91 225 runs erratically @ high RPM

Hello,

I recently bought a Mako 230 Walk Around with a 1991 Yamaha 225. The boat and motor had been sitting for perhaps 8 years. I had a competent marine mechanic go over the engine, he rebuilt the carbs, put in new fuel pumps and said the compression was good in all cylinders. She runs fine at low RPM's, but won't go over about 36-37k RPM at speed, and sort of "pulses" up and down in rev's running flat out. Fuel is clean, have checked for water, drained carbs, inspected main jets, all seems fine.

Any ideas?

Thanks!

[boats.net]

Run it on a portable gas tank to check for a fuel restriction.

Tried that, does the same thing.

No alarms. Today I totally cleaned and checked out the recently rebuilt carbs, tried running it on an alternate fuel source as well. Discovered that new fuel pumps had been installed without gaskets on engine side. Hoped that was the cause, with lack of vacuum pressure, but no. Pumping the bulb has an effect of performance, so I still believe it's fuel supply related. Totally baffled & frustrated at this point.

that would do it

That would do what?

BTW, I TOTALLY agree with "Yuck the Fankees" living in the NY area with these arrogant Fankee fans is annoying to the extreme. Luckily, they're kind of quiet lately, LOL.

the gaskets not there

You'd have thought so, but that didn't solve the problem.

Tried that, does the same thing.

Have the fuel filters been changed?

Have the fuel filters been changed?

Yes

you need to run a fuel pressure/vacuum test

The fuel pumps are brand new.

vacuum test

How does one do that? Is there a tutorial anywhere?

Thanks!

[jb123]

when you used aux tank....did you also use aux hose and ball hooked to motor filter? if you didnt...and if you have an airleak, you wont find the issue.

when running under load...see if choking helps increase power/rpms. still sounds like youre dropping a cylinder or 2 to me, whether by spark or carb.

when you used aux tank....did you also use aux hose and ball hooked to motor filter? if you didnt...and if you have an airleak, you wont find the issue.

Yes I had an aux hose & ball - same behavior. All the hoses from the motor filter to the carbs are new.

when running under load...see if choking helps increase power/rpms. still sounds like youre dropping a cylinder or 2 to me, whether by spark or carb.

This motor has an auto choke, so I don't exactly know how to do that. Also, what will that tell me?

Thanks

[Operaman]

Squeezing the bulb helps? What brand bulb do you have? Get a Yamaha bulb and fuel line assembly. If you squeeze with engine not running, idle position, does ball get hard? And if so, any leaks?

And, vacuum test is a great idea as above posted. Also, check if your bulb is collapsing when under way.

Aftermarket bulbs are junk.

200 HPDI Vibration/RPM Loss

We have 2002 200HPDI Yamaha (Z200TXRA) on our boat. Sometimes at 1000- 1500 RPMS the engine begins to vibrate. If we try to accelerate, the engine will not go above 2500 RPMS at full throttle, and it sounds noisy. We have a Yamaha long 10 micron filter in the line. I have changed it twice this season. (We've run about 15 hours total since the season began} The last time I changed the 10 micron filter was 2 trips ago. (about 5 hours & the problem recurred)

When I dump out the 10 micron filter into a clear container, no water shows up. the engine also has a water-indicating float which never rises to indicate water in the system. I also changed the fuel filter in the clear engine cannister where the water indicating float is 2 trips ago (about 5 hours).

The most perplexing aspect of this problem is that when it occurs, we can shut off the big engine and ***** with our 2001 9.9 Yamaha 4 stroke engine(which draws off a " T " valve from the same tank, but which bypasses the 10 micron filter.) After about an hour or 2 -- once we stopped for 2 hours when the problem occurred-- the engine will respond normally again. The ball does not collapse when this problem occurs.

It has been suggested to me that the Vapor Separating Filter may be the problem. Can a vVapor Seperating Filter be partially clogged & be intermittant? I've also been told that the 10 micron filter could be clogging up. (Each time I change it the problem gets better for 3-5 hours of running. Is there any way that the 10 micron filter could "recover " & allow fuel to flow again after a "rest"

If anyone can respond we'd really appreciate it.

Jack

Peep this homie: http://yamahaoutboardparts.com/showthread.php?p=27265
im about to do this to my 2000 F100 due to it not running over 2grand and being in great shape. Not sure if the filters talked about in the link pertain to you but have a read anyway.

[Wellcraft238]

I just read up on shifting cutout switches getting stuck at times and cut out cyinders.... something to think about.