ls2000 engine not running at full capacity

[Robert Frost]

I have a 2001 LS2000 jet boat with twin 1200 2 stroke engines. One engine runes fine out of the water but when in the water, it only goes to about 4000 RPMs and than will shut down. I replaced the spark plugs, CDI and the stater but I still have the same problem, The compression is all three cylinders is at 115 to 120 psi. I have changed the fuel filter. The other engine works fine. Does anyone know what I might do? Thanks. Robert in Arizona

 

[DCB-270]

Sounds like a compression issue but you said that was good.

 

[DCB-270]

Maybe the reeds?

 

[DCB-270]

Or carbs.

 

[Beachbummer]

I vote for fuel starve too.

 

[4x15mph]

It sounds like a cooling system problem potentially. If the coolant sensor triggers, it will limit the rpm's to ~3500 RPM's. The exhaust chamber is known for getting clogged and may need to be cleaned out. There are 3 holes that can clog up with sediment. You can feel the exhaust (blue) and compare to the working engine or use an IR thermometer (harbor freight = cheap) and compare the temp between engines.

See my post here when I had a similar problem: https://jetboaters.net/threads/cleaning-out-the-cooling-system.3671/page-2

Otherwise, it can be a host of things like carbs/fuel since running under load (in the water) is very different than running out of the water.

 

[Beachbummer]

Pull the choke as is about to die. If rpms go up for an instant before shut down it is likely fuel.

When was the last time you cleaned the carbs?

 

[Mainah]

I have rebuilt 4 rotax 2 stroke engines 8 mikuni carbs. After rebuild on one engine I just could not get proper power and throttle response out of and determined it to be the carbs. No matter what I did I could not get the carbs to deliver the proper fuel and air mix even when I did I get the pop off perfect on my bench with the same jets as on my other carbs. I bought brand new carbs for that engine and the problem was solved.

@4x15mph has a solid recommendation as well.

One more thing to check it that the gear oil pump is working and the oil lines are not clogged. You will quickly end up with a FUBAR engine if not getting oil.

 

[Beachbummer]

I also would buy new carbs from mikuni vs rebuilding. My 720 had single carb at $200 so it was an easy call instead of rebuilding. I added a spin on fuel filter water separator and never had to deal with this problem since installed. I did sell the boat, but I was impressed at how the filter preserved the carb.

 

[Robert Frost]

Thanks for all the suggestions. I did rebuild the carbs back a year or so ago but maybe I missed something. The engine has 3 carbs. I may check the cooling system first.

 

[swatski]

So, when is the last time you ran the boat before these new issues? If its like a year or two or more - your carbs are all gelled up, no question about it.

EDIT: Sorry - I see you already addressed that!

--

 

[Robert Frost]

Maybe it is a cooling issue. I will look into that. But I have been back to the lake 3 or 4 times to test the boat and I do not even have to take the boat off the trailer to test the engine. I just back the boat into the water to test the engine. Is just does not do well in the water even before it has had time to warm up unless it gets warm right away and the sensor is what is keeping it from going over 4000 RPMS. But would the sensor not register if I were testing the engine dry without water for 10 seconds or so? Or when I hook the hose to the engine and run the engine at home with water running through the cooling system, shouldn't the sensor do the same thing off the lake? Thanks for all the help. Robert in Arizona

 

[4x15mph]

Agree based on your info that it may not be cooling. You can pull out the sensor and Test it in boiling water or you could switch sensors between the 2 engines.

When i had an issue with RPMs on 1 engine, I swapped the carb racks between the 2 engines which wasn’t hard. Just required new gaskets and as it turned out, it wasn't the carbs. It was cooling

 

[Yamatuf]

Sounds like you have a pecking list, great input group.
1. Sensor
2. blockage
3. plug wires / you may have a broken/ fatigues wire. if original I would definitely replace all six
4. Carbs ? just rebuilt, are settings correct?
5. Maybe swap your ebox to make sure it's not electrical/bad cdi or wire even though you replaced?

Jet ski solutions can make new wires and rebuilt carbs. - he did a great job on mine.

 

[Robert Frost]

Thanks again for your suggestions. I did swap the CDI from the good engine with the one from the bad engine but it did not make any difference. I have spark to all six spark plugs so I did not think it would be the wires. But if you suggest it, I may go ahead and swap out or buy new ones. Is there another way to test? I can check the carbs again. I am just getting tired of all work and no play with this boat since it has not been working well for the last few month.

 

[Yamatuf]

Download the ls manual, it explains how to check the ohms for the plug wires and sensor. If they are original it may be the root of the problem. You could switch / swap the complete ebox out or just swap out the coil packs. You will have to open both eboxes to just switch coils. My old original wires were faulting out, decaying and causing similar issues. They wires will fail as more power is requested. I believe there is a way to override the heat sensor for testing purposes.

Jetskisolutions can fix them in a jiffy, plus you get to pick a color.

 

[Robert Frost]

Thanks again. As you may see, I am new to this site. Where might I go to down load the manual?

 

[4x15mph]

Robert - PM me with your email address

 

[Juan Mejia]

Hi folks, I'm having the same issue. I need all the help I can.

 

[Juan Mejia]

It sounds like a cooling system problem potentially. If the coolant sensor triggers, it will limit the rpm's to ~3500 RPM's. The exhaust chamber is known for getting clogged and may need to be cleaned out. There are 3 holes that can clog up with sediment. You can feel the exhaust (blue) and compare to the working engine or use an IR thermometer (harbor freight = cheap) and compare the temp between engines.

See my post here when I had a similar problem: https://jetboaters.net/threads/cleaning-out-the-cooling-system.3671/page-2

Otherwise, it can be a host of things like carbs/fuel since running under load (in the water) is very different than running out of the water.

Hi. Where are these 3 holes?