Need help with Merc V150

[LaGaviota]

I have written in before. This is a 1984 V6 150hp merc outboard. She boggs down at WOT. I have a new gas tank, new lines, fuel pump rebuilt, clean carbs and jets. A mechanic did a diagnostic on Friday on the electrical for me and told me that the compression is 125 on 5 of 6 cylinders and 100 on the lower port cylinder. He said that I have good spark on all cylinders. Some times it will run at 4000 rpm and then drop down to lower rpm. For about 10 minutes, it ran at over 5000 rpm and then dropped back down to 4000rpm. I pulled the fuel pump apart and re-inspected and sprayed carb cleaner into check valves. Afterward it ran at 5000rpm and then dropped back down to about 3000rpm. It is staying at about 3000rpm right now. It sounds like it is running rich. What could this be? Is there any reason to change the fuel pump housing or are the valves and diaphram and gaskets the only important part? HELP

 

[CharlieB]

Re: Need help with Merc V150

I suspect that it runs about the same length of time from stone cold before it exhibits problems right?

Longer if you keep the RPM down, less time I you're pushing it harder, higher RPM.

An electrical component is heating up and breaking down, less RPM is less load and less heating.

Unfortunately these are the harder problems to solve, it MUST BE TESTED WHEN IT IS FAILING.

Invest in a DVA meter, the cost is cheap compared to the electrical parts that you could be purchasing in error, so you want to be double sure that you are buying the right part the first time.

Test the stator and trigerat idle on the hose at home, then figure out how you can run wires such that you can test on the water. Re-test the stator and triggers on the water both before and during the problem. Write dow your readings, The faulty component should be appearant by the lower reading when heated.

Be careful, good alligator clips and LONG leads, and plenty of caution.

 

[Laddies]

Re: Need help with Merc V150

It may be a electical problem as meantioned above, but I still wonderabout fuel are all fuel lines free of kinks, when the carbs were cleaned did anyone see if the trash screens were gone(as recommended by merc) are the high speed jet in the proper carb. if this stull was done then must go to the ign and start with a induction tach on the plug wire oner at a time to see if you can find one or more cyls missing it is important to ck them all as it will give clues to what has failed

 

[LaGaviota]

Re: Need help with Merc V150

Thanks Charlie B and Laddies. The fuel lines are clear. No screens in the carbs. I have no idea if the jet sizes are right, but it has run for about 15 minutes at over 5000rpm and why would jets fail some of the time? * I paid a master merc mechanic to check the electrical components and he said that I was getting good spark to all cylinders even when it was bogging down to 3000rpm. Can I be getting good spark to all cylinders and still possibly have a high speed winding failure in the stator? I guess I will have to get a DVA and try to figure out the electrical issue myself, but that is exactly why I paid a master mechanic.

 

[LaGaviota]

Re: Need help with Merc V150

Gentlemen, I think that my problem is fuel related and not electrical. I say this because I am getting some different rpms at WOT. Today it ran at 4600rpm and then bogged right down. I noticed that gas was spilling out of the lower port carb and there seems to also be some gas fluttering in a couple of other carbs. I pulled the carbs and cleaned the needles and seats with carb cleaner and they looked pretty good to me. Not exactly sure about my float levels...I just left them where they were. Because of the gas flowing out of the carbs, could this be my reeds? I'm wondering if I should engage in a complete carb rebuild or should I go straight to the reed block?

 

[LaGaviota]

Re: Need help with Merc V150

I have the engine running at 4,600rpm for about 5-10 minutes before it drops quickly to about 3,800 rpm. I am becoming convinced that it is electrical. My master merc mechanic appears to be less than a master. I paid him to test the electrical components and he basically charged me $200 and said that it is getting good spark. So, I have to figure this out on my own. I have an analog ohms meter. Can someone help me test the stator/switchbox/coils, and if pertinent then the rectifier and trigger too? I do not have a DVA and would like to work on this with my current meter if possible. Thanks.

 

[Laddies]

Re: Need help with Merc V150

A OHM meter will fid some problems but has know way the ck for low voltage a OHM meter will find a open winding easily but that is not the prolem you have anyway here are the specs.form CDI