Yamaha 2002 150 HPDI Twins losing RPM's

[IGWT]

Hello, this is my first post on a forum like this (repair). Well this is what I am having problems with, I have twin 2002 Yamaha 150 HPDI's and one of them (starboard) started losing RPM's at over 1700-2000 rpm's. It would lose about 500 rpm's and come back RPM's up and down until I pulled back on the throttle. It seemed to work ok at under 1700 rpm's, but maybe I just did not notice. Now for some history on the boat, I have had it out of the water since last October to remove the bottom paint, fixed some fiberglass, and gelcoat the bottom. When I took it out after this period from October to the end of June the first run, the motors were fine. After a minute or so the starboard side motor started to lose the RPM's and surge back only a few times, then I idled for a while through the Idle zone in the inlet. After the idle zone kicked the speed up and the motors have run great since (about 10-20 hours) that vacation week. I took the boat out yesterday and boat ran fine getting out and running all day (mainly drifting so probably only 1 hour running), on the last drift we decided to run south and set up when I started to feel the power loss and surging. The motors had a full service about 70 hours ago, changed the VST filters about 50 hours ago. Not sure where to start here, any help would be great. Thanks

 

[cousinabe]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

was the medium pressure filter changed?
#20
http://www.boats.net/parts/search/Yamaha/Outboard/2002/Z150TXRA/VAPOR SEPARATOR 1/parts.html

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

I had the motors serviced in May of 2009, the Port side motor has a date on the filter of 5/09, but the starboard side motor (that has the problem) does not have a date on the filter. I would guess that it was also changed as I paid for the service of having it changed.

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

One other thing, I just looked over the motor and it seems like the port motor has Filter assembly full of fuel where the starboard side has the fuel level about 1.5" lower than the cap (around the bottom of the filter element).

 

[cousinabe]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

just to be clear, that motor has three filters; a VST and a medium pressure and the filter element where you stated is low on fuel. That is ok to have a low level there.
also, has low pressure fuel pumps that should be changed every few seasons.

outside of your motor, you will also have fuel water separators that could be clogged too.
look what you paid for in parts and report back.

If you have a laptop and diag software, you could monitor the fuel pressure.

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

Thanks for the help cousinabe, really do appreciate it. I do have a laptop but do not have the diagnostic software to monitor the motors. Where can you get the software? I went ahead and purchased the parts you mentioned and should be able to install them fairly easily with the exception of the HP filter. Remember there was a trick to this one?

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

Well I replaced the water Separator, HP filter (strainer), fuel filter in clear canister, and I went out to test, at the beginning it seamed to be working as the motor did not hesitate, but I did not go over 2600 rpms as the seas were bad here out of PBI. But again on the return trip the same loss of RPM's on anything greater than 2500 RPMs it would go down to about 1100 and back up. It did seem to stay at the lower RPMs a little longer than I noticed before.

 

[rodbolt]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

you MUST monitor HP rail pressure AND medium pressure at the SAME time AT the PROBLEM RPM AND LOAD.
failure will result in posting about blown pistons.
the HP rail can be monitored with a DVM, some jumper leads and some paper clips.
but it MUST be done together.

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

Well took the boat out and put the computer on it today, while I was waiting for the failure to occur the port side motor picked up the same symptoms. Well the results from the test was both motors pressure dropped from approximately 680 lb to 150 lbs at failure.

 

[rodbolt]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

all well and good, however you only did a half arsed job and all we can tell you is you lost high pressure on the rail. however had you ALSO moniyored medium pressure we could have told you which one of the 3 fuel subsystems is failing.
yu have 3,repeat THREE, fuel systems on that motor,low pressue. this includes everything from the liquid level in the tank to the VST inlet, medium pressure. 50 PSI anytime it is running.
this includes everything from the VST inlet to the High pressure pump inlet.
then you have the HP side that includes the belt,HP pump, rail and 6 injectors.
thats why its IMPERATIVE to test BOTH medium AND high pressure at the SAME time at the RPM AND LOAD it fails.
if both drop look at the VST internal filter and the low pressure side,if medium remains at 50 and HP fails look at the inline filter between the VST and HP pump or the HP pump internal filters,not field servicable.
keep running it lean and you WILL post about detonated pistons. take it to da bank.
yearly maint includes the VST filter and the medium pressure inline filter, engine filter cup and hull fuel water seperator is every 6 months OR 50 hours whichever occur FIRST.

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

Rodbolt, understood I was not sure exactly how to check the medium pressure. I did change out the VST filter on one of the motors and attached a picture of how it looked. Is this enough to cause the loss of RPM's

 

[rodbolt]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

more than enough.
you also need to change the medium pressure inline filter as well.
you MUST use the correct oeticker type clamp when doing it,
DO NOT use standard hose clamps.

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

I changed the metal filter two weeks ago, but did not change the VST filters as the one in the picture was replaced April 2009. and only had approximately 50 hours on it. I will be taking it out for a reun Wednesday...

 

[rodbolt]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

if you put a clean filter in at breakfast and inroduce trash in it at lunch,guess whats for dinner?
thats why you do them all at the same time.

 

[IGWT]

Re: Yamaha 2002 150 HPDI Twins losing RPM's

Took the boat out after changing now all the filters. Boat ran great, back up to 5100 RPM WOT without hezitation. Was out all day today running at different speeds...

Thanks to all who helped solve the issues I had...