2001 90hp 2-stroke missing and hesitating

[captmello]

I've got a 2001 90hp 2-stroke, loop charged, vro motor that I've been running for three years now. When I bought it, the carbs were leaking badly, so I pulled them, rebuilt them and replaced the floatbowls which were warped. After this it has run great ever since.

Now, this week, it has started to run badly. Sometimes it will idle fine, sometimes it won't idle at all, not even at 1200 rpm, just dies. under power it can be cruising along at 1500 rpm and the motor just dies...It will always restart. If I give it no throttle it will fire but die right away. If I raise the throttle it will start and run as long as I keep the throttle up over 1500-2000 rpm. I can drop the throttle and shift into gear quickly enough to get going, but it can be a challenge. Now, once its cruising above 2000 rpm it misses, and hesitates, but runs up to almost normal WOT rpms, but still is missing, etc.

The fuel is two weeks old and I replaced the fuel/water filter but that was no help. There was no water in the old filter which was just a year old. I checked the filter mounted in the the engine fuel intake and it appeared clean.

I pulled the plugs and they all looked fine.

I'm not sure of my next move. I really think its seems fuel related but fuel flow seems good.

 

[Bosunsmate]

Re: 2001 90hp 2-stroke missing and hesitating

You could run it at night and look for shorts.
Have you recleaned the carbs?

 

[captmello]

Re: 2001 90hp 2-stroke missing and hesitating

You could run it at night and look for shorts.
Have you recleaned the carbs?

Thanks for the reply. No I haven't recleaned the carbs. I guess i didn't think they would need it. But I will add that to my list.

Is it normal to need to clean the carbs every few years?

 

[captmello]

Re: 2001 90hp 2-stroke missing and hesitating

Well, I haven't gotten any further with this issue. I installed a new fuel supply hose and tried running the engine on a different tank to make sure my fuel supply was not the problem. It ran the same so I reconnected the onboard fuel supply.

So here's what I know.

1. The fuel and fuel supply is not the issue. Gas is new and flowing fine. New fuel/water filter is installed and the filter at the motor is clean.

2. The spark plugs are in good shape.

3. The engine will Idle fine at times, but usually will not idle under 1500 rpm. Over 2000rpm the boat will not stall, but continues to miss and hesitate all the way up to WOT.

4. I noticed that the primer ball does not seem to firm up. It seems to pump but doesn't get hard. Is this a sign of something? I tried pumping the primer ball while running the motor but doesn't effect the running problem anyway...

Without a complete understanding of the fuel system, I'm having trouble figuring out what this could be. I do not believe the carbs are clogged up. The boat ran fine one day, then it began to stall at idle. It seemed to get progressively worse after a day or two running this way.

Trying to get a handle on how the fuel system works... Could I be getting air leaking into the fuel system at the motor somehow? Or is there a central control of the idle circut that could be causing the whole idle circut to fail???? And if so, would this also affect the running at higher RPMs as well???

If anyone can give me some help, I sure would appreciate it.

 

[captmello]

Re: 2001 90hp 2-stroke missing and hesitating

I'm still searching for my problem. On further inspection, my primer ball does harden up.

I'm wondering if I can pressure or vacuum test the engine side of the fuel system for air leaks and how to do it.. I've read that could be a problem...
I'd like to do any testing I can before pulling the carbs.

Any input is greatly appreciated.