Sx192 low speed at WOT

[zachyam]

2013 sx192. We first got on the water and cruised around topping out at 42 with 7 of us and a baby, very little gear, half tank of gas,. Once we got to tubing it dropped to about 32 at WOT, and lost a lot of speed in turns as usual. But after about an hour or so the boat wouldn't go over 20mph, barely on plane if not completely. This winter I did the ribbon delete and the svho intercooler with 2 independent outlets. Initially it seemed just like heat soak but I've upgraded the intercooler. My next thought is removing the airbox to see if it is getting choked out of air. I know I need new spark plugs but I don't think this really sounds like bad plugs. Very clean lake, only thing I've ever sucked up was my own rope a few years ago. 85 water 85 air, all 3 pissers flowing good with cool water coming out, underneath all looks brand new except some silicone missing in the tube and grate. Thoughts? Suggestions?

If I can't get it figured out the wife wants to go back to some sort of V8 to sling the kids around again but I've got dreams of surfing without the malibu budget, and I really love the all around versatility, size within our private lake restrictions, and easy maintenance of my yamaha

 

[jgourlie]

@zachyam take the air filter right out and let’s us know the results and also check your supercharger wheel if it spins both ways?

 

[zachyam]

@zachyam take the air filter right out and let’s us know the results and also check your supercharger wheel if it spins both ways?

I'm running right at 7k rpm but I will have to check the supercharger wheel. Thanks, I'm planning on putting a BOV on when my boat budget is replenished

 

[OrangeTJ]

What is the max rpm of the engine? If you are hitting that rpm, your issue is almost certainly not with anything to do with your engine and it won't be fixed by messing with the air intake or anything else like that. If you are getting max rpm, the issue pretty much has to be on the propulsion end, either cavitation or the reverse bucket not pulling all the way up. If you are not getting max rpm and you don't have fresh sparkplugs in it, that should be your first stop.

 

[Chief]

One time i had my passengers and gear in the back of the boat and i couldn't get on plane till i moved people forward, then no problem after that.

 

[Zizzou 192]

Motor, pump, clean hull. That’s all there is.

Rpm should top out at 7800.
Agree totally with changing plugs first, the 1.8’s are hard on plugs and that is probably the #1 reducer of top speed.

After that see if the air filter is not soaked with overfilled oil, then check the throttle cable to make sure it is adjusted to open the throttle all the way to the stop.

Next up is the pump. Make sure it is perfectly clean. No tiny wood chips, grass, etc. Check the reverse bucket to make sure it is not partially blocking the nozzle. Check wear ring clearance and make sure impeller is not dinged up. After that you can check the pump sealant.

A cleaned and waxed hull is good for a few more mph as well.

When the above is perfect, and the water is calm, no wind, Bimini down, no passengers, a stock 192 should make it to 49mph.

 

[zachyam]

One time i had my passengers and gear in the back of the boat and i couldn't get on plane till i moved people forward, then no problem after that.

I moved wife and baby up front and that didn't help.

 

[zachyam]

What is the max rpm of the engine? If you are hitting that rpm, your issue is almost certainly not with anything to do with your engine and it won't be fixed by messing with the air intake or anything else like that. If you are getting max rpm, the issue pretty much has to be on the propulsion end, either cavitation or the reverse bucket not pulling all the way up. If you are not getting max rpm and you don't have fresh sparkplugs in it, that should be your first stop.

Around 7100-7200. Never have I ever hit the 7600-7800 I've heard about. Plugs are ordered and will pull the filter box when I am able to get time to work on it and report back. Thanks

 

[zachyam]

Motor, pump, clean hull. That’s all there is.

Rpm should top out at 7800.
Agree totally with changing plugs first, the 1.8’s are hard on plugs and that is probably the #1 reducer of top speed.

After that see if the air filter is not soaked with overfilled oil, then check the throttle cable to make sure it is adjusted to open the throttle all the way to the stop.

Next up is the pump. Make sure it is perfectly clean. No tiny wood chips, grass, etc. Check the reverse bucket to make sure it is not partially blocking the nozzle. Check wear ring clearance and make sure impeller is not dinged up. After that you can check the pump sealant.

A cleaned and waxed hull is good for a few more mph as well.

When the above is perfect, and the water is calm, no wind, Bimini down, no passengers, a stock 192 should make it to 49mph.

I maxed out at WOT arround 7100-7200. Throttle stop was adjusted in the winter with maintenance, checked bucket and impeller. No bimini on, the wife hates it, just aftermarket tower with a wakeboard. Hull got a serious 2 coat of wax just before the last outing, it's like butta... I'm going to do plugs, take off filter box off, and order a wet wolf AAT or word cone (recommendations, dont want L13 if I can get same performance for half the cost) and see what happens, while I'm down there I'll clean up the old grate sealant. I'll report back in a couple weeks. Anybody have a recommendation on regular silicone or what? I saw where someone bondo'd and sanded but I don't have that kind of time. Thanks guys

 

[tdonoughue]

From what you described, I would be surprised if it were only plugs. Plugs may be responsible for your delta between 7200 and 7800, but not your max 20 mph. That slow degradation sounds like you were losing silicone in the pump and started to have more and more cavitation and therefore less and less speed. Do the plugs (you do want that last 600 rpm), but I bet it is the silicone fix that will really do it for you.

 

[steve0617]

Altitude where you boat? Even brand new, my 19 AR195 at 5800’ has never exceeded 6800rpms.

 

[zachyam]

Altitude where you boat? Even brand new, my 19 AR195 at 5800’ has never exceeded 6800rpms.

Elevation is about 950ft.

 

[zachyam]

Since a lot of these threads usually don't post results, I figured I would.
With the advice from SamCF, I drilled some large holes in the strainer. I also replaced plugs and put fresh gas in, and removed the airbox, which the filter was sucked up against the inlet. So the wife and I took it out to watch fireworks on the lake, before the sun went down I took it WOT. 88air 86water 2 people half tank of gas, medium lake chop 7650max rpm. This thing flat-out flied. 51mph, holeshot like a rocket, wife said it kind of scared her. Next day (July 5, very busy) 95 air 88 water full tank of gas, 7 people total, heavy wake, 45 before we put the tube out. Once 3 person lay-on tube was out I never touched WOT (for safety reasons) and this thing slung the kids about every 200ft, had to keep stopping to pick a kid or 2 up. Cavitation on hole shot when the large 3 person sit-in tube was hooked up. If I eased on the throttle it was fine, just a lot of drag from the tube is all.
Also noticed the return of heatsoak after about 1.5hrs of continuous tubing but it only noticeable by 2-3mph, we stopped in a cove and swam for about 30 mins, got back in and was good for the next few hours

 

[steve0617]

Excellent results! Did you do the sealant of the tunnel too as your previously said you were going to?

 

[zachyam]

Excellent results! Did you do the sealant of the tunnel too as your previously said you were going to?

I did not. Waiting on a tube or marine grade silicone sealant to come in.

 

[tdonoughue]

If the air filter was sucked in like that, I bet it was dirty or something (oil?) and was choking you out...

 

[zachyam]

If the air filter was sucked in like that, I bet it was dirty or something (oil?) and was choking you out...

I would agree.. some oil residue on airbox

 

[jet boat joe]

Since a lot of these threads usually don't post results, I figured I would.
With the advice from SamCF, I drilled some large holes in the strainer. I also replaced plugs and put fresh gas in, and removed the airbox, which the filter was sucked up against the inlet. So the wife and I took it out to watch fireworks on the lake, before the sun went down I took it WOT. 88air 86water 2 people half tank of gas, medium lake chop 7650max rpm. This thing flat-out flied. 51mph, holeshot like a rocket, wife said it kind of scared her. Next day (July 5, very busy) 95 air 88 water full tank of gas, 7 people total, heavy wake, 45 before we put the tube out. Once 3 person lay-on tube was out I never touched WOT (for safety reasons) and this thing slung the kids about every 200ft, had to keep stopping to pick a kid or 2 up. Cavitation on hole shot when the large 3 person sit-in tube was hooked up. If I eased on the throttle it was fine, just a lot of drag from the tube is all.
Also noticed the return of heatsoak after about 1.5hrs of continuous tubing but it only noticeable by 2-3mph, we stopped in a cove and swam for about 30 mins, got back in and was good for the next few hours

What kind of boat do you have?