Engine problem: won't exceed 4000 rpms. Need help please!

[Blue in Yarmouth]

O.K., so I joined this site a year ago after purchasing a boat from a man who I have since decided knowingly ripped me off (then moved away). I have had the boat for over a year and have still yet to get it running properly. So far I have : Changed a starter, had one engine rebuilt, hard carbs on same engine rebuilt, and basically just told the mechanic to find what the hell is wrong with the boat and fix it.

I got the boat back from the most recent attempt to rectify the problems and this is what I have now:

One engine (that if the guy I bought it from can be believed... was rebuilt just prior to me purchasing it) seems to be running fine. It gets up to 7000 rpms with no problems at all. The other engine (that I just had rebuilt and the carbs as well) will not exceed 4000 rpms and is pretty sluggish getting there. Also there doesn't seem to be any top end on the throttle, as I basically hit 4000 rpms at 3/4 throttle and the last quarter gets nothing.

Having found these things out we have done the following things to try and find the problems:

Checked compression on the effected motor (150 in each cylinder)
Checked spark in each plug (good spark in one, poor in the other)
Trimmed back spark plug cable on effected plug (resulting in good spark at plug)
Check electrical connections for corrosion (everything in the box looks like new, honestly must have been recently redone because it literally looks like a brand new setup).
These things have produced no results in terms of fixing the problem with the rpms

I spoke to a mechanic on the phone yesterday who said to do the following:

Check the rave valves and make sure that they open and close freely and check the bellows (I'm not sure what I am checking for with the bellows, he wasn't clear)
I forget the name of the other thing he told me to check (potentially the pressure regulator) but it has a cap just like the rave valve and is on the exhaust. He said to check for the same thing (that it is opening and closing freely and the bellows).

I checked those things and since I have no experience with this stuff, I pulled the caps off the ones on the working engine to try to compare. There was a definite difference in the way the rave valves on the effected engine felt in comparison to the ones on the working engine. It almost felt like the ones on the effected engine felt gritty when I was lifting them and letting them go, definitely not smooth like the other ones. I also noted that the red center of the cover was about 1/8" deeper on the effected engine than the working engine. Not sure if that would be considered normal, but I thought I'd mention it.

For the other thing (pressure regulator I think) I did the same thing and compared it with the other side. Again it seemed to move much smoother on the working side than the effected side. It also seemed that there was a lot more play in the effected side (it was not as tight feeling as the in the working side) and I could pull it up a good 1/4" further than the one on the engine that was working. The screw adjustment on the two were pretty similar, but the one on the working side was a pretty much flush with the top while the one on the effected side was a few turns in. Again, I didn't know exactly how to get the assembly out so I couldn't inspect the bellows, but that is what I was able to see.

This is a bit of a side note. When removing one of the rave valve covers from the working engine I found some oil on one of them. Not a lot, but definitely some oil there. Is that a really bad thing or does it not mean anything?

Basically I'm stuck. I want to get this thing in the water so my wife can stop telling me what an idiot I am for buying this (even though I know she's right at this point). Does it sound like I am on the right track or am I wasting my time checking these things? Also, if anyone can tell me how to get at the bellows in the rave valve and the regulator I would appreciate it.

Finally, now that I see that the rave valves on the effected side are not working like on the working side, what the heck do I do to try to fix it? Sorry, I must sound like an idiot, but I'm trying to learn on the fly here and things aren't coming too easy.

Thanks to anyone who takes the time to respond.

 

[Britrick]

If this guy has just rebuilt this engines and carbs then your rave valves should sparkling and shiney and not be any problems with them . The bellows are the rubber diaphragm that you see when you remove the black plastic cap by pushing across the metal spring clip. There should be no holes in the bellows and they should be secured around thier circumference to the metal body .

 

[dbracela]

Follow this link to service the rave valves:

http://www.seadooforum.com/showthre...vice-Rave-Valve-Pictorial&p=349961#post349961

Set them to spec, which is probably where they are set on the working engine. If they won't open there's a chance that may be causing your issue. Pay attention to the o-ring on the stem. If its hard or cracked or generally crappy, replace it. Hell, replace it anyway.

The rave looking thing at the back, on the resonator, part # 16 to 29 here:

http://fiche.seadoowarehouse.com/se...ake=seadoojb&a=180&b=16&c=0&d=-COOLING-SYSTEM

is the pressure regulator (water control valve) for the cooling system. They aren't supposed to be adjusted as they are set to spec at the factory. However, if the PO screwed the cap in, or out, you'll have to find out what the correct setting is and set it. In order to inspect it properly, you'll have to take it off. Take it out, Take the cap off, don't lose the spring under there. Hold the plastic nut tight while unscrewing the pin from underneath/inside with a flat head screw driver, the pin will come out, don't damage it. This will allow you to lift the bellows up slightly so you can access the metal clip holding the bellow onto the housing, is a small clip, not the ring holding the top of the bellow in place. Chances are that clip is rusted out. You can replace it with a small, good quality zip tie (there's a thread on it here somewhere). Inspect the bellows as you would on the raves. Replace as necessary. Put it back together and set it.

Not a lot of people say the regulator will affect rpm's, but, it's listed as a possible cause in the troubleshooting section of the shop manual. Which I highly suggest you download.

I honestly hope this fixes your problem, I know it's not much fun chasing gremlins while your wife gives you "the eye." I'm in the same boat sorta.

As a side note, you posted this in the pwc forum, you'll get better luck posting in the 2 stroke boat section. Good luck man.

 

[Dr Honda]

The RAVE's won't keep it from reving up. They just move where the peak power is.


There has been a few thread lately where the MPEM went bad, and kept the engine from reving up.


But... with that said... does it feel like an electrical issue? (like the ignition is cutting out)

I'll move this to the boat section.

 

[Blue in Yarmouth]

@ dbracela

Thanks very much for your help. I will get on that as soon as I get a chance.

 

[dbracela]

Dr.Honda makes a good point about the raves though...

 

[Blue in Yarmouth]

@ Dr. Honda

Thanks for your reply and for moving the thread (I didn't realize I put it in the PWC section).

As for your post I was told by the mechanic if the valves are "sticking" they can cause a dramatic decrease in peak rpms which is why I have been trying to check them. Also, in looking at the shop manual it says the same thing in the trouble shooting section.

Edit* I just checked the manual again and it said "for challenger 1800 only, rave valves not closing" in the trouble shooting section can cause the engine to not reach full rpms.

As to whether it could be an electrical issue, beats me, I don't know enough to tell. What I can say is it seems to run a little rougher than the other one, but other than that it just runs at low RPMs. It won't stall or cut out or anything like that.

I had a guy tell me he thought it could be the rev limiter, but that doesn't make sense to me as I figured that would effect both engines, not just one...or am I wrong in thinking that,. I would think the same with the MPEM...being that the boat only has one, wouldn't a problem with that affect both engines? That's a genuine question, I'm not trying to say it as fact.

 

[Blue in Yarmouth]

If this guy has just rebuilt this engines and carbs then your rave valves should sparkling and shiney and not be any problems with them . The bellows are the rubber diaphragm that you see when you remove the black plastic cap by pushing across the metal spring clip. There should be no holes in the bellows and they should be secured around thier circumference to the metal body .

The rave valves were not sent with the rebuild. The company that rebuilt my engine specifically said to remove them before shipping the engine. The previous owner I have no idea about what he did.

 

[Murph_13]

I previously had a single engine Challenger (787 motor...same as yours) that developed a leak in the water regulator (leaked at the fitting to the plastic housing) and I had the exact same issue you're having...the motor would not pass 4000RPM...fixed the leak and fixed the problem. So from first-hand experience a leaking water regulator can cause your condition.

You may see evidence of the leak on the water box/muffler dependant upon how long or how much it's leaking. You may want to look for a leak with it running in the water if you don't find anything obvious when inspecting it out of the water.

 

[dbracela]

You may want to check this, but I just read that the correct adjustment is three turns out from tight for the regulator.

 

[IDoSeaDoo]

Not sure if the wires are long enough, but you can eliminate the electrical possibility by simply crossing the wires and hooking up the bad motor with the good plugs/MAG connector. Worth a try...

 

[Blue in Yarmouth]

Not sure if the wires are long enough, but you can eliminate the electrical possibility by simply crossing the wires and hooking up the bad motor with the good plugs/MAG connector. Worth a try...

I did think of that, but I think the cables are too short for that to work. I'll double check and see.

 

[Blue in Yarmouth]

So...I have tried a number of things and nothing has seemed to work. I cleaned the rave valves and in doing so found that the ones in the affected engine didn't have the grooves so I replaced those hoping it was the problem. Turns out I was wrong. Starboard engine still won't rev past 4500 rpms (the cleaning helped a bit, but not much as you can see) and now the port engine will hit 7000 rpms but at tiimes it hesitates a bit. If i drop the throttle and jam it wide open while this is going on, it opens right up, but as I say...occasionally it is hesitant.

Seriously, this boat is going to give me a heart attack as I can't seem to get it running properly and there are no mechanics around here that work on them. My wife is giving me shit about it all the time and I just want a boat that runs right. Anyone that could give me any ideas on what might be causing the problems I stated above would be a life saver at this point. Help Please!

 

[dbracela]

Were you able to cross the wires like idoseadoo suggested?

 

[Blue in Yarmouth]

@ dbracela No i am not able to do that as my cables aren't long enough.

I am going to try and explain what I did without know the actual terms of the parts I disassembled so bare with me here.

I took off the rear of propulsion system so I could get a look at the impeller, wear rings etc on the affected engine just to make sure everything was alright. In doing so I also decided to look at the other side as well. Everything looked fine initially but I decided to pull the impellers to have a closer look. When I took off the cone on the affected engine it was completely filled with water, not one bit of oil at all. The other side was fine and both impellers/wear rings looked in good shape.

When putting everything back together it seemed that the impeller on the engine that was working well went on easy and turned pretty easy as well. When I put on the other one it was pretty difficult to turn that impeller. Prior to putting the cone back on I could easily turn the other one with my fiingers but this one was hard, like I had to exert a decent amount of force and when it would turn it wasn't turing smoothly at all like the other one. It would turn hard and then kind of release and go freely for about a full turn and then kind of...i don't know how to explain it...fetch up and be hard to turn again.

What I am wondering if any of this could be leading to the rpm issues I'm having on this engine because nothing I have tried so far has worked. Any help would be greatly appreciated and again, sorry for the lack of technical terms. I hope I conveyed myself well enough for people to understand what I was saying.

 

[IDoSeaDoo]

Try running the affected engine out of water with the pump off. See if it spools up like the other one. I would think this is at least PART of your problem. The impellers should turn smoothly and effortlessly. You might be able to get away with just a rebuild kit for it.

 

[Blue in Yarmouth]

Try running the affected engine out of water with the pump off. See if it spools up like the other one. I would think this is at least PART of your problem. The impellers should turn smoothly and effortlessly. You might be able to get away with just a rebuild kit for it.

I hate showing my ignorance but what is "the pump"? Sorry, I am really new to this stuff as you can see.

 

[IDoSeaDoo]

I hate showing my ignorance but what is "the pump"? Sorry, I am really new to this stuff as you can see.

Oh man, don't feel bad, there's a lot of seadoo lingo out there. We were all there at some point or another The impeller and its housing is commonly referred to as the pump. Not 100% if that includes the nozzle, but you get the idea.

 

[Murph_13]

The pump that had water where there should have been oil is going to need to be disassembled and inspected...most likely rebuilt.

You could swap pumps if you wanted to rule out that as your problem with the low RPMs.

Did you rule out the water regulator on the water box/muffler as being the cause of your RPM loss?

 

[Sportster-2001-951C-Stock]

I'm not liking the tight pump, it should spin freely. Was the housing getting hot?

You're going to need an impeller tool eventually anyway, and it's starting to look like you might need the tools to press those pump bearing cages in and out so you can replace them, assuming you don't have something for that already. Might be a good idea to bite the bullet and get the pump issue out of the way with new bearings and possibly a new shaft if it's got grooves in it or it's bent even.

Maybe I misread something, you can't say this pump issue isn't the root cause of low engine speed, right?

 

[Albysure]

I crushed the small bearings before on my pump housing... Its flat.... mine was so tight the first time i did it that my enhine would not turn over...i just had to bearly loosen it....Try to Unloosen it a little... But they might be shot at this point from over heating