587 to 720 conversion

[cholber1]

Hey all,

I have a clean 95 spi with stock 587 and runs good but was thinking about converting it to a 720. Obviously i need a 720 mpem but what else will I need? Will my exhaust work? And will it bolt right in and just align it? Any help would be great.

Thanks,
Chris

 

[AdamXP800]

I know @Matt Braley has done this conversion before

 

[cholber1]

Well i was reading up and looks like the motor plate and the driveshafts are the same so I’m thinking easy swap. Now just need to make sure wether or not i can use my 587 exhaust or have to get one for a 720. Wonder how 25hp seat of the pants will feel. Hate to do this and you really cant tell the difference.

 

[mikidymac]

You need the 720 intake carbs and exhaust.

 

[cholber1]

Well for the single carb 720 it uses a 38bn same as the 587 just main, pilot and needle are different.

 

[Matt Braley]

The 720 single carb is a SBN. It has allen bolts running through either side instead of those two nuts on the base of the earlier carbs. The 720 carb also may require a different choke and throttle cable.

The bedplates are almost the same but the 587-657X has round holes in it and the 720 ones are oval shape. You can file the older ones out if needed but it takes a while, that steel is tough.

The drive shafts a would both be about 17 inches but the 587 one would be the same diameter from the sealing area all the way back. The 720 shaft has a ridge in back and uses a different impeller boot.

I don't think you need a different MPEM. The 720 version has a little bit higher rev limit but it may not be needed. You will need the 720 impeller for sure. The swap is worth doing, the power difference is very noticeable.

 

[cholber1]

Cool thanks matt i appreciate all the info.

Chris

 

[IDoSeaDoo]

Yea, my buddy did it on a 91SP. Said it was so much fun because that hull would just slide all over. Wish I could have tried it before he sold it. He had the twin carb which pulls really well.

 

[DanSquires]

It's definitely worth the swap. The water line routing is a little different, nothing too drastic.
Here's one I did last summer, I used a 95 xp ebox and impeller

 

[cholber1]

It's definitely worth the swap. The water line routing is a little different, nothing too drastic.
Here's one I did last summer, I used a 95 xp ebox and impeller
View attachment 34019View attachment 34020View attachment 34019View attachment 34020

What exhaust did you use?

 

[cholber1]

Also was that a single or dual carb?

 

[DanSquires]

720 manifold and pipe from like a 97 or so ski, left the original waterbox and exhaust tube/outlet.
And I ran dual carbs on this ski, it's what I had laying around...

 

[cholber1]

Thanks dan appreciate the info