Tach problem

I have a 19 ft. 2003 Key West Center Console Sportman fishing boat. I installed my old 1985 Evinrude XP 150, which has been sitting idle on my old runabout for the past twelve years without use since 1988. To convert to the 2003 instrumentation I used OMC’s conversion kit to adapt my 1985 engine’s electrical to the 2003 Key West.<br />I also converted my engine from the no wire VRO to the new four wire VRO, using the recommended conversion wiring harness.<br />Everything, warning horns, lights all seems to work ok until a few days ago, the tach went haywire. It will zero out when the key is turned on and when the engine starts, it will go up to 800 Rpm’s or so and fall back to zero.<br />The Voltmeter registers 12 volts with the key switch on, and 12 to 13.5 with the engine running at idle speeds.<br />I disconnected the Tach terminal and reconnected it without success. The tach is sill lame. Any ideas or suggestions will be greatly appreciated.<br /><br />Thanks,<br /><br />DoferGofer.

Re: Tach problem

Might be the rectifier. You can look in your manual for the procedure to test the rectifier or ,if it's a Teleflex tach, you can use your volt meter to check it. Connect the meter between "Gr." and "Send" on the back of the tach. It should read 3.5VAC at idle and 5-7VAC at approx. 2000rpm.<br /><br />c/6<br />Hooty

Re: Tach problem

Thanks Hooty,<br /><br />I will check the rectifier. All of the wires are tight and there is not any corrosion at any of the connections.<br />The tach is a 2003 OMC with system check. The voltmeter does not show over 13.5 volts at idle.<br /><br />DoferGofer

Re: Tach problem

Hooty,<br /><br />After reading my manual on testing the rectifier. I don't have the equipment to test the 35 amp. charging system. I will use it like this for a while and then try a new tach.

Re: Tach problem

Does your manual show how to check the rectifier diodes?<br /><br />c/6<br />Hooty

Re: Tach problem

Hello Hooty,<br /><br />My manual shows a Rectifier Ohmmeter test for the 60, 75, 90 ML and 100WML but, not for the V4, V6 TL and TXL Models. For the V4, V6 TL and TXL Models my manual shows a different test, using a variable load tester, which I don’t have, or access to.<br /><br />At any rate, I took her out crabbing yesterday for about five hours of constant running. At the beginning of the trip the motor started up and ran fine out of the mariner. Once I started to accelerate it stumble and sputtered I pulled back and then it cleared up and ran with a few misses for about couple of minutes. Then ran just fine out to my crabbing spot, about five mile trip. The volt meter show about 13.5 volts at idle and when moving along at about 30 miles an hour the volt meter show about 14 volts and my hummingbird 400 TX show a volt reading of 14.5 to 14.9 volts. <br />While crabbing at speeds of 2, to 2.5 mph (GPS) the voltmeter and hummingbird 400 TX, show 13.5 volts. Therefore, I am going to assume that the charging system is ok and that the tach is just bad and I need to replace it with a new one. <br /><br />Back to the sputtering and missing, I am going to pull the plugs, which have about twenty-five hours. Also, I am going to ohms test the coils and rebuild the carburetors, since they have never been cleaned since I bought the engine new in 1985. I suppose they are due since the engine sit unused for 12 years. <br />One other thing I didn’t mention, I ran a compression test after the first outing, and the results were all six cyclinder were at 60 lbs. After decarbing, and about twenty hrs of use. the compression now is Port side 115, 112, 112, Starboard 115, 114, 116.<br /><br />Finaly, I notice a lot of black ooze running down the outside the exhaust housing, this was very bad when I first start using the engine but, has slowed very much after twenty-five hours of use. But, never when it was new.

Re: Tach problem

Opps Hooty,<br /><br />I forgot to metion that the tach worked at crabbing speeds of 2 to 2.5 mph (idle speed pulling traps or running trotline) until I increased rpms and poof, the tach was back to zero.

Re: Tach problem

Well, it zounds like the rectifier is ok. You can still test if the tach is ok or not by using your volt meter instead of the tach like I described above. That's a check for a Teleflex tach but I'd bet it would work on your's.<br /><br />c/6<br />Hooty

Re: Tach problem