losing power somewhere 701sj

[ryan_march]

have had this issue for a little while. i apologize for the long post. I have a 90 sj with 701, b pipe, ada head, etc. few friends rode it and thought it was a stock ski... obviously something wrong. did a wot speed test today in completely flat water, i was only getting 25mph out of it. i couldn't stop the bow from jumping up and down constantly. Again, completely flat water where i should just be cruising right along. And i was doing everything i could to try to get it to stop and couldn't. Playing with the throttle i was able to get it a little under control for a few seconds and got a little closer to 30mph. so im missing a lot of power in the top end but im also missing in the low end. I've ridden other sj's with pretty much the exact same setup that feel way more powerful in the low end then mine. I did a compression test recently and it was 140 and 145. I contacted the person i bought the ski from and he is not sure what size domes are in it so im not sure what my compression is supposed to be. I'm going to do another compression test tomorrow to see if im losing compression, also going to do a test to see if my coil wires are shot. Other ideas of what the hell is going on would be greatly appreciated. Still new to skis so any help would be awesome. Thanks!

 

[Dorny119]

I wouldn't base power off of WOT test if you can't get the ski to stop porposing. I'm not sure what your experience level is, but a lot of people have trouble keeping the nose down at first, which will definitely cause your top speed to be very low.

As far as your low end power goes, your pump has so much to do with this. You could have bad wear ring clearance, bent/broken stator vanes, or your prop might be trash.

 

[mikidymac]

If your compression tester is good and reliable then you have something really wrong. A stock head will give you 150 psi on a good engine so if you are at 145 with a aftermarket head something is not correct.

 

[SXIPro]

The HF comp testers notoriously run about 20-25 lbs under 'reality'

 

[ryan_march]

Did another compression test. I guess I messed it up the first time. Idk how. But now I have 150 in both cylinders. Took apart my jet pump and found some things cracked. Pump shoe, the pump itself, just lots of weird poop. I will post pics tomorrow or Friday. Thanks for the reply’s so far

 

[mikidymac]

150 is still low for an AM head. Stock is 150. You might want to pull the head, take a look at the cylinders, replace the o-rings and get the cc number off the domes so you know what it should be.

 

[Req]

150 would be about right if he is using the short shank on the compression tester. You need to use the length that corresponds with the plug length. AM heads use ES (extended shaft) plugs, if you use the short shaft you get an incorrect reading about 20 psi low due to the added volume.

 

[ryan_march]

Some stuff I found when digging through getting to my impeller. Gonna change the wear ring since I’m here. Have to figure out the pitch on the prop. Prop says 6 3v. Not sure what that means. Any suggestions what to do with all this? What to replace with? I ride surf so not looking for top speed

 

[Req]

Wow, you got a real mess on your hands. It looks like the prior owner was having some pump alignment issues and said screw it, ill clearance where it doesn't fit.

I ended up having to go over a ski like this as well. Not the exact same issues but a total willingness to licorice it up so dude could ride. If he did this here he did it elsewhere. I would pull every component out of the hull and inspect it before I put it back together.

I found wires twisted together with electrical tape, fiberglass that was delaminating on the holds, totally butchered the round nose pole to make it fit, butchered the hood mod, butchered the bracket, butchered the bond line trim, etc.

 

[ryan_march]

Wow, you got a real mess on your hands. It looks like the prior owner was having some pump alignment issues and said screw it, ill clearance where it doesn't fit.

I ended up having to go over a ski like this as well. Not the exact same issues but a total willingness to licorice it up so dude could ride. If he did this here he did it elsewhere. I would pull every component out of the hull and inspect it before I put it back together.

I found wires twisted together with electrical tape, fiberglass that was delaminating on the holds, totally butchered the round nose pole to make it fit, butchered the hood mod, butchered the bracket, butchered the bond line trim, etc.

Ya. I’ve been through more than half this ski already. Air leak issues, start and stopping issues, and ya everything has been poorly done on this ski. Sucks but nothing I can do about it now.

 

[ryan_march]

150 would be about right if he is using the short shank on the compression tester. You need to use the length that corresponds with the plug length. AM heads use ES (extended shaft) plugs, if you use the short shaft you get an incorrect reading about 20 psi low due to the added volume.

The l length I was using was just a tad shorter than my plugs

 

[ryan_march]

Did some research and found that the markings 63v means 13/16 pitch. Can someone confirm this? Don’t know much about props, is this a good pitch for surf riding?

 

[Dorny119]

Replace that shoe with an aluminum shoe, new wear ring (gap looks pretty big), align properly, and buy a 9/15 hooker (I use this prop for everything from boat chasing to surf to rec riding)

 

[ryan_march]

Replace that shoe with an aluminum shoe, new wear ring (gap looks pretty big), align properly, and buy a 9/15 hooker (I use this prop for everything from boat chasing to surf to rec riding)

Alright thanks

 

[ryan_march]

Update: took apart my pump, thinking my wear ring was shot. Also wanted to take a better look at my impeller. Took everything apart to find my 2 bearings were both completely seized up. New bearings and seals came in today. Putting all back together tomorrow and hopefully she’ll rip!

 

[ryan_march]

So, went on the test ride td. Power seems to be there now, however the porpoising issue was not resolved. But I think I resolved the power issue cause it felt pretty good. Will do a speed test later. Any opinions on how to get it to stop porpoising? I don’t believe it’s my fault the way I’m riding. Gonna try putting shims in the rideplate to put some more pressure on the nose