1999 OX66 surging and lost RPM's

[Captain Ken]

Recently bought a boat with twin 225 Yamaha's. Upon pciking up the boat the port tank ran out of gas (indication wasn't working). Have owned the boat for about a month and all was well until about two weeks ago when the port engine started surgung, RPM's fluctuating by 200-400 RPM. Just recently the WOT RPM on the same motor wouldn't go above 3400 RPM. Did some research on this site and have done the following:

1. Changed the fuel filter/water seperator.
2. Replaced the engine mounted fuel filter.
3. Cleaned VST filter (compartment and filter were clean)
4. Changed all three LP fuel pumps.
5. Cleaned oxygen sensor.

After all the above, the WOT rpm's are at 3900-4000.

The next step? Check the HP fuel pump? Could the injectors be the issue?

Rodbolt, your advise would eb appreciated.

 

[MnRiverman]

Re: 1999 OX66 surging and lost RPM's

I had a similar problem with SX 250. After doing the same as you have done, I changed the plugs. WOT RPM problem was solved.
Tom

 

[Captain Ken]

Re: 1999 OX66 surging and lost RPM's

The plugs were actually changed prior to all of this occurring, soon after I bought the boat.

 

[john mc]

Re: 1999 OX66 surging and lost RPM's

Hello captain,
I do have the same problem on my 200hp 1999 OX 66, starboard. I have taken the same actions. Were you able to pinpoint the problem?
Thanks
JP

Recently bought a boat with twin 225 Yamaha's. Upon pciking up the boat the port tank ran out of gas (indication wasn't working). Have owned the boat for about a month and all was well until about two weeks ago when the port engine started surgung, RPM's fluctuating by 200-400 RPM. Just recently the WOT RPM on the same motor wouldn't go above 3400 RPM. Did some research on this site and have done the following:

1. Changed the fuel filter/water seperator.
2. Replaced the engine mounted fuel filter.
3. Cleaned VST filter (compartment and filter were clean)
4. Changed all three LP fuel pumps.
5. Cleaned oxygen sensor.

After all the above, the WOT rpm's are at 3900-4000.

The next step? Check the HP fuel pump? Could the injectors be the issue?

Rodbolt, your advise would eb appreciated.

 

[rodbolt]

Re: 1999 OX66 surging and lost RPM's

your on the right track.
do a compression test,spark test then finnish repairing the fuel system.
you will need a EFI fuel pressure guage and a vacum guage.

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

Is the fuel bowl on the engine mounted fuel filter supposed to be full at all times? Mine is only about 2/3 full. I can pump it up to full with primer bulb but it will fall to about 2/3 full after running for a minute or two. It seems to me that this bowl should be full at all times, especially when running. My engine is 2002 model 150 HP OX 66 FI

 

[rodbolt]

Re: 1999 OX66 surging and lost RPM's

as the filter cup is on the suction side its normal to see it half full when running.
but almost any surging problem on OX66 will normally be a fuel system issue.

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

My problems started with surging. After much research and reading many forums, I Sea Foamed engine, I changed all VST filters, LP pumps, gaskets, needle valve, Water seperator, engine mounted Fuel Filter, replaced plugs, cleaned O2 tested O2, ( I think it is working according to test procedure), checked Thermostats, checked spark on all cylinders, checked compression, , checked HP fuel pressure, 35 PSI.

The surging is gone but now I dont have any torque, no top end power, and hole shot sucks.
My tach does not work so i cannot provide RPM's. I know you dont like to reference speed but, Boat used to run about 36 knots, now only runs about 27 knots. Engine starts easy, idles fine (maybe a little rough). But no real power. I am at wits end.

You can read all of my step by step work here

http://www.charlestonfishing.com/forum/topic.asp?TOPIC_ID=65419

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

I did not have any power issues until after I Sea Foamed and changed the LP pumps and VST filters. Even when engine was surging, it still had normal power when not surging.

 

[rodbolt]

Re: 1999 OX66 surging and lost RPM's

well last step would be to send the injectors to flgship for cleaning ,testing and injector filter replacement.

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

Thanks Rodbolt.

Agreed that the FI's almost certainly need attention.

Did you have a chance to look at the link I provided?

My curiosity keeps asking me why I am going through so much fuel if the problem is fuel related. The engine acts as though it is not getting enough fuel as far as performance but it is going thrugh fuel like a fire hose. I noticed last night that my fuel primer bulb is possibly losing prime.
Last week when I was doing Sea Foam procedure, I disconnected fuel line on secondary or engine side of primer bulb. To do this, I had to cut a tie wrap (cable tie) that kept it supported to the control cables. I loosened the hose clamp and lowered the fuel line into a gallon gas can that was mixed 50/50 or less with Sea Foam. When I was done, I put the fuel line back onto primer bulb and secured with hose clamp.

I did not re-tie the fuel line to the control cables but rather allowed the bulb and fuel line to "dangle" or sit on the floor of the boat (the transom well)

I had never pumped the bulb before.

After removing the fuel filter (Engine mounted) I simply turned the key and allowed VST FI Pump to prime. ( I think this is the noise I hear when I turn the key) The motor started fine and the fuel bowl filled. No problem.

Remember, I had not tied the fuel line back up to control cables. I had not noticed before but after changing VST filters, I used primer bulb to fill the VST tank. I could actually hear a noise coming from fuel tank. I assumed this was the pressure building in the tank or the actual draw of fuel in the tank.

Last night, I found myself wondering about the fuel line and is it possible that it is leaking. When I pump the primer, it will get hard, but if I allow the bulb to dangle or sit on the floor, it seems to lose its hardness. If I hold the bulb up to the control cables, it holds its hardness. I am going to replace the primer bulb today.

Can the primer bulb cause the lack of power problem that I describe?

Thanks,
ken

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

I installed clear hose in fuel line just before fuel filter / bowl.
I am getting bubbles big time when engine is accelerated.
I am checking for leaks in fuel line but cannot find any. I replaced fuel primer bulb and fuel line from bulb to fuel filter
I pulled fuel line off of filter just to see how it would act, It seems restricted as though the fuel lne is clogged. I checked fuel Water seperator and I had a little water in there. I tried bulb with FWS off and it acts right. It siphoned the line as it should. I am putting new FWS on and will check the bulb then.

Rain just showed up, so I will be in and out. Please keep an ear to the wall....

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

Removed all fuel lines and check valve at fuel tank. Cleared line and installed barbed fitting without check valve. No bubbles now.

Dont know if this will resolve power problem but there is nothing preventing fuel flow now.

 

[Smily]

Re: 1999 OX66 surging and lost RPM's

Put boat in water today. I still have bubbles big time at high RPM's and motor stills runs like crap.

 

[SBH2OMan]

Re: 1999 OX66 surging and lost RPM's

resurrecting an old thread here... just wondering if by now you resolved the problem...?