2015 AR192 Performance Question

[dmmoss1]

Looking for a little advice! New 2015 Yamaha AR192 owner here. Took the boat out last week for the first time, seemed to run fine. Had 4 passengers, probably right at 600 pounds with passengers and gear. Full tank of gas, fresh water temp was around 78F. Boat cruised for 25 minutes one way, twice at 30mph. Didn’t seem to want to go much faster. Didn’t think much of it, it still seemed to do well.

Took it out this past weekend, and again would cruise at or just under 30mph. Stopping for an hour or two to enjoy the water. Then once we tried to tube, it would only go about 12mph. RPM’s were around 6500.

Last data point: we were headed back to the trailer and again, going around 12mph. About 3/4 of the way, felt a surge of power and topped out around 25mph.

Checked the impeller this afternoon, and it seems fine to me. I’ve never owned a jet boat, only outboards. Picture is attached of impeller.
Any tips or ideas on where to start? I love the layout and everything else, just need to get the power figured out.

 

[Hot2Go]

I assume when you had the issue prior to tubing you then made your way back to the trailer? Or did it fix itself and then go back to going 12mph again?

Either way guessing you sucked something up in the pump and the cavitation stopped you from going any faster. It can be a small twig that gets stuck in the impeller that will cause issues. Usually there is vibration when you suck something up, and like the symptoms you described, high RPMs but low MPHs will persist. I'm guessing when you were on your way back it dislodged finally and that is why your speed came back up.

Assuming this is the supercharged 1.8? How many hours are on the boat and if it is supercharged when was the last service on it and are you using 91 octane fuel only?

 

[dmmoss1]

I assume when you had the issue prior to tubing you then made your way back to the trailer? Or did it fix itself and then go back to going 12mph again?

Either way guessing you sucked something up in the pump and the cavitation stopped you from going any faster. It can be a small twig that gets stuck in the impeller that will cause issues. Usually there is vibration when you suck something up, and like the symptoms you described, high RPMs but low MPHs will persist. I'm guessing when you were on your way back it dislodged finally and that is why your speed came back up.

Assuming this is the supercharged 1.8? How many hours are on the boat and if it is supercharged when was the last service on it and are you using 91 octane fuel only?

Yes was headed back to the trailer when it seemed to “dislodge”. I’m guessing there’s not an easy way to check for something stuck in the system? I removed the clean out port, and felt for any obstructions.

It was running “fine” the first part of the day. Not in the 40’s, but I assumed that was ok due to the extra weight. Then once it was cranked to tube, I couldn’t get over 12mph. Tried that for a little bit, then parked and let everything rest. Packed up and headed back after that issue. Yes when headed back to the dock, it surged in power.

Yes it’s the supercharged 1.8L. The tank was full when I got it, I’ll fill up with 91 to be sure that’s covered. That’s a good, simple thing to eliminate.

Thank you for the help so far!

 

[Hot2Go]

If you checked the cleanout port and didn't feel anything then the loss of power is confusing, and I assume you didn't have any check engine lights too? Any time I had loss of power it was either something lodged in the impeller, or the one time I left the plugs out (lol).

If I had any issues with power beyond cavitation I would definitely check oil level and air filter. I always changed my spark plugs every season so never really worried about that. Supercharged motors will need the 91 octane fuel for sure though!

I know some on here modded their SC engines on other threads with a ribbon delete and an intercooler to reach 49-50mph.

 

[dmmoss1]

If you checked the cleanout port and didn't feel anything then the loss of power is confusing, and I assume you didn't have any check engine lights too? Any time I had loss of power it was either something lodged in the impeller, or the one time I left the plugs out (lol).

If I had any issues with power beyond cavitation I would definitely check oil level and air filter. I always changed my spark plugs every season so never really worried about that. Supercharged motors will need the 91 octane fuel for sure though!

I know some on here modded their SC engines on other threads with a ribbon delete and an intercooler to reach 49-50mph.

Yeah I have spark plugs on order and will change those tomorrow. I’ll check those other items as well, weather permitting. I’m also going to drain the fuel manually, just to be sure…and I’ll confirm it’s filled with 91. I’m hoping something did dislodge when I felt the increase. Also, no check engine light.
I think these are good first steps, and hopefully will get better performance this weekend.

 

[Hot2Go]

Yeah I have spark plugs on order and will change those tomorrow. I’ll check those other items as well, weather permitting. I’m also going to drain the fuel manually, just to be sure…and I’ll confirm it’s filled with 91. I’m hoping something did dislodge when I felt the increase. I think these are good first steps, and hopefully will get better performance this weekend.

I wouldn't necessarily say you need to drain the fuel, I'd get an additive with an octane booster and just fill it up with 91. It should be fine then.

 

[dmmoss1]

I wouldn't necessarily say you need to drain the fuel, I'd get an additive with an octane booster and just fill it up with 91. It should be fine then.

Appreciate all the helpful information!
just curious, from the limited views in the pictures, did you see any issues with the impeller area? It all looked pretty smooth/straight to me, but figured I’d check with someone with more experience.

 

[Hot2Go]

Appreciate all the helpful information!
just curious, from the limited views in the pictures, did you see any issues with the impeller area? It all looked pretty smooth/straight to me, but figured I’d check with someone with more experience.

Your impeller looked just fine to me as well!

 

[FSH 210 Sport]

To be clear the air temperature was 78° and you were in freshwater correct?
What is the altitude you are boating at?
What are the maximum RPMs you’re seeing?

 

[dmmoss1]

To be clear the air temperature was 78° and you were in freshwater correct?
What is the altitude you are boating at?
What are the maximum RPMs you’re seeing?

This was a freshwater lake and the water temp was between 78-80 on the depth finder. Air temp was, probably closer to the 80-82 range. Elevation of that lake says 840'. Max RPM's if I remember correctly were between 6100-6400, but I wouldn't bet my paycheck on those exact numbers. I'll pay more close attention to those next time I'm out, as I didn't regularly look at this. I'm going to test again with fresh plugs and better fuel either Friday or Saturday hopefully.

 

[FSH 210 Sport]

Okay you’re way off on your rpm’s … they should be in the 7400 range.

First thing I’d check is the super charger clutch, pull the intake off and make sure the wheel only spins one direction. Now typically rpm’s will be limited to 5500 rpm if the SC clutch is broken and the wheel will move both directions. Make an effort on this to make sure the wheel won’t spin in both directions.

Next make sure that all the air ducts are fully seated and secure, physically do this do just look at it, the ducts going to and from the SC and to the intercooler and from the intercooler to the intake can come loose and leak boost pressure.

Next check your oil level to make sure it’s not overfilled.

Check that your filter is clean.

Your fuel could be lacking a bit but I don’t think you need to drain it unless the engine is pinging.

Changing the spark plugs is a great move, make sure you gap them to spec before installing.

 

[dmmoss1]

Okay you’re way off on your rpm’s … they should be in the 7400 range.

First thing I’d check is the super charger clutch, pull the intake off and make sure the wheel only spins one direction. Now typically rpm’s will be limited to 5500 rpm if the SC clutch is broken and the wheel will move both directions. Make an effort on this to make sure the wheel won’t spin in both directions.

Next make sure that all the air ducts are fully seated and secure, physically do this do just look at it, the ducts going to and from the SC and to the intercooler and from the intercooler to the intake can come loose and leak boost pressure.

Next check your oil level to make sure it’s not overfilled.

Check that your filter is clean.

Your fuel could be lacking a bit but I don’t think you need to drain it unless the engine is pinging.

Changing the spark plugs is a great move, make sure you gap them to spec before installing.

I appreciate the info! Most of those were on my list of things to do/check this week in the evenings after work, but I'll check the things you mentioned. I'm decent with mechanical fixes, just have to learn this new system and then start eliminating possibilities.

 

[FSH 210 Sport]

I appreciate the info! Most of those were on my list of things to do/check this week in the evenings after work, but I'll check the things you mentioned. I'm decent with mechanical fixes, just have to learn this new system and then start eliminating possibilities.

It’s all about having the correct rpms, speeds are secondary. I operate my boat at high altitude so I’ve had to have my impellers repitched to get the rpms up due to hp loss from high density altitudes. Once you get the rpm’s correct then you start looking at the pump and the impeller. From the pics the impeller to wear ring gap looks good, it should be .014” to .0177”, the leading edges of the impeller all look good and I cannot see any bad marks in the wear ring.

 

[dmmoss1]

So to update you two helpful boaters, here’s what I’ve found so far. The oil seems good, maybe slightly higher. So I may look at pumping a little bit out tomorrow. New spark plugs are gapped and installed. Air filter looked clean.

The biggest thing I found however, was taking apart the air intake into the supercharger intake to test the uni-directional spin of the supercharger blades. The blades did spin one direction, and wouldn’t spin the other direction when reaching in. However, the air hose that feeds the supercharger was pretty much hanging off the housing. It had a visible gap, and the SC air intake hose came off by barely moving the air filter housing. I’m thinking this could be some/most of the problem? Any input into that?

I haven’t had a chance to test on the water. I have confirmed everything cranks and runs under a garden hose. Engine running, then water; water off, then engine off.

 

[FSH 210 Sport]

I don’t think the hose being off the intake side is going to cause an issue. The output side would be the real problem.