Low power/idle RPM- running rough

[Capt. Lowtide]

Great forum here, I lurk often and learn plenty...THANKS!

V150 TLRZ- 970 hours, saltwater engine

Picked up the boat from my regular mechanic last week after replacing water pump, gear case seals (blew out upper seal at 12 psi when tested), spark plugs, oil reservoir filter, plastic fuel filter housing on engine and ran engine tuner. I sent the motor in for a water pump kit only and was very surprised that all this other work was performed without my authorization. Visited with owner about the additional $600 and he adjusted some labor and conveyed to me that my business there is no longer needed.

Now to my current issues:

Launched boat, started and warmed engine with neutral start at 1000 rpm's for several minutes and then throttled up slowly onto plane for 200-yards before going to WOT.

Within 30 seconds the engine started losing power, boat came off of plane and when I throttled back the engine died and would not start. Smelled of fuel so I assumed it was flooded due to faulty fuel pump diaphragm (I seem to replace one pump or the other every 150 hours.)

Trimmed engine up to drain carbs and let rest for several minutes. Tried to start again and wouldn't, advanced neutral start to wide open throttle (previously this was the only way to get running when stranded from faulty fuel pump.) Once running the engine would only reach 3000 rpms under load, so I limped back at 1200 rpms.

Tied boat up, acquired tools and loosened bolts holding each pump and primed bulb- fuel squirted out of hoses connected to filter housing under cowling (plastic ties were not put back on and housing was not mounted securely.) Once back together properly the system was now holding prime and no leaks from fuel pumps.

Engine was hard to start and idling rough at 400-500 rpms, had to advance neutral start to 1000 rpms to keep engine running.

Removed Yamaha spin on fuel filter, dumped in clean bucket to check fuel, removed/checked new plugs, checked fuel pumps again and no leaks.

With the recent mishap at the mechanic shop I do not feel trusting in their services or welcome to spend money there. I am now faced with 3-week turn around at any reputable dealers in my area. I use this boat/motor to make a living and need it operable by this Thursday.

After recent repairs I am now low on funds, any and all suggestions for diagnosis/repair would be greatly appreciated.

[99yam40]

My guess would be the carbs need to be pulled and cleaned and then everything adjusted to book

[Capt. Lowtide]

My guess would be the carbs need to be pulled and cleaned and then everything adjusted to book

99yam40, you are spot on!

I drained the carb bowls and found gritty stuff and milky fuel. Pumped 22 gallons from the tank for disposal and now looking for good instructions for the carb rebuilds.

I thought I was immune to the phase separation situation. I treated the fuel heavily with Seafoam (1oz per gallon) last fill up 11-weeks back and burned 15 gallons 3 weeks ago without a hiccup.

SIDE NOTE: Today I put a pint of fresh from the pump 87 octane in an open top pickle jar and within 3-hours had about one tablespoon of water in the bottom. *** what an eye opener!

[Atchafalaya_man]

Fuel separation

An independent mechanic shop that has been in business for 30 plus years says that over 50% of their business now is fuel related.

Therefore, I drive miles to find ethanol free fuel for my boats. I easily notice a difference in the fuel-mileage and performance of my truck as well.

Among other places, one can find ethanol free fuel stations at the following web site. I make it a point to go into the station(s) EACH time I buy fuel and tell the owner or manager that I came to them from far away because they sell non-alcohol fuel.

Ethanol-free gas stations in the U.S. and Canada

[rodbolt17]

ya simply need an alternator.

[Capt. Lowtide]

Tore down the carbs and cleaned them all up....same issues



looking into testing the stator now

[Tucker]

Are you running on a remote tank with good fuel? Still thing fouled fuel is your problem.

[Capt. Lowtide]

Are you running on a remote tank with good fuel? Still thing fouled fuel is your problem.

First of all, thank you all for offering assistance and questioning of the situation.

Before I tore down the carbs I ran a pint of Seafoam in a gallon of gas intermittently from a remote tank. I hooked up inline infront of primer bulb while bypassing the fuel/water separator, in hopes this would clear any obstructions and gunk from line and through the fuel pumps on engine.

After the carb tear down the engine was run from the same tank as the Seafoam test. I pulled spark plugs and found that the plugs on the starboard side are clean and smell of gas. Initially when this problem occurred on the water I pulled the plugs and they were equally oiled, this made me believe that it was most likely fuel and not electrical.

Borrowed a boat to run trips the last couple of days and haven't had a chance to get back to the engine. I believe there is no spark on the starboard side, will be checking today.

This is starting to worry me, already spent $900 in the last two weeks on the engine. That amount and whatever additional will be spent to get it running correctly would have made a few payments on a new F150

[Capt. Lowtide]

Ran the engine this morning and pulled spark plug boots to check for adequate spark. With all three starboard side cylinders and the bottom port side cylinder boots pulled the engine did not change in running operation. I assume that they are not firing. I'm really surprised this engine is running on two cylinders!

Another thing I noticed is that the waxy insulation on the Pulser Coil looks to be melted and sagging from the coils.


Any suggestions or comments?

[Tucker]

Comments only, this is over my head. I know if you mess with the battery switches when running you can mess up a coil but I don't know if it's the stator or pulser coil, or both. Need the rodbolt to sound off on this.

[99yam40]

pulling plug wires off while motor is running or even while turning over can cause the voltage to jump internally on the coils when it has no other place to jump to and short them out. That is why everyone says to use a spark tester adjusted to the proper gap.
that and bad coils can cause feedback and spikes into the other charging parts and cause them to go out also, but I do not thing it would effect the pulsar coils though.
Sounds like that pulsar was overheated to make it 's insulation to run.

It is always best to use the proper test equipment and test things to see what is happening like the manuals says. the electrical is easy to eliminate by testing and then it just leaves the fuel system

[Capt. Lowtide]

pulling plug wires off while motor is running or even while turning over can cause the voltage to jump internally on the coils when it has no other place to jump to and short them out. That is why everyone says to use a spark tester adjusted to the proper gap.
that and bad coils can cause feedback and spikes into the other charging parts and cause them to go out also, but I do not thing it would effect the pulsar coils though.
Sounds like that pulsar was overheated to make it 's insulation to run.

It is always best to use the proper test equipment and test things to see what is happening like the manuals says. the electrical is easy to eliminate by testing and then it just leaves the fuel system

What would overheat the Pulsar? I first noticed the gooey insulation while on the water, but didn't think much of it.

After re-reading my last post, I see now that my ignorance is really shining through. I pulled each plug boot individually and the only two that made any difference in the engines operation were the top plugs on the port side. I "assumed" that this would mean that the engine is running on those two cylinders only.

######off to purchase a spark tester

[Capt. Lowtide]

ya simply need an alternator.

I've been curious as to why you diagnosed the alternator/stator first?

[99yam40]

It was a web thing about some guy wanting a tech to replace his car alternator to fix his problems without trouble shooting and saying it would fix the problem he had. don't worry about it. Rod was just being funny

[rodbolt17]

an inside joke.
once you buy the service manual and quit splatter gunning I may add advice.
the pulser coils are not mounted on the stator assy and cannot be seen until the flywheel is removed.
for spark triggering there are 2 pulser coils that control 1&4 and 3&6.
2&5 are synthesized based on crankshaft position sensor input.
lose the CPS and you lose spark on 2 cylinders, lose a pulser and you lose spark on 4 cylinders as the ECU will go into default.
ya simply are wasting time pulling plug wires.
for capacitor(spark generation) there are two charge coils, one high speed and one low speed.
its a dirt simple setup.
but ya have to have some equipment, some knowledge of how and why it works and a manual of some kind.