speak. 109 lowest to 114 highest.(Cold).<br /><br />For now I'm assuming it's the Trigger Assembly from the previous OHMS readings and will replace.<br /><br />Thanks to DHPMARINE and IBNFSHN for the replies.<br /><br />Anyone else been there done that I would like to hear from you. Dave.

 

[CU2NITE]

Re: 1985 Merc 150 ...Bad Trigger?

I have been there before(same symptoms), my problem ended up being the switchbox. If you change your switchboxes around and you loose spark to a different cylinder you have a switchbox problem. This is a very common problem with this motor. Good luck and let us know.<br />CU<br /><br />-------------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[CU2NITE]

Re: 1985 Merc 150 ...Bad Trigger?

Have you figured out your problem?

 

[dakk1]

Re: 1985 Merc 150 ...Bad Trigger?

Update on 1985 Merc 150 XR2.<br /><br />Thanks CU2NITE for the reply.<br /><br />Since last post I have cleaned all the ground wires from the coils and the leads from the switch box to the coils and I now have spark on all 6 cylinders.<br />Honestly, I'm surprised since I had cleaned them<br />a couple of summers ago and they didn't look that bad. Only slight oxidation around connections and actual contact surfaces looked pretty good. Could be one of those intermittent failures I guess (Oh,joy).<br />I think I will unwrap and inspect/test all these wires from coils to switch box. One could be grounding out somewhere I guess.<br />I Re-tested (OHMS test) the stator and trigger leads, just to double check, and that one set of leads from the trigger still reading 7600+ Ohms.(Should be 1100-1400).<br />I agree, one or both of the switch boxes are more than likely part of the problem, at least. I'm wondering though, if a bad trigger could cause the switch box(es) to fail. Anyone know?<br />Having to do this a couple of hundred bucks at a time if you know what I mean.(LOL).<br />Any and all suggestions welcome.... Dave.

 

[Mike Caspari]

Re: 1985 Merc 150 ...Bad Trigger?

Higher ohms means more of an open and maybe off timing on the affected cylinders. If you have problems I'd change the trigger as per service manual instructions and eliminate that possibility and maybe save a switchbox down the road. I'm not one for using the process of elimination but the volt/ohmmeter reading has to be givin some consideration. Good luck.