Top Speed <AR192>

[I_squared_r]

Yea I’m not sure I’d spend the money for the Riva sleeve. I bought it for my boat but looking back I would have spent the money elsewhere. Just don’t leave the boot in there!

Great! I will put it back together right now. I had the manifold and intercooler out in 30 min. Going to pick up the intercooler in 1 hour haha hows that for fast?

 

[I_squared_r]

What size hose comes off the intercooler? I think I saw 5/8” somewhere. I was looking for a wye fitting, but Amazon can send a tee fitting next day.

 

[d_coyne1984]

With the boat off put the throttle in the full forward position and then check to make sure the throttle assembly is hitting the stopper.

On this video from JBP on syncing throttles of the twin engine boats, you can see what to look for:

 

[haknslash]

What size hose comes off the intercooler? I think I saw 5/8” somewhere. I was looking for a wye fitting, but Amazon can send a tee fitting next day.

I used 1/2" inside diameter hose on my install https://jetboaters.net/threads/how-to-video-swap-your-sho-intercooler-to-svho. Go with the Wye fitting so the hose won't be a tight radius/kink or run a dedicated line to an extra pisser like the 195's have.

 

[I_squared_r]

With the boat off put the throttle in the full forward position and then check to make sure the throttle assembly is hitting the stopper.

On this video from JBP on syncing throttles of the twin engine boats, you can see what to look for:

Mine wasn't bad. About 2mm off the throttle stop.

 

[I_squared_r]

Went out yesterday with 3 people. Reached 7000 rpm at 39 mph. I’m going to pull the fuel pump and check the filter now that I’m at 1/2 tank of fuel.

 

[swatski]

Went out yesterday with 3 people. Reached 7000 rpm at 39 mph. I’m going to pull the fuel pump and check the filter now that I’m at 1/2 tank of fuel.

To me, it seems you have no cavitation issues because your RPM stay that low, otherwise your speed would suffer but the RPM would be hitting the rev limiter. So, that's good.

How good is your hole shot? Do you feel any cavitation/impeller slipping? Kind of like wheels spinning in mud? Or is the pump hooking up instantaneously and makes the boat jump up on plane?

My thinking is, and this is distinct from heat soak issues and IC upgrade that you are doing anyway (which is a great idea as I understand it), you may be overpropped. Meaning your impelelr's pitch is too aggressive and the engine lacks sufficient power to spin it at WOT closer to the rev limit of approx 7,800 RPM.

If that is the case (no slippage/cavitation and strong hole shot but low RPM at WOT) you may want to consider repitching the prop slightly starting on the trailing edge (it's easier and has more influence on RPM at WOT whereas leading edge has more influence on "hooking"). Because of the "progressive" pitch of these impellers, it is not always easy to find the best pitch but playing with it will at least give you some idea what is limiting. It could be fuel, but you may be getting all the fuel you need already, who knows? You may simply be running with an impeller that is "over pitched".
In that context, pitch numbers mean nothing when comparing different impellers or same eimpelelrs in different boats/skis. So you really need to test-repitch-test cycle to empiricaly dial it in, in your boat.

The good thing about being (slightly) overpitched is - there is no cavitation on hole shot and you can have tremendous pull at low speeds. If you are doing water sports that is awesome, and way more important than top speed that does not matter at all.
(as long as you are not spinning too, too low and lugging the engine but you are certainly not in danger of that, not even close, and that is rarely an issue with jet boats and impellers, can be significant issue with propped boats).
If you are not doing water sports, being pitched for low-end power will make the boat more impervious to load, no matter how many people and coolers you pack in you will be able to jump up on plane and go 35+mph, which can be way better than having a fast boat that can not get up on plane when loaded and takes 5min to reach that amazing top speed. I had two setups for my 190, and ended up always pretty much running the "power" set up that was barely 40mph with a great hole shot. Way more fun and useful that way, for me. Of course with the supercharged 192 you should be able to have a monster hole shot and 45+ top speed!

Just thinking out loud...

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[I_squared_r]

I pulled the pump and cleaned the filter best that I could. It didn’t look very dirty, but is hard to see.

I attached a photo of the impeller. It looks like OEM because I looks like the original impeller on the bench. Looks like I caught a little bag .. maybe that could contribute..

As for holeshots and cavitation. It feels fine. Nothing out of the ordinary

 

[swatski]

I pulled the pump and cleaned the filter best that I could. It didn’t look very dirty, but is hard to see.

I attached a photo of the impeller. It looks like OEM because I looks like the original impeller on the bench. Looks like I caught a little bag .. maybe that could contribute..

As for holeshots and cavitation. It feels fine. Nothing out of the ordinary

Yes, that is OEM impeller, which is the best, frankly.
The plastic bag does not help, were you able to pull the impeller and the shaft? Is it spinning smoothly in the bearings in stator segment? Any catching on the wear ring?
I would like to know what is the green arrow stuff, some twig perhaps? That could really disrupt thing if it is/was stuck between the impeller and the wear ring.
And any areas like pointed with red arrow - could be gaps, albeit it looks like the pump has been sealed nicely, 5200?

 

[I_squared_r]

I think the green arrow is corrosion. My previous post I said

"I pulled the pump and cleaned the filter best that I could. It didn’t look very dirty, but is hard to see. "

I mean that I pulled the fuel pump** I didn't pull the jet pump. I found a little dirt on the fuel filter so I will top it off with 1/2 tank of fresh gas and test for improvement. At this point, I think everything is 100% with the engine and the next step is to pull the pump and inspect for binding.

 

[djetok]

Did you look at the spark plugs?

 

[I_squared_r]

Did you look at the spark plugs?

They're new for the season. (and gapped correctly)

 

[Dean P]

What octane gas are you running? Our engines tune themselves down if not running high 93 octane.

 

[I_squared_r]

What octane gas are you running? Our engines tune themselves down if not running high 93 octane.

I don't know what the previous owner put in there. Next weekend i'm going to top off the 1/2 tank with 91 octane (manual says 90+). I'm aware that knock sensors will retard the ignition timing when lower octanes are used.

 

[swatski]

I don't know what the previous owner put in there. Next weekend i'm going to top off the 1/2 tank with 91 octane (manual says 90+). I'm aware that knock sensors will retard the ignition timing when lower octanes are used.

There are no knock sensors in Yamaha 1.8s, so if anything low octane gas is "faster". That's been tested to death and @SamCF posted somewhere where did some control runs - best speeds with 87... Which kind of makes sense. Still they advice 91 or premium in supercharged 192 I believe but it is not an absolute requirement.
But of course if that fuel is old it could be the issue!

California yamies (CARB compliant) might be different though, but I think they just have oxygen sensors and cats, no knock sensors, plus they don't sell 192/195s there anyway I believe.

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[I_squared_r]

There are no knock sensors in Yamaha 1.8s, so if anything low octane gas is "faster". That's been tested to death and @SamCF posted somewhere where did some control runs - best speeds with 87... Which kind of makes sense. Still they advice 91 or premium in supercharged 192 I believe but it is not an absolute requirement.
But of course if that fuel is old it could be the issue!

California yamies (CARB compliant) might be different though, but I think they just have oxygen sensors and cats, no knock sensors, plus they don't sell 192/195s there anyway I believe.

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I see the Yamaha parts diagram shows a knock sensor. See below part #21

Yamaha Boat 2014 OEM Parts Diagram for Electrical - 2 | Partzilla.com

Buy OEM Parts for Yamaha Boat 2014 Electrical - 2 Diagram

www.partzilla.com

I’m confused with the octane ratings for the AR192 because everyone seems to have a preference. I found an owners manual online and it says 90+ octane, but some people report best results with 87. That’s unusual because the manufacturer typically designs the combustion chamber for best efficiency and burn for a particular octane. Years ago I read a paper on speed flame propagation in Otto cycle engines. I’m struggling to remember, but the combustion ratio is a small factor in octane selection. Ultimately, the flame pattern needs to be timed to coincide with a particular piston angle. On the other hand, empirical data seems to suggest that engines run best when run lean and deto. Some of my best runs was before I melted a piston unless this topic has been beat to death before.. and 87 octane is okay.. I have no problem with saving money.

 

[Dean P]

There are no knock sensors in Yamaha 1.8s, so if anything low octane gas is "faster". That's been tested to death and @SamCF posted somewhere where did some control runs - best speeds with 87... Which kind of makes sense. Still they advice 91 or premium in supercharged 192 I believe but it is not an absolute requirement.
But of course if that fuel is old it could be the issue!

California yamies (CARB compliant) might be different though, but I think they just have oxygen sensors and cats, no knock sensors, plus they don't sell 192/195s there anyway I believe.

Is this just with the aspirated Yamaha engines? I have never heard of low octane fuel outperforming a higher octane built engine.

I have noticed a difference when running lower octane with my (supercharged) Rotax engine.

 

[swatski]

On the other hand, empirical data seems to suggest that engines run best when run lean and deto. Some of my best runs was before I melted a piston unless this topic has been beat to death before.. and 87 octane is okay.. I have no problem with saving money.

I would think you would be most definitely safe running on 87 as that is what most SHO and SVHO users do anyway, based on my reading on the topic.

I don’t know about that knock sensor, I know from RIVA and MapTune tuners that Yamaha engines do not have the capability to retard timing based on low octane/ knocking. Unlike all new BRP engines. Apparently.

I may be incorrect there are no knock sensors, but I am pretty sure that the ECUs do not adjust timing, unlike for example Toyota/Lexus engines can do.

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[I_squared_r]

I found a 2013 AR192 owner's manual and says:

Recommended fuel:
Regular unleaded gasoline with a minimum octane rating of 86
(Pump octane number) = (R + M)/2
90 (Research octane number)

The manual is oddly written. The pump octane number is what the US uses and it's the average of research and motor octane numbers.. In this case is 86 octane. I can see why performance would drop if someone thought 93 octane. I have my fingers crossed for next weekend.

 

[SamCF]

SHO runs best on 87 octane 10% ethanol. SVHO requires 91 or higher. The supercharged engines do run a knock sensor.