Yamaha OX66 225 1999 update

[Bob M]

Thanks to TimC, TomS, Dale and others on this site I was able to clean the VST fliter, replace the 3 low pressure pumps, cleaned and then replaced the oxygen sensor (when cleaning didn't seem to help).

Having run the boat a little the last 2 evenings I find that initially when I run past about 4300 rpm I still get surging and loss of power. After a couple of short runs at high rpms, the next time I get on plane I can run up to 5400 rpm (tops out with motor trimmed up pretty high) with no surging or loss of power.

Anyone have any ideas why I am still having problems when I first run it up?

 

[Megabyte]

Do you run Ringfree and/or StarTron regularly, and have you performed a decarbon this season?
How about your 10 micron fuel/water separator cartridge? When was that last changed?

Sounds like you are getting there since you can now run max rpm's, but I'm thinking you might still have a (dirty) fuel issue.

 

[TomS]

Bob,

Trying my best here, but I'm no mechanic.

One thing to try the next time you are bogging down is to squeeze the primer ball and see if that has any effect.

Do you happen to have a fuel pressure gauge? It hooks up to the top of the VST tank. Would be good to see what is happening to the fuel rail pressure when its bogging down.

Also, trying to eliminate the other obvious things.. do you know if you have an anti-siphon valve installed at the fuel tank pickup? If you can, also try to see if the problem occurs with the gas fill cap off to make sure you don't have a problem with the fuel tank vent.

Are you applying throttle at the same rate for both runs? In other words are you gunning it one time and gradually increasing the other? After the initial bog-down does the problem repeat itself after that?

-- Tom

 

[Bob M]

I have not run ring free but will add some to the tank. Fuel water separator is new as are spark plugs.

I wonder if it takes a while for the oxygen sensor to get hot enough. I read that it needs to be at 600 degrees to work.

I am going to add the ringfree tonight and see if that helps.

 

[gw204]

I bet your TPS is out of whack... Others will have to chime in to tell you how to check/fix it though.

 

[John_Madison CT]

Those intermittant problems are a bear. I'd try a fuel pressure guage while running to see if you notice a drop in pressure when she surges.

 

[Bob M]

Thanks for all the responses. I ran the boat last night after adding some ringfree. It seemed to run better overall. I cruised at 4200 rpms for a few minutes before accelerating faster. It accellerated up to the max of about 5400 rpm with no problems. I ran it around for about an hour ,sometimes idling, sometimes cruising at 4200 and then accelerating to top speed. Did not experience any problems.

I think Dale mentioned decarbing the motor. Would this be the same thing as what the ringfree bottle calls a shock treatment of extra ringfree?

 

[Megabyte]

I think Dale mentioned decarbing the motor. Would this be the same thing as what the ringfree bottle calls a shock treatment of extra ringfree?

Yes. The shock treatment is 1 ounce of Ringfree per gallon of fuel, and the maintenance treatment is 1 ounce per 10 gallons of fuel.
If you do a search here, you will see several threads that explain the process.

If you are running better already, upping the dose to get her clean will not hurt anything, especially if you are low on fuel. You really can't 'overdose' on Ringfree if you were to put in, say 3 ounces per gallon.

Once you have the motor cleaned out and running well, keep up the maintenance dose and you should be good to go.

I put both Ringfree and StarTron in my tank at the 1 ounce per 10 gallons rate when I refuel, and my 1997 motor has never run better than it does right now.
30 kts at 5000 rpm with 5 people aboard and 1/2 a tank of fuel just last weekend. :wink:

There are folks here who are not a fan of fuel additives, but the system that I use (Ringfree and StarTron) has produced good results, so I'm sticking with it.

 

[TomS]

"Dunk" is the king of de-carb, here is his method using a product called SeaFoam:

http://outdoorsbest.zeroforum.com/zerothread?id=2589

IMHO, Ring Free is way too expensive to use for decarb. Get some Seafoam at any auto parts store.

I just did mine the other night. In the past, I've simply done a de-carb while changing the racor filter.. Fill up the new racor filter 3/4 fill of seafoam, 1/4 of gas and let it run for a while, then sit for 10-15 minutes and run again.

The other night I knew I was going to be doing some other maintenance, so I used "Deep Creep" which is the spray version of Seafoam, and I used it just like I was fogging the motor. Took the air cover off and sprayed the Deep Creep into each air intake one cylinder at a time, while the engine was running. I probably used about 1/3-1/2 of a can. Then let it sit for a while and then ran it to clear all the smoke.

-- Tom

 

[Megabyte]

IMHO, Ring Free is way too expensive to use for decarb. Get some Seafoam at any auto parts store.

I just did mine the other night. In the past, I've simply done a de-carb while changing the racor filter.. Fill up the new racor filter 3/4 fill of seafoam, 1/4 of gas and let it run for a while, then sit for 10-15 minutes and run again.

Great tip putting Seafoam in the Racor! :wink:

 

[Bob M]

Thanks Capt. Kevin and Tom,

I'll take your advice. I can't believe I have been running this engine all these years without knowing to use ringfree or to decarbon the engine.

Once again this site has proven to be a great resource!

 

[TimC2520]

Good job Bob, sorry I was away in the OBX all week away from the computer.
Congrats on getting her up and running smoothly.