1999 Johnson 225 HO Carb Starving For Gas at High Speed

[BigSmallie II]

1999 Johnson 225 HO J225HPLEEN / G04608634

Need some advise.

My boat would not idle very well....so I took it to the Johnson dealer. They rebuilt the carbs and changed the fuel pump. The boat now idles and runs very smooth.

The problem now...is when I'm at WOT.....the boat starves for gas. My friend pumped the bulb while we were running and the motor took off like a scalled dog. However, when he stopped pumping the bulb......it would start to hesitate again.
The motor works fine getting on plane and does not starve for gas.......only when operating at WOT.

I have it back at the shop that did the work......but I would like some input from the members of BBC as to what you may think the problem is

Thank you in advance for your assistance.

[lkhartwl]

did you change the BULB? if not change it asap. I have the oppisate problem starved at idle ok @ wot am changing the bulb today as that is the last thing on the fuel system I have to change other than a brand new gas tank, which has nothing to do with the delivery. you may also want if you can get to it change the check valve in the tank or pop the check out with a screwdriver those are the only 2 things that impeade the fuel flow @ either end of the spectrum. good luck, Steve

[rudetech1]

Usually when we have a restriction at the bulb or the tank, we get an audible horn/light on the guage. Check engine. The engine has a voes switch that should make contact in the event of a restriction. A weak fuel pump will not activate the switch but will starve the engine for fuel. When you pump the bulb, you take the place of the fuel pump.

[BigSmallie II]

No horns or warnings have gone off.

The motor will rev up.....then rev down.....rev up....then rev down as you drive down the lake at WOT. It's hard to hear with the wind in your face....but if you turn your head you can hear the motor rev up....then down. When your driving across the lake and the motor does this......it feels like the boat is "hitting"...or...."dragging" across a sand bar each time it revs down!
Once my friend started pumping the bulb.......the boat woke up and picked up 10 - 15 mph....on the GPS.......and I never pushed further on the hot foot!! So we know it's starving for fuel at top end. The strange thing is it will not miss a beat when getting on plane........which calls for the hot foot to the floor!

I talked to the mechanic today. He said they tired several things so far.......but everything checks out. He said that it starts to do this at about 4,000 rpm. They were waiting to hear back from a Tech.

If pumping the bulb is taking place of the VRO/Fuel pump......then wouldn't it be the fuel pump? But then......this was just replaced...brand new!! Could it be bad??
After all.....the boat never did this with the old VRO/fuel pump!

Anyone else?????

[THE WITCHDOCTOR]

If he didn't get the float drop set, it could be running out there..... he didn't change the hs jets did he?

[rudetech1]

Even a new part can have a failure. Whitchdoctor is right on the float drop, they may be off. It would account for the surging. If it was me, I'd recheck my work.Did this problem exist before the carb jobs?

[BigSmallie II]

Nope.......ran fine at high speed before the carb rebuild and the fuel pump.

I thought maybe the high speed jets may have something to do with it.....but then....why would the motor run strong when the bulb was pumped?? Wouldn't the high speed jets still only let the same amount of air/gas through?

Thanks for the help guys......the quicker I get this fixed...the better. Bass season and tournaments start next weekend!!!

[THE WITCHDOCTOR]

You are correct smallie. The only reason I mentioned it, years ago, when my motor got tore down by a dealer for rebuild, he changed the hs jets in it because he thought they were too big according to the book.... well, for a standard 225, it calls for 72d, and the ho calls for 76d....it took me a while to find it, but finally did! I still say flaot drop.....

[SEAHORSE]

Did the dealer also change out the pulse limiter that goes into the cylinder case and "blocks" any backfire that may damage the pump? A new one comes in the pump kit.

Hook up a fuel pressure gauge to the pump output and make sure it is above 5 psi at all speeds. Some systems may be as high as 12-15 psi.

Hook up a clear fuel line at the pump inlet and Tee in a vacuum gauge and run the boat.

Both tests will tell if there is a fuel delivery problem in the boat, or an output problem on the pump.

If both test OK, then it is probably the carbs, most likely float levels and/or drop adjustments.

[BigSmallie II]

Thanks everyone........looks like the "float drop" is in the lead!

I'll run this by the mechanic to see if they have checked it yet.

Thanks again for your assistance.

[THE WITCHDOCTOR]

This might be premature to say, but it is surprsing how many mechanice don't know how to set "float drop".......

[BigSmallie II]

Ok boys......I ran our posts by the mechanic. He said he tried the same things mentioned. No change.

He then put on my old VRO/Fuel pump and ran the boat again. He said it was better.......but still had the surge problem....and always started at 4,000 RPM. He said he did a slow take-off to get on plane......no problem.....until 4,000 RPMs.

When I asked about the float drop......he told me that he pulled one of the floats and said the "O" ring looked swollen and disformed...so much so that he could not put it back together. He then asked if I had put anything in my gas and/or where I got my gas.......because the "O" ring looked like it had been soaking in some kind of cleaner. I advised the only thing I put in was Shell gas.

Looks like I'm back to square one! Any more assistance would be greatly appreciated...........

[SEAHORSE]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BigSmallie II &raquo;</TD></TR><TR><TD CLASS="quote">Ok boys......Looks like I'm back to square one! Any more assistance would be greatly appreciated........... </TD></TR></TABLE>


One possibility, that I haven't seen in quite a few years, is distortion on the fuel inlet fittings on the carbs, fuel rail, and any "Tees" in the plumbing behind the air box. If the hoses were tight and someone pulled them forcefully, the plastic would stretch and restrict the ID of the fitting. The reduced inner diameter would affect the flow of fuel to the bowls. This was very common on the pre-1993 engines with different plumbing arrangements. This was also the reason some motors would ruin a piston after a few hours of running.

[BigSmallie II]

Just got a call from the mechanic..........the boat is fixed!!

Kind of a bizarre problem..........the mechanic started tearing down the carbs to inspect the float drop when he noticed that the majority of the "O" rings were all swollen. 5 out of the 6 carbs had to be rebuilt again!!! Even the small "O" rings were bad????

I have NO idea why this would happen. I have not put any additives in the gas....and have been filling up at Shell gas stations.

Has anyone heard of these rubber "O" rings going bad this quick??? The carbs were just rebuilt in late April of this year??

[rudetech1]

HMMMMM.

[THE WITCHDOCTOR]

Did he use the factory kits or sierra?

[SEAHORSE]

Did he use new kits, or just reuse the orings, gaskets, and the needles and seats?

[ChampioNman]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SEAHORSE &raquo;</TD></TR><TR><TD CLASS="quote">Did he use new kits, or just reuse the orings, gaskets, and the needles and seats?</TD></TR></TABLE>

Not much of a rebuild if he used the old stuff . Only 2 O rings and not really an O ring (really a rubber gasket) one is in the kit for the carb mounting to the throttle bodies. the one that fits the bowl isn't part of the kit. That could be the one that is the culprit. The O ring is for the carb drain screw.

[BigSmallie II]

It was more to do with the needles at the float. The tips were swollen and sticking.........so I was told.

I asked and received these parts. I did not ask for the previous set I paid for in April. These parts were from BRP.

Rudetech1............yes.......I am smelling what your cooking! I certainly hope what I think happend.....did not happen.

Thanks for all your help everyone..........I think all your posts actually got the job done...............that I originally paid for! Now twice

Chalk one up for experience!