5k and 38 mph tops. help please

[spankzilla]

Challenger 2000 240 efi will not turn over 5k and will only run 38 with two adults and half tank of fuel. First I know I need to do the job weld fix on my wear ring. Prop looks good. I'm assuming wear ring is playing into top speed but I'm confused cause I thought if it was cavatating the rpms would sky rocket? It runs great right up to 5k no missing sputters or anything just won't turn any more. I verified throttle is open all the way.
List of new parts
Power head just out of break in
Tps sensor and set correct
Both temp sensors
New plugs
New filters
Fresh gas
Fuel pressure and comp good
No throttle guardian that I can find I assume it was already removed.



Any ideas what would limit the motor or do you think its just the prop wear ring? Thanks for any help.

 

[spankzilla]

And when its at 5k its running really smooth and will bump 5500 if I turn it hard.

 

[spankzilla]

Pulled the new plugs back out and one of them still looks new so looks like dead cylinder is my rpm problem. Now just got to find out why when I get a chance .

 

[Dr Honda]

Yep....

I was just going to say.... Smooth running, and low top RPM... you have a dead cyl.

Check...

1) compression
2) coil(s), wires on the dead cyl(s)
3) injector(s) on the dead cyl(s)


If the compression is OK... then I would verify that you have a good ground on the ignition coil, for the dead cyl.

 

[spankzilla]

Comp is spot on with other cylinders. After a quick check before work it is firing but that is after I checked plug wire, coil connection, and ground so it may not have been firing before I did that. My fault for not checking it first, but it got me to wondering if it was firing the whole time but had an injector not working wouldn't it have burnt that cylinder up? It was ran for about 1-1/2 hours like this. Thanks

 

[Dr Honda]

Yes... it would be bad if no fuel was flowing in, since the oil is mixed with the fuel, in the vapor tank. But... if there wasn't any fire... there's no (minimal) heat. So... you wouldn't get a "melt-down" but you would wear the rings, and piston very badly.

Did you check for spark on the cyl that was dead?

 

[spankzilla]

Yes it is firing the plug now but not sure if it was during the run time. the compression is good and several times like 8 or so i stopped and shot all 6 cylinders with a temp gun and they were all between 110-117 so im hoping it was getting fuel and i didnt mess a brand new motor up. Surely if it wasnt getting fuel i would have seen a temp difference. But today i worked on it a min before work. I pulled #6 plug left it in the plug wire boot shorted it to the head and it was giving a big blue spark so i reinstalled the plug. Cranked the boat on the hose and it didnt seem to be idling any different so i pulled #6 plug wire off and it made no rpm change so the cylinder is still dead. Either its not firing when assembled or its not getting fuel but i would think compression would be low and would have seen the heat difference if that was the case. Im going to go ahead and do the injector testing next though to be sure.

 

[RiverPro]

Good advice so far, most often the dead cylinder runs cooler. Since your temps are equal, I'd scope #6 or pull the head for a looksie.

As too your rpm and wear ring ring question, a questionable imp-ring will allow for higher rpms. Another thing, back her in the water and leave her on trlr while testing/sorting this out. Most often, you'll hear "bad stuff" as it begins to happens. (Beats being stranded on the water)

Side note: Consider double checking #6 cyl reeds.

 

[spankzilla]

Injector #6 def not working. It wasn't spraying anything out during spray test and just looks bad compared to the others.

 

[spankzilla]

 

[spankzilla]

Guess I'll pull the head 2 Moro and see what I can find. I borrowed a dealt inspection camera but it won't go into plug hole.

 

[Dr Honda]

Yep... looks like the bottom of the engine was under water at one time. That's why the injector is rustier than the others. I'm sure you can find on one ebay

 

[spankzilla]

Yeah i found several prob order one 2nite. Im just worried about how the rings and cylinder look.

 

[spankzilla]

Oh and once again thanks for all the help DR!

 

[spankzilla]

Guess I was very lucky. Pulled the head today and cylinder still looks new. Waiting on injector now.

 

[spankzilla]

Dr honda, Got the injector in and went for a run. Boat will now do 5,500 and 40mph real quick and will gradually increase to 57 maybe 5, 800 and almost 45mph. Any ideas what I should check next now that i know all cylinders are hitting? Thanks

 

[Dr Honda]

Did you check the temp on all 6 spark plugs? Sounds like it's still not running on all of them.

 

[spankzilla]

Yes i did and they were all close, But they were with the bad injector also. The new plugs make it appear all cylinders are good now(color etc). But it does seem to kinda be the same thing as one cylinder down. It will run right up to 5,500 no missing or cutting out its just like its done and their is no more. Unless one of the cylinders is firing at low rpms and maybe not hot enough for higher rpms? I guess I should do a spark gap check on all six.

 

[spankzilla]

Another thing is when i fixed the bad injector it definatly changed the idle. I had to idle it down about 400 rpm's and it seemed to smooth the idle up a little, but that brings me to my next question how smooth does one of these motors idle? I have never been around another one and this one didnt run when i bought it so im not sure if the idle is right or not. It has a very rough cut up idle like a chevy with a large roller cam, maybe normal maynot be i have nothing to compare it to.

 

[Dr Honda]

It's smooth for a 2-stroke engine... but it's still a 2-stroke. (think old dirt bike, or chain saw)

The idle should be around 900 in the water. Don't try to make an adjustment while on the trailer.


I would put the boat in the water... run it +70% on the throttle for a minute or two... and shut the engine off WITH OUT pulling it back to idle. Then... check the plug temps, and pull them to check the color.

While 5500 rpm is at the bottom of the acceptable levels... it's not normal Most guys will see 5800 to 6200 RPM.


While under the deck lid...

1) Make sure the throttle is physically opening all the way.

2) Make sure the tach is reading right. (could be off)

3) Check the compression. If you are 15~20 psi low... then the engine is getting tired and that may be all she has. I know you said they were all close to each other... but you never posted the actual pressure. 135 is great... 125 is fine... lower than that, and you will start to loose power.

 

[spankzilla]

I will check the plugs again. As far as compression goes ill have to check it again but i bought this powerhead brand new and it only has about 8-9 hours runtime so i hope its good. I did check all 6 when i first installed it before ever running it and they were between 123 and 127 i just figured the numbers were low because the rings hadnt seated yet so i will check again.

 

[RiverPro]

Model YR 240s usually run ~ 6K RPM / Idle sounds bad azz, however the PH should "look" relatively stable / Ethanol can wreak havoc on old fuel lines, look for signs of internal hose failure. I see you checked fuel pressure, I'd suggest checking fuel flow. Guessing of course, however great up to 5500 then levels off is a sign of low fuel flow.