Yamasaki 701SX

I’m building a 1991 550 sx with a stock 2017 62t 701 that I am swapping in. The exhaust hose diameter appears to be much larger on the 701 than 550. Does anyone know what has been done when interfacing with the rear exhaust system on sx boats with this swap? Remove the exhaust tube and punch a hole for a bigger exhaust? Potentially downsize the hose..? Seems restrictive. Thoughts?
 
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If you’re gonna keep it longer than a year, put the larger diameter exhaust tube in. While you’re at it, widen the tray. It’s very restrictive.
 
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Sanoman

screwthepast,makeit new
Site Supporter
Location
NE Tenn
Might widen the tray later. For now I just want to get it going and see how well it works. Anyone removed an exhaust tube in one?
May be a battle to get it out without opening up the tray.l have zero experience trying to remove one! So no one beat me up for my thoughts please!
But wondering if you could drill a bunch of small holes (1/8”) around both the bulkhead and end cap in the glass to break the seal and whack it with a hammer and block of wood?? More than likely the old foam will probably have a good grip on the pipe too.Possibly figure out how to twist the pipe around before the above mentioned.
Just one man’s opinion
 
The pipe bends upward in the middle of the right side of the tray to prevent back flow. There isn’t really an “easy way” to remove it. Even with the tray open. But the performance gains to be had by doing it is well worth it. Especially if this will be a surf boat, opening the tray and reinforcing the bulkhead of the 550 is highly recommended.
 

smokeysevin

one man with a couch
Site Supporter
Location
Houston
The pole/pole mount looks really good on there.

Exhaust wise, I don't have any advise becasue mine was a side exit JS not a SX but if you are going to widen the tray, it would probably be the best time to do it.

Sean
 

E350

Site Supporter
Location
Sacramento Delta
How do you reinforce the bulkhead on the 550?
I have cracks on the X2 where the engine compartment hits the tray.
I can see that happening on the 550 too. . .
 
How do you reinforce the bulkhead on the 550?
I have cracks on the X2 where the engine compartment hits the tray.
I can see that happening on the 550 too. . .
Cut the tray and reinforce it just like you would the sides. Worth it as you don’t want to stomp your foot through it on a hard landing
 
Waiting on conversion kits, introducing the girls to each other, I think they like each other..

Considering tossing the pp 550 motor back in with the baby pump and hitting the lake.

I’ve decided to run the 550 exhaust at first and see how much of a trap speed gain I get from opening the exhaust up when I do
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Location
dfw
Any flow restriction on a stock 701 pipe will result in less total power. I would not worry about it. You wont make good power without a decent pipe combined with porting and 7000+ rpm.
 
Well my primary concern is maintaining stock level performance. I love the way my stock 62t has balanced and predictable response through the power band. We will see what reducing the size of the exhaust system does.
 
Location
dfw
An un-tuned exhaust make smooth throttling but hard to get enough power out of them. The older I get the less I like riding with a good pipe.
 

E350

Site Supporter
Location
Sacramento Delta
An un-tuned exhaust make smooth throttling but hard to get enough power out of them. The older I get the less I like riding with a good pipe.
There was this whole thing about putting a chip in the Ford 7.3 PSD engine. But it seemed to me from reading the threads at Ford-Trucks.com that it could create a non-linear throttle response. And I drive on ice allot, so I was afraid of a kind of turbo effect kicking in and breaking the tires loose, so I never installed a chip.

I have been similarly afraid of adding a pipe to a jet ski engine. So, this statement makes me want to inquire about what you mean @kevbo and @SexPanther:

"The older I get the less I like riding with a good pipe."
 
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