1991 ProV200 bogging down

[dilb1229]

I'm back after 4 years with same problem. You can search and find my original post from 2013 (proV200 or dilb1229).

1991 ProV200 2-stroke bogs immediately when giving it throttle. Will barely climb to 2000 rpm.

A little history, more at old post. Problems have always been fuel delivery related. Fuel (old), fuel pump (torn diaphragm), and carburetors (always the carburetors).

Last year, same problem. Cleaned the carburetors, fresh fuel (or at least 60/40 fresh/old) with Stabil. Ran great several weeks in a row. Went to an event to teach kids to ski. Ran great on Day 1. Probably burned 10 gallons or so. On Day 2, it ran but with reduced power. Enough to pull the kids, but that was about it. Probably burned another 7-8 gallons. Day 3, would start but that was about it. Bogged down immediately when given throttle.

Pulled the water separating fuel filter - no water at all. Disgusted, put back on trailer and it has pretty much sat untouched until now (9-10 months). Event is coming up again in 2 months.

I have drained the tank of all but a couple of gallons of the remaining fuel (still no water present), added 'Mechanic in a Bottle', 5 gallons of fresh 91 octane. More 'Mechanic in a Bottle'. Ran it on the hose for about 15 minutes at ~1500 rpm. Did this 3 times over about a week, supposedly to let 'Mechanic in a Bottle' do it's thing. No overheat, starts, runs and revs easily with no load, in neutral or in gear. Took it to the lake. Harder to start, tended to die when put in gear to back off trailer. Finally off the trailer, bogs immediately when given throttle.

Back home, removed the carbs, removed all jets and passageway screws, soaked overnight in Berryman Chem-Dip carb cleaner, rinsed in hot soapy water, rinsed again in hot water, dried and blew passageways with compressed air, lightly coated with silicone spray and blown through passageways. Re-assembled (did these one at a time and sketched diagram so I put the jets back in the same places), idle screws set to 1-3/8 turns, float level 5/8 inch. (Side note - carbs looked clean, no corrosion, no plugged jets or other holes, idle screws and floats to spec.)

Took to the lake. Motor started easily (maybe easiest ever cold), idle is maybe a little low (600 vs 700). Backed off the trailer. Gave it throttle, bogged immediately.

Came home, put clear tubing on fuel pump exit and plugged line to carb. Cranked motor and fuel pumped out. Did this to both fuel pumps so I don't think it is the fuel pumps. Couldn't find any indication of fuel line leak or air leak. Primer bulb acted like it's check valve was leaking. Will replace that, but don't see that it would cause my problem. Could it? Also will replace the fuel/water filter.

It always seems to be the carburetors and I'm still somewhat convinced that's where the problem lies, but I'm truly baffled on how it ran great on Day 1, fair on Day 2 and pretty much not at all on Day 3, with nothing done to it between those days.

Floats? Needle valves? Can see it running poorly if some aren't right, but all (or most) of them? Wouldn't there be some indication with no load? I have the old floats and needle valves from previous re-build. Worth swapping them out?

Am I setting the floats wrong? Same way as when it ran well. Upside down, measuring from the surface of the gasket to the top edge of the float as you are looking at it. 5/8 inch.

Thanks for looking and appreciate any help.

Steve

[99yam40]

compression, spark, timing, and fuel to air ratio

check what you can and then play with the others

[TownsendsFJR1300]

I gather this is your engine (Counter rotation but it was only with with a carb breakdown)?:

1991 P200TLRP Yamaha Outboard CARBURETOR Diagram and Parts

First, I would simply drain the bowls (drain screws) and catch what comes out. You can tell by the look, smell of the fuel and for ANY DEBRIS coming out. Watch for any separation. Use the primer bulb to flush carbs too.

When you drained the tanks, did you use the primer bulb (disconnected from the engine) and suck the tank dry that way?

If the tank was not fully drained (even to add some fresh fuel, drain again-use in the car, if it's clean) and known to be clean, you very likely introduced more tank crap into the carbs...

Once the above is done, I would suggest using a different stabilizer "Gas Shok" or K100, ALL the time. Not just once in awhile as ethanol fuel goes bad in as quickly as a month. If possible, don't use ethanol fuel. It's simply NOT worth the headache to save some bucks..

Not using a GOOD stabilizer WILL clog carbs very quickly...I've had them clog an old v4, 140 Looper in a week with no stabilizer (years ago).

IME, I would strongly suggest running a shock treatment (2 oz / 1 gallon) of Yamaha's "Ring Free". Six gallons (if a separate tank is available), if not, the appropriate amount for what's in your tank.

The Ring Free cleans the Fuel System as well as the top end. The K100, if there's water in the system, will suspend it and you'll eventually burn it off...

I personally run RF and K100 in the boat with NON-ethanol. I have gotten well over 2 years without the fuel going bad, no bad smell, looks like it was just pumped, no water visible.

There are no downsides to using the shock amount (except to your wallet), but I personally use RF in every gas machine I own.

RF: https://www.shopyamaha.com/product/d...?b=Search&d=34

Gas Shok: Gas-Shok Plus Gasoline Fuel Treatment • USA Fuel Service

K100 (3rd video): Demonstration | Fuel Additive | K-100

I suspect, right now, the carbs are leaning out. Should you close the choke butterflys part way when the issue occurs, I suspect the engine will pick up RPM's (to a point), much more than your getting now..

[zenoahphobic]

Seems you are looking for a needle in a haystack.
I'm nitpicking but sometimes we can be a victim of our own doing.
I therefore worry about your final hot water wash, water being slower to dry and being pearled by hydrocarbons can remain somewhere; and the use of silicon spray as it to does not readily wash out with fuel.
Just a thought to keep in mind.

[dilb1229]

Question (it may or may not pertain to my problem): If everything else is OK and the only problem is fuel pump related, wouldn't you get an initial surge of acceleration followed by it bogging down as opposed to it bogging down immediately? Seems to me that once it starts and you are idling, that would mean you have fuel in the bowls Wouldn't that be enough to initially accelerate? Am I missing something here? It wouldn't be the first time.

Also, there are 2 fuel pumps with both outputs jointly feeding the 3 carburetors. Wouldn't both have to be bad?

Steve

[TownsendsFJR1300]

Yamaha apparently wanted two fuel pumps to keep up with the demand.

If one pump is bad, your ONLY getting half the fuel needed. Carbs can't deliver fuel it doesn't have when called upon..

Is there enough fuel in the carbs, idling, seems your getting enough.

An engine under load is WAY different(needs more fuel, properly delivered), than just revving on muffs..

[dilb1229]

Update:
Removed carbs and checked fuel in bowls. No debris or water found. Re-cleaned (dipped) the carbs 30-45 minutes, this time rinsed in bottled water, then blown dry with compressed air. Checked idle screw and float settings. Tweaked 2 floats but they were within spec. Replaced check valve (in motor between small screen filter and fuel pumps), new primer bulb, and new water/fuel filter. No debris or water in old filter.
Following is done on muffs and at idle speed. Put vacuum gauge in fuel line between screen filter and new check valve. Registered 4 inches. Closed a fuel line cut-off valve. Gauge reading moved up. Re-opened valve when it reached 6 inches, reading dropped back to 4 inches. Moved gauge to between primer bulb and motor. Still 4 inches. Moved gauge to between primer bulb and water/fuel filter. Still 4 inches. Moved gauge to between filter and cut-off valve. Vacuum dropped a little to just above 3 inches. Moved gauge to tank. Still about 3 inches. No change whether fuel cap in on or off (indicating tank vent is OK). Blew compressed air into tank (fuel cap removed). Re-connected vacuum gauge. Still about 3 inches. In case it matters, boat is a 20-ft ski boat with fuel tank in bow. Cut-off valve is 3/4 of the way back to the stern.
Hope to drop it in the water in the next few days to see if anything helped. Will post results.
Steve

[TownsendsFJR1300]

Update:
Removed carbs and checked fuel in bowls. No debris or water found. Re-cleaned (dipped) the carbs 30-45 minutes, this time rinsed in bottled water, then blown dry with compressed air. C

Did you pull the JETS OUT AND INSPECT?.

[99yam40]

running a motor that is leaning out a cylinder or more can hurt those cylinders/ motor.
pulling the kids for a period of time with a sick motor is not good on the motor.

start from scratch
make sure all cylinders have good compression,
look at the plugs when you pull them duing compression check to see what they look like.
make sure spark and timing stay in spec when problem shows up.
if all that is Ok then deal with fuel.

if you did not suck the tank dry and clean it, there could be water or trash left in the tank.

the pick up tube will not get all of it out of tank

[amahaork]

Why don't you try regular gasoline without all additives. Use separate fuel tank.

[TownsendsFJR1300]

Why don't you try regular gasoline without all additives. Use separate fuel tank.

I didn't read anywhere that he used ANY additives...

Did I miss something?

[99yam40]

nope you did not miss anything, he just likes to bring stuff from other threads up in others

[TownsendsFJR1300]

nope you did not miss anything, he just likes to bring stuff from other threads up in others

Yep, I know that. "My snake oils". (I was trying to be nice)...
Guess it annoys him like several other members..

amahaork's fix: "a separate tank" (which wouldn't hurt but ISN'T the issue).


.

[dilb1229]

Just back from the lake. Still no power, but it was a little better. Got 2900 rpm, about double what it was doing before.

Yesterday got a loaner compression tester from AutoZone. Registered 90 psi across all 6 cylinders.

Observations from this morning.

Idle rpm was about 200 lower in the lake as opposed to on the muffs. 500 vs 700 (spec). This was after letting it warm up in the water, on the trailer.

While idling along, about 1100 rpm, checked primer bulb. Still firm. Since I'm alone in the boat, can't do much checking while underway.

While in reverse, motor revs easily to 3300 (higher than in forward), without bogging. I read that this is not uncommon, having to do with prop pitch in reverse has less load, so more similar to running on the muffs. But it does seem to pull pretty strongly in reverse.

I can put the vacuum gauge back between primer bulb and motor and take to the lake to see if anything changes with WOT and under load, like a collapsing fuel line (unlikely as these lines are pretty stout).

I can (and will) clean the carbs yet a 3rd time in as many weeks. First time, removed all jets and screws that plug passageways. Second time just removed the screws. The holes in the main jets are relatively large and can see no signs of blockage or corrosion. Likewise, the air bleed jets (one has large hole, other small), can easily see through them with no signs of blockage or corrosion. Likewise the main nozzle. All the holes drilled in the carburetor casting that I can see are likewise clear.

Floats and needle valves show no signs of wear, but I can change them out with an older set from a rebuild years ago. Shaking carbs, I can hear them move, but can't necessarily tell if it is just one or both. No reason to think they are sticking though.

Will check fuel/water filter, but will bet there is no water or debris to be found.

Will also get some better gas shock treatment.

Any reason to think the fuel pumps are not pumping as well as they should? Both are pumping fuel, but is it possible that the diaphragms have stiffened and while they are working, they are not working as well as they should? I have 4 other fuel pumps that 'should' be good. Have opened them up and see no tears in the diaphragms.

Steve

[99yam40]

you bypass the pumps by using the primer bulb and fill up the float bowls.
motor should take off strong but run out of fuel if the pumps do not keep up with the demand of higher RPMs.

As always you need good compression and good spark on all cylinders, along with spark at the correct time.
check timing to see if it is in spec at idle and advances when RPM goes up.

Timing lights are easy to use, but at WOT on the water it can be dangerous to be playing with the motor on the back of the boat
If not advancing the power will be off.

90 PSI is not very good, I would expect more, but it may be the gauge.

at least they are all even

never hurts to test or inspect the pumps