94 SS2 150 tack down issues and a pinging noise

[23regulator1994]

new member here, thanks in advance for any advise that you can offer. I recently purchased a 23 regulator with a twin 150 yamaha setup. the motors are 94 SS2s with about 1200hrs on them compression was perfect at time of purchase in april 2014. we got to take the boat out two times now and have a couple of things going on with the motors.
1) we have had issues with both motors tacking down while under way. both times it was at the end of a long run on a returning trip. Port side first next trip it was the opposite motor acting up. We pulled the sending unit and sucked the tank dry and replaced the filters after the first bout but the opposing motor did the same on the next trip out. All of this with fresh marine grade fuel and fresh filters. I have no idea when the fuel pumps were replaced last so wondering if that would be a good place to start?

2.second problem is we noticed a pinging noise when running at cruise speed. I cant identify which motor it is or at what level in the motor it is coming from. The noise sounds like a metel part making a random ping like its bouncing off of something. I haven't had a chance to mess with the motors to try and identify the source but was hoping someone might be able to offer some trouble shooting advice for either issue.
Thanks again and please do let me know if more info on the problem or motor ID info is needed to properly address the problem. Thnask again!

[rodbolt17]

never heard of ss2s.
aint gota clue what tacking down means.

post a model number and what its doing.

[23regulator1994]

sorry about that I was looking for the books. one is a 150 txrs other is L150txrs. just a saltwater series.
what i meant was we were loosing rpms after runing at cruising speed on an 1hour plus run. the first time we let the motor rest for a second and got it to fire back up and it ran great all the way back in. On the oppisite motor during the next trip the same thing happened but the motor never would get back up to 4k but would run with occasional backing down of RPMs.
1) changing the fileters there was bad fuel in the bottom of the filter so we ditched the old filters and drained the tank. Filled her back up with fresh fuel and had the same issue with other motor on the next trip.

[rodbolt17]

150TXRS
should be the standard 150 carbed 25" motors.
first test the alarm.
this model actually should self test at key on.
to test simply pull the stop lanyard and crank the engine briefly.
alarm should sound.

your describing a loss of fuel in the intake.
most likely carbs/lift pump.
if you do a pump do the carbs.
if you do the carbs do the pumps.

always start with a spark and compression test.

[23regulator1994]

the alarms all work when tested from the key. the compression was 110 +/- half pound accross all cylinders checked right before the first trip out when the issue first presented itself.
I just want to make sure that I understand you correctly when you say "most likely carbs/lift pump.
if you do a pump do the carbs.
if you do the carbs do the pumps."

shold carbs be rebuilt if pumps are replaced? should the new pumps have an adverse affect on old carbs or is this the natural progression of the trouble shooting that we are going to need to go through?

[99yam40]

I believe he does both each time to keep the motor from coming back due to problems still.

[TownsendsFJR1300]

Not sure if you replaced the ENGINE FILTERS or transom (Racor style filters).

With the known crap in the fuel, I would check the under cowl fuel filter (part #5) should any crap have gotten past the Racors (if you haven't already) and potentially clogged up the engine fuel filter:

1994 150TXRS Yamaha Outboard FUEL Diagram and Parts

There should also be a drain screw at the bottom of each carb float bowl. I would use a small container, drain the bowls into the can and check for water/crap. Pump the primer if necessary to flush any nasty fuel out too.

Does the "pinging" sound like detonation or ? If you can upload an audio file, that may help. Running with one engine at a time should help narrow down the pinging too.

Good luck.

[rodbolt17]

wont be the first time I ever redid the carbs AND the pump after another tech did just the carbs.

if the pump has debris in it and you rebuild the carbs guess what happens?

if the pump is failing and is feeding debris to the carbs, guess what happens?
see where I am going?
your there ,spend another 100 bucks or chase ghosts.
its a fuel pump, lives about 3 seasons or so.