93' Merc 175, tach reads high

[redssv]

93' Bayliner with twin 175's. Port engine runs<br />great and looks fresh. Starboard side has multiple problems. I am weak with 2 strokes, and<br />strong with 4's. So, starting from the top.<br />1. Customer says engines have excessive blue<br />smoke. The oil injection system has been removed,<br />so one gallon of oil is added to every 50 of fuel.<br />2. Customer replaced the spark plugs, with no<br />change.<br /> I asked if he had ever had both engs de-carbed, and he said the last time was four years ago.<br />This customer did not tell me that his tach was<br />1k off, or that his volt meter was stuck at 12V.<br /> Upon first inspection I found the upper voltage<br />regulator yellow wire connections were overheated<br />with 6 volts on a dvom at idle. Im sure the reg. is bad, and I need to test the stator.<br /> How do you properly test this type of system?<br /><br /> As for the tach, I found the #1 coil was inop.<br />I replaced the coil and the tach problem went<br />away for about an hour. The problem came back<br />after I put the upper cover on. So I wiggle tested the power pack wires, and all hell broke<br />loose. I found the outter power pack wires melted together from wire insulation failure.<br />The wires on the inner power pack were shorting<br />(with burn spots)to the upper pack.<br /> I will suggest the customer replace everything<br />because it will improve my chances of a fix.<br /> I learned that my high $$ snap on timing light<br />is worthless on 2 strokes. My fluk 88 will not<br />read ignition dweel. And this is what they call<br />"Flying by the seat of your pants". Please help<br />me get out from under this shade tree.

 

[WillyBWright]

Re: 93' Merc 175, tach reads high

Welcome to iboats and get a manual.<br /><br />You can find them at public libraries. They'll be near the car manuals of yours has them.<br /><br />Your timing light should work fine on any motor that produces spark. If it has a built-in tach, it'll read double of actual. The motor doesn't have points, so you won't be able to get a dwell reading. It also produces a much higher AC-like voltage (around 230) to the coil primaries, not 12vdc. You can use your Fluke with something called a DVA adapter which may be hard to find.<br /><br />The excessive blue smoke probably means sticky or clogged bleed valves. They can be removed with a 5/16 wrench and cleaned with carb cleaner. There also restrictors available that can significantly reduce that smoking a bit, but...<br /><br />It's too bad the oil pumps were removed. Bad Idea! That's probably the main source for the smoking. At idle, the pump mixes the fuel/oil at around 100:1. So by premixing instead, he's stuck with twice the oil and obviously twice the smoke. Sorry, but I have no sympathy for him regarding the smoke. He caused that all by himself. Not much you'll be able to do about that besides cleaning the bleed valves. Don't waste too much time on that.<br /><br />Remove the yellow stator wires from the voltage regulators (I think you'll find two regulators on each motor). There should be continuity between them and no continuity to ground. If you get no continuity between them, there's a broken connection or wire somewhere in the stator. If there is continuity between either and ground, there is a wire shorted to the frame somewhere. In either case, the stator would need replacing.<br /><br />If only one cylinder doesn't have spark and you have a new coil, then I'd expect a bad switchbox. It could be the one that the primary wire is attached to, but it could be the one that you'd think is good. I know that sounds crazy, but it's true.<br /><br />I hope some of this helps. Good luck.