1996 challenger rpm drop once boat gets moving 787 single

[freshforest]

Hi starting to pull my hair out here hopefully somebody can help.. OK I've been over the boat cleaned the raves. Just had a local shop re-jet and set up the carbs (was told all is good in carb land) brand new, pump oil, impeller, pump bearings, wear ring. I checked the fuel selector valve which also looked great, the fuel lines are black rubber, fuel filter is clean.

Ok on take off the engine revs right to 7200 rpms the boat comes out of the hole just fine and starts to plane. (engine sounds good) once the boat comes up on plane the rpms drop to about 5300 rpm then gradually they will build to 5400 rpm then it stays there. If I let the boat lose speed once it sits back in the water suddenly the rpms will go to 7200 again the boat will plane then back to 5300 rpm and over and over and over. If I leave it w.o.t it runs fine just 5400 rpm.

It did this before I had the carbs looked at

Im stumped and I just want out on the river, any ideas would be great!!

 

[DonoBBD]

Just had this with ours this week. If when she takes a set on plain and when it would lay over let off the power about half way or more then pin it wot again. It will clean out and go. Seems to be with the governor.

This is on a new motor and rebuilt carbs. There must be some type of adjustment.

Dono.

 

[freshforest]

made some progress

Today I took the water flow regulator apart and inspected the needle and seat ( If one can call it that ) The shaft was bent (which I straightened ) and the needle part was worn in a uneven pattern. I also checked voltage at 5500 rpm at the battery and it was 13.6 v. Anyway I put it all together again took it out and it ran the same except the rpm dropped to 5500 then gained back to 6000 at this point if I held W.O.T it would stutter a little and slow down to 5500 rpm. With some carefull throttle manipulation I could get it back to 6000 but I can't hold the throttle wide open it will only do 6000 rpm at 3/4 throttle. This is better than before, so I ordered a new flow regulator valve, hopefully that will fix the issue..

Fingers crossed in Kamloops

Hi starting to pull my hair out here hopefully somebody can help.. OK I've been over the boat cleaned the raves. Just had a local shop re-jet and set up the carbs (was told all is good in carb land) brand new, pump oil, impeller, pump bearings, wear ring. I checked the fuel selector valve which also looked great, the fuel lines are black rubber, fuel filter is clean.

Ok on take off the engine revs right to 7200 rpms the boat comes out of the hole just fine and starts to plane. (engine sounds good) once the boat comes up on plane the rpms drop to about 5300 rpm then gradually they will build to 5400 rpm then it stays there. If I let the boat lose speed once it sits back in the water suddenly the rpms will go to 7200 again the boat will plane then back to 5300 rpm and over and over and over. If I leave it w.o.t it runs fine just 5400 rpm.

It did this before I had the carbs looked at

Im stumped and I just want out on the river, any ideas would be great!!

 

[seadooya]

raves cleaned? If so, then i'd rebuild the W.R.

 

[freshforest]

cleaned the Raves

raves cleaned? If so, then i'd rebuild the W.R.

I cleaned the Raves but only the valve part not the slots in the engine. Both valves were pretty clean already and slid easily in and out of the slots..

 

[seadooya]

clean the slots, and the "hole" at each valve housing.

 

[freshforest]

out of the hole..

clean the slots, and the "hole" at each valve housing.

I'll do it, but I was told if the engine still does 7200 out of the hole then the Raves were not needing attention..

 

[seadooya]

its doin 7200, cuz theres "no load" on the pump. Probably though, you'll nee to rebuild/replace the W.R.

 

[DonoBBD]

Could some one explain to me this part and what its purpose is?

This is better than before, so I ordered a new flow regulator valve, hopefully that will fix the issue..

I am guessing this is the part refer d to later in this thread as the W.R.?

Don.

 

[freshforest]

waterflow regulator

this is the thing that looks like a third rave valve on the exhaust .. It has two water lines hooked to it one from the intake hose and one goes to the tuned pipe for cooling. As water pressure increases it forces the valve closed which reduces flow to the tuned pipe. How this affects power and rpm is beyond me but that is what it is

Could some one explain to me this part and what its purpose is?

This is better than before, so I ordered a new flow regulator valve, hopefully that will fix the issue..

I am guessing this is the part refer d to later in this thread as the W.R.?

Don.

 

[DonoBBD]

this is the thing that looks like a third rave valve on the exhaust .. It has two water lines hooked to it one from the intake hose and one goes to the tuned pipe for cooling. As water pressure increases it forces the valve closed which reduces flow to the tuned pipe. How this affects power and rpm is beyond me but that is what it is

Thanks for the info. I know two strokes quite well but this water squinter is different.

Any info on a do it your self rebuild for this valve gate?

Cheers Don.

 

[freshforest]

valve gate

I had a job today but I will look into it tomorrow, that WR should be easy to rebuild I think

Thanks for the info. I know two strokes quite well but this water squinter is different.

Any info on a do it your self rebuild for this valve gate?

Cheers Don.

 

[DonoBBD]

I had a job today but I will look into it tomorrow, that WR should be easy to rebuild I think

I wonder if my problem could be freshforest's problem. When I pulled my pump the one line that gos to this WR gos into the pump into the vacum area of the jet. I took this line off to pull the pump on the hull side then pulled the pump. That black pipe didn't come with the pump. It had been broke off at the end of the threads. Some one thought that if they goobed it up with black RTV it would seal it. I am guessing this is a high pressure or vacuum line. It was broke because it was red lock tighted in. Hoping a plumbing part will work from a hardware store. IF not I will have to order one.

Any how I will be fixing this before my pump gos back in after I fix the drive line. I bet this will fix my variable tune of the exe pipe and my bog.

Cheers Don.

 

[freshforest]

water supply line

I had the same problem with my water supply line and I used plumbers goo and it worked great ( no leaks so far) you know shoe goo??? Well theres plumbers goo too! lol If your pulling the pump make sure you silicone it back in to get a good seal. I also read that all these boats have leaks between the ride plate/ pump shoe right from the factory.. they recommended all boats have the ride plate / pump shoe removed, cleaned and re sealed.

I wonder if my problem could be freshforest's problem. When I pulled my pump the one line that gos to this WR gos into the pump into the vacum area of the jet. I took this line off to pull the pump on the hull side then pulled the pump. That black pipe didn't come with the pump. It had been broke off at the end of the threads. Some one thought that if they goobed it up with black RTV it would seal it. I am guessing this is a high pressure or vacuum line. It was broke because it was red lock tighted in. Hoping a plumbing part will work from a hardware store. IF not I will have to order one.

Any how I will be fixing this before my pump gos back in after I fix the drive line. I bet this will fix my variable tune of the exe pipe and my bog.

Cheers Don.

 

[DonoBBD]

I had the same problem with my water supply line and I used plumbers goo and it worked great ( no leaks so far) you know shoe goo??? Well theres plumbers goo too! lol If your pulling the pump make sure you silicone it back in to get a good seal. I also read that all these boats have leaks between the ride plate/ pump shoe right from the factory.. they recommended all boats have the ride plate / pump shoe removed, cleaned and re sealed.

Great tip. I will do just that.