2004 yamaha v150tlrc issue

[timothycan]

2004 Yamaha VMAX V150TLRC issue







Need assistance. 2004 Yamaha VMAX model V150TLRC. Apologize upfront for the long post.

First and foremost before all the she issues boat would run 5500 Rpms and hit 60 mph. Now boat will not go over 5000rpms and only about 46-48 mph. No changes other than what's listed below have been made.

was on the lake and at high RPMs, over 5000 motor was acting like there was water in the fuel or was about to run out of gas. Changed the water / fuel separator. No change after going back out.

then changed spark plugs-same issue. Next time out boat was acting the same at high Rpms. Then fell flat on her face. Started back up fine. Then, under load would not go over about 2500 Rpms and shook bad, only under load. In neutral motor rev'd up fine. Then about half mile from ramp she came alive and seemed to run fine.

took to boat shop and they did the following: removed and cleaned carbs, replaced fuel pumps, checked fuel for water-NONE. Checked fuel line and filters-good. Took her out to the lake, will start and run fine but when she gets to 5000 Rpms starts to "miss" and feels like water in the fuel or like it's going to run out of gas. Drop it down to about 4200-4500 Rpms, boat runs fine.

Took it to another boat shop explained to them what has already bee done and they believed it was an electric issue. Swapped out the CDI, regulator/rectifier, ignition coils and pulser coil. Went to the lake same issue.

So, now boat is back at the original shop, who is a Yamaha certified location.

has anyone ever experienced this or have any idea? Thanks

[rodbolt17]

well you know what it aint.

anyone ever try some old fashioned trouble shooting???
it actually works.
two ways, one is with the hood off and a trusted helmsman that is not on your life insurance or test wheel YB1626.
all testing will most likly be at the speed and load.
your either losing spark, can be tested with a DVA and a DVM.
or your losing fuel, can be tested by squirting premix down each carb and observing.
for testing CDI out I made up a 6 wire octopus so I can leave the hood on and test from the hull while seated.
has anyone cleaned the CPS?
that engine sparks four off 2 pulser coils and the other two are made in the CDI based on the CPS.

[rodbolt17]

those carbs are simple and robust.
I rarely kit them just change the float chamber gasket.
unless it sank I wont remove the large brass screws that cover some machining holes.

there are two pilot air jets that again unless it sunk I wont remove them.
two pilot fuel jets that I do remove and two main jets and it depends on what I find as to removal.
now there are also two back draft jets under a steel plate, leave them alone as well.

I can typically strip clean and reassemble a set on a V6 in 1.5-2 hours.
could be I have done more than one.

[timothycan]

Thanks for the replies so far. It is back at the original shop as well. They did pull, disassemble, clean and reassemble the carbs.

I will contact them and ask if they remember taking them all the way apart including the jets. I do believe that is what they did.

Thanks for all the advise.

[Psalm 99]

Your problem has some elements of a similar problem I had last year. My engine is a 2004 carbed Yamaha 150. On a day out engine ran well for a couple of hours. Then rpm dropped suddenly to around 1600 and didn't respond to throttle. Left throttle at what should have been 3200 rpm and headed for dock. Periodically engine would quickly rev back to throttle setting, sometimes for a few minutes, often just for a few seconds. After going through much of what you've done, the problem turned out to simply be a bad ground wire (there's quite a few). Took each connection off, buffed each, sprayed with CRC electronic cleaner and reassembled. Totally took care of problem. Got the idea on this Forum.

[boscoe99]

Damn good response.

For almost any intermittent problem first check the grounds, check the grounds, check the grounds. A bad ground will cause some mysterious voodoo doo doo.

Unbolt each ground connection and clean it with something like green scotchbrite. Both block side and the terminal side. At that time it costs almost nothing to disconnect and reconnect connectors several times. There might be a milliohm of resistance built within the connector that can cause some weird stuff to be happening or not happening.

The motor is running on but 12 volts. It does not take much resistance in the form of a defective connection to result in a voltage drop. The motor vibrating can cause the connection to be OK for a while, not OK for a while, then maybe OK for a while again. Bad intermittent connections can cause tee totalers to become heavy drinkers.

[99yam40]

I would add to put something on the connections after cleaning to keep the corrosion and oxidation from causing problems again soon