1991 225TXRP: screams to 4800 rpms and then backs off to 4000'ish

[carboncow]

We are patiently waiting for coil to come in as we think we may have a funky one. Have not done a full timing light test yet but the one plug loads up a bit.

The engine screams out of the hole up to about 4800rpm and then there is a loss of power and it runs pretty good about 4000-4200rpm. My buddy on this project says it reminds him of when he's had bad coils on previous engines...and says that one bad coil spoils the party pretty hard when it comes to outboards.

What else would you guys be checking?

We've got the carb sensor dialed in at 0.5v
linkages are tight
Fuel flow seems fine with new lines, filter housing, filters
Figured if CDI trigger was not producing enough voltage we'd see more violent issues with running.

What other fancy pants electromagnetic magic should we concern or does this sound like a coil issue to you?

[rodbolt17]

quit chasing ghosts.
don't involve peter cottontail.
go fix your fuel issue.

QUIT thinking ANTYHING YOU THOUGHT YOU MIGHT KNOW CONCERNING AUTOS.

next time you take granny's grocery getter chebby into the dealership.
tell the tech it runs good at 4500 RPM in high gear for about 10 min then falls on its face.

watch the stupid look .

electronic failure on that motor is incredibly rare.

does your buddy know the difference between a single oil filled coil and 6 dry coils

no . your issues do not sound electrical.

quick test, with the air box off, when it falls off, spray 50/1 premix down the carbs.

[carboncow]

OK...

Yes I don't like to chase ghosts either but most of the "testing" we are getting suggested involves timing guns strapped to engines doing 40mph on the lake. Yes troubleshooting with cars flying down the freeway with the hood open is not what I"m used too...but it seems pretty common in the outboard world!

So you think electrical is not way to go and you are leaning toward fuel? Can you at least tip your hand a bit more on WHAT we should be considering then?

What would be the causes of fuel issues at the higher RPM. Are we talking flow, oil injection, simple adjustment? What makes it want to go and then 1.5 seconds in settle down to 4K. Why makes one plug oiled up more then others except spark issues? What magic/science is there in carbs and flow that I have no experience with?

We have tried bypassing the new filter just to see if it's a flow issue restriction there with no success.

If you are suggesting we go down a patch let me know where you think it may lean...try not to enjoy us floundering!

EDIT: I should add that I never said it runs well for any length of time. It screams from the holeshot up 5000+ RPM and then settles into 4000+ pretty quickly.

[rodbolt17]

at rapid acceleration guess whattttt??????
those two A and B solinoids open up a bit and aid in making the intake a bit richer.
once it quits and then one carb starts leaning out,most likely the one that the plug is oiling up on, it falls flat.
oil by itself doesn't burn well.
yet its injected regaurdless of the amount of fuel being delivered via the main jet and emulsion tube.

your describing a classic lack of fuel in the fuel bowl.
be it from weak fuel pumps, air leaks on the pump suction side, restriction on the pump suction side, I cant say.
but your not describing a loss of an ign coil.

think of your engine as six little motors that share a common crank.
your carbs as six little carbs that share 3 bodies.
cause that's about how it works.

if you care two you can make up a 6 lead pigtail about 6ft long and hook all six ends to each ign coil primary and the other end inside the hull. then using your DVA meter simply monitor peak ign coil primary voltage.
you could also beg borrow buy or steal test wheel YB1626.
40 MPH across the lake?????
try it at 72MPH hanging off the back.
here is where that test wheel actually comes in handy.
its a known load that the engine spins up against and the engineers calculated THAT 225TLRS should spin YB1626 at 5450-5650 RPM.
if it cant, motors broke.
you already know which cyl is not running correctly, that's the one I would spray premix down the carb throat at the failure RPM and load.

[carboncow]

There is some good info there...lots to sort out and quite a few directions. We met one Yamaha tech that knows mechanicals pretty good. After listening to you I'm have tempted to toss this at him then...you are making my head sping.

We have thought the lack of fuel at times and ever removed the filter (mentioned before) from the equation. I see a small portable tank test in our future.

I've been reading up on the DIY primary coil tester.

So with all this info to test...which we will start tomorrow night. I'm still not getting what "one cylinder" loading up with oil can mean if the coil is not to blame. We know we got consistant and good (125+ lbs) on each cylinder. Since you used the 6 little motor analogy why wouldn't a couple of cylinders lean out and not just one?

[exeter27]

carboncow, re-read rodbolt's information until it makes sense; he's done this a long time, has helped a LOT of folks and knows what he's talking about.

The key takeaway is the the carb bowl is likely running low on fuel. At that point, that cylinder no longer drives the engine and actually becomes a drag, dropping your RPMs. You need to figure out why it becomes fuel starved.

But, to prove it, do what rodbolt says and spray some pre-mix into that cylinder when the problem occurs. If it clears up, you know you have a fuel issue. If not, then you might consider electrical. I've seen electrical components get funky when heating up - but your description doesn't fit that.

I'm betting on fuel. Good luck

[carboncow]

EX,

Thanks. I find RB great...intense info and delivery...keeps you on your toes but having you clarify is a saving grace. Almost to much info on his last post has he had me thinking fuel and then started talking electrical again.

We we had a chance to go over the engine today in the garage and I see I got a bit of misinformation from my buddy...and it falls RB's explanation and fuel I think.

See the two attached photos of plugs that were new and run in the engine for about an hour...no more then two. The bottom plug is clean, middle is getting dirty and the top is very oily. The same behavior on both sides...so this (from what I'm understanding) shows that fuel is thin and thus oil is heavy.

It's worth mentioning (I found this out today) that the engine was struggling to hold idle after running and warm...going to guess this is due to the plugs being oiled up...or is there another symptom/theory to the bigger issue?

Now I'll try the 50/1 spray mix technique this week when we can get it back on the water but I wanted to run a few other things past you guys. This engine is going a recently restored boat and we had done the following...

1. Pressure washed and cleaned gas tank
2. New fuel lines all the say to the pumps
3. Pickup tube screen cleaned. We don't think the tube has a check valve
4. New fuel filter housing and spin on filters (changed twice in 10 gallons)
5. New primer bulb
6. New filter on engine
7. New check valve on engine
8. Two new fuel pumps
9. Carbs rebuilt by us (all 3)

This was not all done to solve the issue but just doing the right thing bring a old engine and boat back to life.

We've actually removed the spin on fuel filter from the equation for testing as we suspected some odd behavior before but this but removal has not solved the issue.

With all this info what would you do next and or suspect if the 50/1 spray mix proves an issue. Would you worry about pick up tube, those new fuel pumps, would you suspect check valve or bulb...or should be be concerned and/or tweaking the carbs?

I have an inline pressure gauge coming in the mail tomorrow...how can we best use this to determine fuel flow issues?

Also...let's talk about the enrichment mechanism. Should that manual switch be down or up? Should this mechanism be removed, cleaned and oil lines checked and reinstalled...is there anything this item can be doing to mess with the system or do we simply have low fuel flow issues?

Every post helps us understand the big picture so I appreciate everyone commenting and hanging in there while the logic and understanding comes to us more every day.

[rodbolt17]

do you realize in about 1/3 the time we have been posting and you have been rambling all over, you could have worked a side job at walmart and used the money to have the boat fixed and ready to enjoy?

your buddy and you may know how to hotrod,kinda, an old chebby.
take this thing to a REAL TRAINED tech.
BEFORE you pop a piston.

[ausnoelm]

I think you should buy a genuine service manual, take heed of anything Rodbolt says, and stop jumping from place to place, you need to trouble shoot step by step, not look at plugs, enrichment levers, spark, coils.....

[carboncow]

***...I don't think either of the last two posts add anything to answer my inquiry. Sorry if you feel I'm wasting your time but some of us have time, enjoy figuring things out don't believe in the "take it to tech" is always the answer. As a matter of fact our goal is to avoid pros and do this ourselves.

If possible look at the last questions and answer what systems would you consider if our next test proves a low fuel pressure issue so we can know how to proceed with our limited test time on the lake.

I've moderated and helped on several forums for technical things like computers, Volvos, Saabs, Porsche, etc and those on the boards have no trouble answering questions and helping people get educated with out telling them to "go to the dealer" and we are hardly jumping around. We first thought it was a spark issue and now are leaning toward gas...big deal...you have to start somewhere!

The only thing negative that has been about working on this motor is how people help one minute an get opinionated in the next and cannot focus on concise answers on what to expect is most likely causing the failure at hand.

Aussie...we are jumping around on topics as we are trying to learn the system. We have the Seloc and it leaves some gaps while the official Yamaha is not been sourced for such an old engine (and Yamaha doesn't have it...we've asked).

See the issue with outboards is they need to be under load to test so many of the items discussed and we don't have access to a high speed lake where we work on the boat and we are two hours from Lake Erie which will be the boats final home with our Tiara and two jet skis (all of which I also maintain). The two techs in this area who have been somewhat helpful don't like large engines as they cannot run on their local lakes (HP limits) and one flat out says he sucks at electrical.

So see guys...we are here to learn. We are not going to grenade an engine by asking good questions and getting good answers and since you think the engine is a dinosaur then why not try. If we didn't have the intellect, resources and desire we'd take it to tech...but that is not our goal...yet.

If possible look at the last questions and answer what systems would you consider if our next test proves a low fuel pressure issue so we can know how to proceed with our limited test time on the lake.

[ausnoelm]

Not meaning any disrespect at all, but Rodbolt is the Yamaha guru, and trouble shooting needs to be done in steps, methodicaly and precisely, a Seloc manual is next to useless, (as you have found out)

[rodbolt17]

the seloc skips about to much and the Yamaha manual is for a trained tech and offers NO theory on how or why that part works with the others.
the original TPS had some issues with flat spots.
you should monitor the tps voltage at all RPM ranges.

call around, find a shop that has test wheel YB1626.
then all WOT testing can be on at the ramp with the boat on the trailer.
you can monitor CPS and CDI outputs from the helm by making leads.
do you actually have a DVA meter?
that engine uses 2 fuel pumps and 1 enrichment pump.
that top pump is for the enrichment system and draws fruel from the top carb.

not trying to bust your chops, concerned you may destroy something while splattergunning it.
that system hasn't been used since 1993 and then only on the 225.
not a lot of techs got to play with them.
in 93 I was still active duty navy as a CIWS technician.
I worked on gray boats not play boats.

but there were enough about that we got to play with them before they all corroded away.

[carboncow]

We are going for a boat ride tonight and will be doing the 50/1 squirt in the carbs under load with the fuel system on a remote tank, no filter and no check valve. Will report back with results and see where to go next...maybe a tech with a YB1626.

No it appears all our meters that have peak voltage are digital and I think you said the buffer gives poor readings...not analog with peak. I see you can buy adapter for such needs for a digital multimeter.

[99yam40]

Good/expensive Fluke meters that have the peak hold will not cut it on these systems. I know I tried.

Have to get a meter made for these ignition systems or get a DVA adapter for your regular meter

[rodbolt17]

fluke, last I looked, does not offer a PEAK reading meter.
true RMS is roughly 70% of peak.
its also called working voltage DC.
its also why real shops bill at 80+/hr.
this equipment and training aint cheap.