657x fuel line restrictors?

[98sportster1800help]

Okay so let me start with some background. I've done much research but nothing seems specific to a certain ski with that said this motor is from a '94 XP (657x). The motor has been completely rebuilt and taken from that ski and put into different ski. Ski runs great until it's in the water and won't plane out or get over what feels like 4500 RPMs though it reaches 7000 on a stand. I plan to replace the regulator today however I remember back in the day some skis had restrictors in their return lines and because this had the gray temple lines I decided to change the lines and totally forgot, threw away the old lines and now I can't look back to tell. From what I read some people say there's a restrictor between the carb and the fuel tank in the return line others say that there is a restrictor between the accelerator pump and the carb. Not sure the truth looking for somebody that has knowledge on this thanks.

 

[etemplet]

I'd look at the impeller that's on the ski first thing and make sure it is the correct one. You may not even have an engine issue. What is the different ski? Carbs are not set the same for each hull. Make sure you have the correct numbers for the year ski you are installing the carbs .

Low pop off , even in range, can cause the ski to stumble and not get over the hump. Sometimes jumping a wake will unload the impeller and the ski will take off and rev properly till you slow back down and then... same problem. I fought this for a while with 2 787 GTXs. Also I would check and make sure the the ports inside the carb barrel are flowing very well when yo udo the test. (see mikidymac's carb thread)

Good Luck !

 

[98sportster1800help]

Oddly enough it's been modded and fit inside a supercharged yamaha hull. That said the pump will be larger and I know that will deflect from torque once topped out should catch up but pump is clean and good. I just fitted a tach temporarily to it to test. After I get the new regulator in it it will go back on the water to determine what peak rpm it's hitting. Would like to rule out as many options as possible as time to drive to the lake is limited. Also compression is 135/138. Per ear drum tach, I'm estimating 4500 rpms

 

[etemplet]

In that case I'd really look at the impeller pitch. there is a good chance your asking to much of the engine. It's only 85hp. Next time you go out... jump a wake and see if the impeller unloads and the ski revs. 4500 is a big Seadoo Transition point. You're kinda in no man's land with this set up. Regular Seadoos give us enough trouble. LOL Good Luck !

 

[98sportster1800help]

Unfortunately there's no jumping anything at 23 mph

 

[etemplet]

I'd start with less pitch on the impeller. What is the weight difference on the hulls. I had a 657X on a SPX and an older GTX. Fairly light skis especially the SPX.

 

[98sportster1800help]

I'm not sure the pitch but it is a stock Yamaha jet pump and impeller well the hull is probably heavier it's quite a bit longer so it should help it not having to worry about porpoise or the nose pointed straight up. Most of the wait and those big skis are all the drivetrain which is no longer in it. Even so you would assume whether it be getting "traction" or not it would still top out or rev up to where it's supposed to go and it is not unfortunately

 

[etemplet]

After reading and perhaps understanding what you are doing I'd say you're gonna have to make some changes in design. A small pitch change on any ski can easily bog the engine... which is why changing to a more aggressive pitch prop doesn't make the skis faster. It can also slow them down. Engine doesn't have the power to turn it. Good luck with your new design. LOL

 

[98sportster1800help]

Again just trying to rule out obvious things (as many as possible) before I bring it back. Ive done a similar swap before with a kawasaki 750(much easier as well) but here is the info in manual about orifices.

 

[98sportster1800help]

I'd start with less pitch on the impeller. What is the weight difference on the hulls. I had a 657X on a SPX and an older GTX. Fairly light skis especially the SPX.

I 100% agree with you on this. It revs out of water to 6700+ on the tach and sounds good and only gets to 3900 in water. I tried to keep it on the trailer and put it in the water just enough to keep the exhaust out but the impeller to suck water and it still was weak. I wanted to rule out the fact that maybe the exhaust was restricted. Also even at Idle the thing is going Pretty good I can tell it has a steep pitch. Wonder how I can take some pitch out of it?