Lost RPM's

[jhosea1979]

well to start with i have a 92 pro v 150 on a 90 champion 17' 6" with a 8" jack plate last year the motor ran great 6100 rpm and around 61 mph "GPS". i have never let the boat set up for very long always on the water with if and just about a month ago it started losing rpms down to 3000 and would not even get on plane. i took the carbs apart and cleaned them and put em back on, new plugs, changed the fuel waterf seperator and got it back up to around 5000. but not matter what i do i cannot get it back to that 6000 mark. how do you go about checking the fuel pumps "Test"..... and what is the factory setting for the air mixture screw... any help would be great

 

[jhosea1979]

Lost RPM's

compresion is 118 up and down

 

[multimech]

Re: Lost RPM's

Do a leak down test on the cylinders, this will tell you definately that you don't have a problem. Compression can be built up and you can still have a major problem in the cylinder. Take a timing light and put it on each lead on each cylinder as you have someone run it near the speeds you are getting the problem at. Make sure the engine is not missing on one or more cylinders under load. Check the fuel pump pressure and check for air bubbles in the fuel line. Make sure all your throttle plates open fully....synch and link.

1000 rpm loss is a lot. The fact that you cleaned the carbs and did a few other things indicates the engine was not serviced regularly. Check everything, even your tach. You may find the tach is not working correctly.

 

[jhosea1979]

Re: Lost RPM's

Do a leak down test on the cylinders, this will tell you definately that you don't have a problem. Compression can be built up and you can still have a major problem in the cylinder. Take a timing light and put it on each lead on each cylinder as you have someone run it near the speeds you are getting the problem at. Make sure the engine is not missing on one or more cylinders under load. Check the fuel pump pressure and check for air bubbles in the fuel line. Make sure all your throttle plates open fully....synch and link.

1000 rpm loss is a lot. The fact that you cleaned the carbs and did a few other things indicates the engine was not serviced regularly. Check everything, even your tach. You may find the tach is not working correctly.

Pressure holds on the cylinder the throttle plates open fully What should the the pressure be on the fuel pumps? I have put a clear fuel filter in the line after the primer bulb and it will only stay about a 1/4 of the way full making me think fuel pumps how do you test them Also I noticed that I am having to trim the motor way higher than I have had to in the past. " could be cause of the 1000 rpm lost"

 

[CoffeeHound]

Re: Lost RPM's

Pressure holds on the cylinder the throttle plates open fully What should the the pressure be on the fuel pumps? I have put a clear fuel filter in the line after the primer bulb and it will only stay about a 1/4 of the way full making me think fuel pumps how do you test them Also I noticed that I am having to trim the motor way higher than I have had to in the past. " could be cause of the 1000 rpm lost"

Has anyone stopped to think a bit -- up trimmin -- makes me think he may have water ,, a crack in the hull !! The boat is getting older and needs attention just like a motor . Once you get the motor fixed ,,get boat weighted to see how many hundreds of gallons of water that motor is tryin to push around !!

 

[jhosea1979]

Re: Lost RPM's

Has anyone stopped to think a bit -- up trimmin -- makes me think he may have water ,, a crack in the hull !! The boat is getting older and needs attention just like a motor . Once you get the motor fixed ,,get boat weighted to see how many hundreds of gallons of water that motor is tryin to push around !!

If it was a crack in the hull you would see the water running out of it when you pulled it up on the trailer??? i have an auto builge pump that seldom comes on " only when i stop too quickly and water from the wake rushes over the transome". i just recently put a keel guard on the boat and was looking the bottom over pretty good and seen no signs of a crack, or any indication that it could be taking on water.

last time i took the boat out and it was acting up would only get to around 3000 rpms, the only thing i had done before it started acting up was change the water/fuel seperator.... i took the cowl off and remove a couple of the main jets "thinking maybe some trash/water got by when i changed the filter"' while it was running just to let some gas flow through the carbs tring to flush them out. when i put them back in and give it a try it gained rpms 3000 to 4100 or so... went home took all of the mains out, cleaned them really good flushed the carbs with the jets out, put new spark plugs put it back together and took it back to the lake "5000-5100" this trip... thus where i am now and there again the clear fuel filter i put in the line is only about 1/4 of the way full, which makes me think fuel pumps, But i have no idea on how to check them, what pressure they should pump up too ect..

 

[jhosea1979]

Re: Lost RPM's

Just for information purposes

 

[99yam40]

Re: Lost RPM's

http://forums.iboats.com/showthread.php?t=283363 look at this post for testing fuel

not sure if that motor is suppose to run 6100 RPMs
I thought most 2 strokes WOT if propped right was 5500 , but the rev limit maybe around 6K

 

[jhosea1979]

Re: Lost RPM's

Thanks for yalls help...

you are right 5500 is the max for my motor thamks for the link on the fuel system will try it this afternoon. took the boat out yesterday and got it up to 5300 rpm and about 54 mph "gps" But something still seems funny. i know when i got the boat a year ago it would run around 59-62 mph and the tach was around 6000-61 which the tach could have been wrong but my gps is

 

[jhosea1979]

Re: Lost RPM's

Ok I have done a lot of work on the boat and ruled out the fuel system altogether. But did find and fix the following carbs gaskets where coming apart letting Lil pices off into the bowl, needle valve were bad

replaced all floats needles gaskets orings ect in the carbs new fuel pumps to no avail. No help.

So I got into the electrical checked the coils cold then hot. Cold all coils ohm out good but hot #5 would not show any thing. Could that cause 800-900 rpm lost???

Also found the reg/rectifer ground wire was loose. And noticed while on the water voltage spikes on my fish finder.

Could the loose ground cause the spike in voltage? could it cause a lost in rpms?, could it be the cause of the coil going bad? What else damage could that loose ground do if any???

Also got my manual in for the motor the other day and after looking at some of the measurements in the book on the linkages I believe I might have a pro v shell with a regular 150 motor in it with the pro v carbs with the 150 jetting. Not that I think if makes a difference but just something I found Like I say last year the boat would run around 61 mph gps and now only 50. And 800-900 rpm lost

 

[99yam40]

Re: Lost RPM's

If you are loosing spark on one cylinder , that would cause RPM drop.
A timing light hooked to the different plug wires should have shown the loss of spark

 

[jhosea1979]

Re: Lost RPM's

With the cowl off water comes up to high to run it. scared of it getting into the bottom carbs

 

[jhosea1979]

Re: Lost RPM's

Trying to find where I have lost my rpms at. I have started looking into the timing after ruling out everything thing else " changing it out with new


My ? Is would a bad cdi cause a lost of rpms on top end. When I look at the timing marks while in a test tank and around 3000 rpm it only get to tdc. The book call for 28* at wot and I just don't believe it is getting the what else could cause the timing not to advance enough. Stator, pulser coil, cdi, I have not made any adj on any of the linkage science the problem showed up. Before the boat would turn up around 5800-6000 but I also noticed voltage spikes. Which I found a loose ground on the rectifer. What else could that mess up. Helpppppp please. Bout to pull my hair out working on this thing for 3 months running !!!!!!

 

[jhosea1979]

Re: Lost RPM's

ok still fighting this problem in my motor went by the book and worked the static timing but the problem is still there like the motor is not getting enough fuel or something anymore ideas on why i would have lost power 1000 rpm's and aboutt 10 mph
HISTORY:
PROBLEM STARTED: After changing water fuel seperator

Have rebuilt carbs, new fuel pumps, upgrade in octane 89 to 93, stabil always used, new fuel lines, new primer bulb
Found a loose ground on my regulator after noticing voltage spikes
Is there anything the high voltage could have messed up that caused this Also the float level in the carbs if to high or low would this cause this they look level when holding the carbs upside down

SOOOOO Confused

HELPPPPPPP

 

[jhosea1979]

Re: Lost RPM's

No help?!???