1990 GT175 Ignition Question

[dwco5051]

Time to get back working on last years project. My engine would run well for 10 minutes or so and then would die dead around 1900 RPM. Put a timing light on it with muffs in the driveway, 5 cylinders give a flashing on the timing light about the same. Top starboard lights the timing light like a searchlight. Anyone ever have a similiar problem. ?

 

[emdsapmgr]

Re: 1990 GT175 Ignition Question

Ignition problems tend to show up when weak electrical compoents start to come up to normal operating temps. The timing light test is a good one. I believe you have solid spark only on 1 cylinder-if I read your comments correctly. Clearly an ignition problem. You can do some swapping of coils and see if it makes a difference or not. Coils usually have very low failure rates. Since you only have one power pack on the engine, you don't have the option to swap it like the older models. The pack is a likely culprit, as probably has the highest failure rate on these engines. Since they are in the $300 range, I'd hate to recommend it's replacement when the stator and timer base are the other two major ignition components. If you have a factory service manual, it will prescribe tests for the pack and those other components that will definitively identify the problem part. If you are talented electrically, you can decide to troubleshoot it yourself-or may decide to take it to a reliable shop. A good shop tech can sometimes find things quickly, reducing shop labor so that it can be a least-cost option.

 

[dwco5051]

Re: 1990 GT175 Ignition Question

I may have explained my problem wrong. Five cylinders fire the timing light at a rate to be expected on a engine at idle. The one wire lights up the light at a rate that you can not see a flashing light but at a rate so fast it seems to be just a constant bright light. I haven't been able to find a wiring diagram for this motor yet and the closest mech I know that might have one is over 50 miles away. Since I am just finishing up a new home and getting ready to move time is at a premium right now to take half day and chase him down. As soon as I can I plan to go out to the lake, hook up the light and see if there is a complete ignition failure a high speed. The other thing is when it does act up it will run right up with the fast idle lever in neutral. Maybe something in the lower end if binding. Also I can't find a shift switch on the model thinking it my be defective. Hoping to be able to tie the boat to the pier when it acts up and see if it will wind out in reverse. Risky thing to try on open water with a bass boat.

 

[emdsapmgr]

Re: 1990 GT175 Ignition Question

Thanks for clearing that up. Good fire on 5 of the 6. I'd probably start by trying to eliminate the coil on the bad wire from the problem. Swap it with any of the other 5 good ones. If you want to further troubleshoot this, you will need a factory manual and a peak-reading voltmeter. You need to see 175 volts on a peak reading volt meter out of each plug wire. You can get the manual from Ken Cook co. in Milwaukee. Running up the rpms in neutral does not mean anything. It will do that with 3 cylinders firing. You can put it under load by tying it to the dock and let it idle in forward.

 

[jonesg]

Re: 1990 GT175 Ignition Question

theres peak reading voltmeters on ebay all the time.
you kinda need it to do proper testing.

 

[dwco5051]

Re: 1990 GT175 Ignition Question

I think I may have found my problem. Bought a peak reading voltmeter adapter for my clamp on multimeter which plugs in where my jacks are and for 22 bucks turns a good digital meter I already owned into what I needed. Everything read out OK. Borrowed a good power pack from a friend, tested the boat and after ten minutes the same problem. Tried to see if I could replicate it in reverse tied to the dock and on the water but the prop cavitates too much to load the engine. Finally after trying all other things such as unplugging the main harness, starting it with a jumper switch and shutting off with the choke, grounding the quick start thinking it could be cutting in on the water, etc., took it home and spent hours checking everything electrical on this motor. Eventually found one of the wires coming out of the regulator/rectifier almost touched a clamp and had the insulation worn off and corrosion on the exposed wire but wasn?t touching while cold. Cut a piece from a plastic soda bottle for a insulator, took the boat back out on the water and the problem went away. It still has some roughness now and then but since this boat sat for almost three years with gas in it and no stabilizer I knew I was eventually going to have to rebuild carbs.

New question. Are these plug wires shielded cable? My clamp on inductive timing light doesn?t seem like it works as it should when checking spark but I can back my spark tester out to about 5/8-3/4? and still show a strong spark jumping across it.

Thanks for all the help given on this board so far.