Power Falls Off In Turns

[mh_rogers]

I have a 1995 GSX with a fresh engine build and a coffman's performance exhaut system. Boat runs great until you try to turn it into a sharp corner then the power falls way off. Once the boat levels back up the pwer comes back on and everything is fine. While the engine was out, I put a fresh kit in the carb. Is the a jetting problem or is it a float problem or something else?

 

[robin savell lloyd]

i have a performance exhaust in my boat i have the same problem. it has unbeleveable mid and top range but it is slow to take off and in sharp turns it will allso fall on its face. I wander if the exhaust is made for top end and you lose botom end performance. this is knew to me so I allso will have to make carb adjustments and see if it will help. good luck maybe someone else will be able to give us the answers we are looking for.

 

[seadoosnipe]

Compressor hp

The compressor in your Doo is designed for power by forward momentum. It acts similar to a jet aircraft engine. The more pressure you provide to the inlet by forward momentum, the faster your gonna go. This is easily seen in the jet pumps by nosing your Doo into a dock or embankment. Give it WOT, note the amount of thruse coming from the nozzle. Then take it out on the river and do WOT, look back at the nozzle. Notice the difference in the nozzles output. You should see a big difference.
Well, the same is true in sharp turns. When you turn, the forward push into the pump is changed and now trying to come in from the side as your direction changes. This can be seen by a simple test too. Accelerate in a straigt line but maintain a speed less than wide open throttle, say 30 mph. Then, make a turn (not a super tight one though) and note the speed beginning to drop off. When that happens, increase the throttle. You'll notice that by increasing the horse power to the nozzle you can keep up with that set speed. Well, if your already at WOT when you go into that turn, you have no power left to give the engine to keep it at the speed you were at before the turn was initiated.
This is true in almost any type of boat or PWC.

 

[mh_rogers]

Thanks for the info. However, I think it might be something else that may need adjustment. For comparison I have 650 GTX and it will power out of a sharp turn with ease. Though my 580 will never perform like a 650, it still seems like something is not quiet right. The power falls off to the point of nearly killing the engine. What do you think?

 

[mh_rogers]

Hey, what kind of exhaust do you have and did you have to change the size of the jets when you swapped the exhaust? Also what size engine is in your 'doo?

 

[robin savell lloyd]

this boat is new to me and it's performance I am not sure of how it shoud be. I have no way of compairing it to a stock one yet. have you ever ran your ski before new exhaust was installed ??? have you compaired it to another stock ski???? ps. r& d exhaust it is old school i think and new larger carbs, engine is 657x

 

[seadoosnipe]

Power?

I see your point............for you to lose torque like that in a turn, when the engine is being stressed to its maximum ability, the compression would need to be tight.......

Do a compression test, let us know what you get!......

 

[robin savell lloyd]

I have 130 psi on both cylinders

 

[seadoosnipe]

140...

140 is considered new, so I'd say at 130, your engine is pretty tight still. You should get many more years of life from your bottom end before you even think about a rebuild...........:cheers:

 

[robin savell lloyd]

mh rogers. I have read that you have to make changes to carbs when ever you install a performance exhaust

 

[seadoosnipe]

Correct....

Very correct Robin. You'll need to increase the size of your main and pilot jets at least to the next size up. I tried to look up the 95 model GSX, but I can't find that model being made until 96. Any way, your main jet size is a 142.5 so you may be able to jet up to a 147.5 and get a little extra ump.

 

[robin savell lloyd]

Seadoosnipe. I sure do like to hear those words, many more years, i sure hope so

 

[seadoosnipe]

Tlc....

It's all in the TLC in how we take care of it. I was surprised at how well my 787 was taken care of by the previous owner. He had to flush it out after every outing because when I popped the heads, you could have eaten off the surface.
TLC, that makes um last............but still, that's great compression for yours...

 

[mh_rogers]

Never been run with stock exhaust. Come to think of it, I have a neighbor whose dad has a GSX. I will be talkin to him to see if I can try there boat out on the lake.

 

[mh_rogers]

This may seem like a dumb question, but we are talking about the low speed side right?

 

[seadoosnipe]

Not really...

Not really, most of the work from mid range to top end is through the main jet.