3.3 VMax RPM drop

[mulligan]

So I stumped the Yamaha pros with a little problem with my VZ250 and was wondering if anyone ran into this problem.

A little back history.  About a month ago the motor was dogging and sputtering some.  I took it in and they found that the TPS was working intermittently.  They replaced the TPS and all was good...so I thought.  The motor now purrs like a kitten at low speeds and runs like a scolded dog on top.  The issue is that if I cruise around 3800rpm it will every once in a while drop down a 100rpm or so for a split second then pick right back up.  I took it back in thinking it might be the new TPS but that all checks out.  Curtis and the guys at Family Boating have it now but are having a hard time pointing out the problem.

Curtis and they guys are the best around so I know they will figure it out but was wondering if anyone has ran into this issue before?  Thanks  

[linesider 159]

I know mine did it.  Several guys on bass boat central talked about it happening. It just seemed to hate that rpm range. 

[smilemaker]

I will have a better reply in 3 days but for a long time I have been having problems with my 04 200 hpdi dropping several hundred rpm and running sluggish at higher end.

Over last 2 years it has had all new fuel hoses numerous filter changes and the injectors serviced with mystery filter changed. Each time things improve but not completely.

All checks out ok on the yds laptop. Well I now believe that the problem is with the old coils cutting in and out due to age and poor grounding to the block at the mounting location. Ordered new coils and will find out fri if they make a difference and let everyone know.

[lurem]

I it almost sounds like a ecm/power pack cutting out. Gonna be really hard to pinpoint if it is unless you have a friend with the same motor and you borrow it for a few days.

[mulligan]

Thanks guys.  I was thinking coil as well but would have thought the guys would pick that up.  I did get a call and they ran it on the lake with 2 people, one driving and one on the laptop.   They gathered all the info and sent it direct to Yamaha for them to look at.  Fingers crossed.

[smilemaker]

Here is where  the diagnostic problem  comes with the yds program. It tells you the ecm sent a signal to the coil to fire but that does not mean that it fired. If the coil is bad or sparkplug is bad the ecm does not know that. The best way to tell is with a timing light between the coil and spark plug. This will tell you that the signal got past the coil but not necessarily how strong.

[smilemaker]

Mulligan. Today I put on 6 new ignition coils on my 04 200 hpdi. Went out and ran it hard for 2 1/2 hrs from idle to full throttle 5300 rpm max 50 mph. No cutting out and the response was like it was new. I know many say a coil is either good or bad but after replacing all 6 it was a totally different engine.

[Capt. Troy]

On 7/26/2017 at 5:14 PM, smilemaker said:

Here is where  the diagnostic problem  comes with the yds program. It tells you the ecm sent a signal to the coil to fire but that does not mean that it fired. If the coil is bad or sparkplug is bad the ecm does not know that. The best way to tell is with a timing light between the coil and spark plug. This will tell you that the signal got past the coil but not necessarily how strong.

This^^^

 

I had the Yamaha factory guy riding in the boat with me to find a miss at high RPM. Spent hours with the lap top hooked up. After throwing  some parts at the thing they put in new spark plugs. Problem solved. Something to do with the plug resistor. It was such a quick miss the computer could not pick it up in the scan. This was a 2010 VZ 250

[mulligan]

Thanks guys.  After 3 weeks, 7 total this summer they still have no answer for me.  I know they put more new plugs in, "old" ones had maybe 5 hours on them, other than that I'm not sure what they have done.

[smilemaker]

After numerous hrs reading and talking there are some things I came to understand. One of the big things with a yamaha is that it is backwards of a car when it comes to electronics. On the outboard the positive is always on and the ground is cut on or off to complete the circuit. On your radio and depth finders it is the positive that we cut on to complete the circuit. It is important to know this when troubleshooting.

With this understood you realize that the Ecm works by grounding to send the signal for a function to work. The other thing is that the yds program only tells you part of the story. As far as coils and ignition are concerned it only tells you that it sent a signal to the coil it does not tell you that the coil passed the information to the spark plug. If you hook a timing light to the plug wire on each signal it will let you know if the coil sent the signal to the plug but the Ecm does not know this. The coil has a specification for resistance that you can check statically but when it gets hot you don't know if the coil is breaking down while running unless you have a timing light on it.

The other factor is that the spark plug cap is a removable piece with its own resistance. With all of the confusing info and sporadic nature of my problem is when I decided to replace all the coils. At worst I figured that after 13 years a stronger signal from the coil could not hurt.

If the motor continues to run I would say the lesson learned is that if you are dropping a cylinder or dropping rpm while under way then get a timing light and check the integrity of the coils under a load and don't rely just on the programs. 

[ififish]

X2 on new plugs and check to see if the ceramic is cracked.  Mechanics cracked 4 of 6 previously. Mine had plugs with less then 10hrs and were fouled. Cleaned with carb cleaner then changed to new. Keep old as backup. Cost me half of my vacation fishing. Napa and Autozone sell the plugs for $4.95.

03 vz250

[smilemaker]

When getting plugs from auto parts store be sure to get the exact same plugs with the dual  tips. Auto stores are notorious for giving a substitute from a cross reference but you need to be picky with the Yamaha compared to the Kia 

[mulligan]

Well after the boat being at both FBC locations and having techs at both shops banging their heads over it they finally found the cause, I hope.  They found that when running the motor between 3400-3600rpm there was a very slight dip in fuel pressure which made them think it was the injectors or fuel pump.  I just had the injector flow tested and cleaned not long ago so that left the pump which honestly made no sense to me thinking if it was the pump it would not run well at high rpm.  They called Flagship, pump rebuild shop, where they said to check something out before sending the pump in for a rebuild.  Flagship nailed it, a few small holes at the very top of the exhaust tuner.  From my understanding the motor needs a certain amount of back pressure and at the 3400-3600rpm it was losing just enough pressure where the computer was retuning the motor.  We shall see.

[lurem]

WOW! I am glad they found it! I think that is the same problem that Joe (Dabear) had with his 150. The exhaust tuner had a leak and it was messing with the signal on the O2 sensor causing it to run erratically. Curtis diagnosed that on Joe's a few months ago after an extended visit to the shop. Sounds like it may be a common theme on the Yamaha's.

I have a couple exhaust tuners at the house from failed experiments if you need on from a 115 HP and you can make it work! haha

[dabear]

  Dale/ Lurem Family Boating Center did a outstanding job with my motor diag .  FBC diag the old motor ,took it in trade and did a Repower for me. After the diag we talked about a trade in and Repower. As soon as I made up my mind which way I wanted to go , they ordered and installed the new motor. This wasn't the same problem my old motor had . It wouldn't idle with the cowl on in the water. The map sensor was picking up rich exhaust fumes and sending false signals. The plate that the block bolts to had corrosion and leaked between the power head and exhaust plate not the tuner . I wish mine was just a exhaust tuner replacement and not the block and exhaust plate surfaces corroded . Yamaha has a kit to correct this fault on several models the part number is MAR-EXHKT-04-00  $707.15 for parts. 

Mulligan I do hope that that thing is up and running 100% again soon . 

[lurem]

Dabear, It wasn't meant as a dig on FBC. I was saying that Yamaha seems to have a problem with its treatment process of its metals. Mulligan's motor was older but your was fairly new and both had corrosion eating away and causing problems.

[dabear]

No problem Dale , I just wanted to make it very clear that I was and always have been treated more than fair at Family Boating Center. After Paul and Curtis calling Yamaha about my old motor Yamaha did help some to make the total package of my repower a fair deal .   Joe R

[mulligan]

Well I finally have the boat back and working the way it should.  They thought it was the tuner and it may have been part of the issue, there was a small hole on the inside and one of the gaskets did have a leak.  I had them replace the tuner.  After the tuner was replaced I went on a wet test with the service manager.  The motor ran like crap.  Rough Idle, no hole shot, and would only turn 4800 RPM.  Back to the drawing board.  It when on the computer and the YDS had a low voltage alarm that was kicking into safe mode and the cable going from the battery switch to the motor did not look to healthy.  So I picked the boat up ran all new cables from the battery to a new switch and then to the motor.  Took the boat out yesterday and she ran like it should all the way to 6k RPM.  I did not play with it too much with the rain coming in and the chop but all seemed good.