Little help - Missing RPMs

[J-RAD]

Hi folks,

I just made it out for the second time this season and noticed a change in my boats performance.

Here's the deal. Beginning 3rd season with the boat, so I'm pretty familiar with he way the boat and it's capabilities. The boat performs perfectly normal in every aspect except for one thing. I'm missing about 1k RPM on the top end. In fact I never would have noticed an issue if I hadn't gone WOT.

During our first outing a few weeks ago we had some smooth water, so I went WOT for a bit and was a bit disappointed as I only hit 40MPH. Which is a few (maybe 5) MPH down from the my top speed. I didn't read much into it, didn't even check RPM...

Today, I decided to attempt a similar test. We had a few more bodies in the boat, but the best it would do was 36MPH at 6500ish RPM. I'm certain I'm missing a significant amount of RPMs from my typical. I'm running at 4,200 elevation

I did a little trouble shooting, checking the obvious.

1. Impellers are pristine and clear of debris
2. Hull is clean
3. Both throttle cables are properly adjusted and reaching the stops on the APS.
4. Changed the oil this spring. 4 quarts came out and 4 went back in each engine. Dipstick shows its st the proper level
5. Spark plugs are new with the appropriate NGK plugs. Changed after first seasonal start and oil change...
6. No warnings
7. No overheating
8. Water coming from pee holes
9. I was using the Hydrophase Ridesteady in RPm mode while cruising. I had the throttles fully engaged and the system asking for more... I did reinstall the nodes after the RSI radio interference repair.

It is my first year doing the seasonal maintenance... but pretty confident it was done correctly... I'm a fairly handy guy.

What do you think's happening?

 

[Jgorm]

If it's the mr1, it's probably #3 missing. My waverunner does this with low compression on 3. It will run 50mph, then 42mph when that cylinder is missing. Check the compression.

 

[Gym]

@J-RAD I see you're running a 2016 AR-240. Are both engines running low rpm or just 1 side? When you installed the new plugs did you check the gap on all the plugs before installing? I check each plug for proper gap and found some of my plugs came out of the new packaging with different gap. The next thing I would check is the air filters. Even if you find them clean try running without them.

What was the outside air temperature during the run in question. If both your engines are running lower than normal it could be a "density altitude" issue. For example: at your elevation of 4200 feet with an outside air temp of 70F, an air pressure of 28.50hg and a dew point of 55F your density altitude would be 7714 feet. This means both you and your boat engines are breathing air that would normally be found at 7714 feet above sea level. Your engine computers will adjust fuel/air mixture to accommodate some of this but it only has a certain range before performance begins to drop off. If only one of your engines has low rpm it's not a density altitude issue. Check the easy stuff first.

 

[J-RAD]

@J-RAD I see you're running a 2016 AR-240. Are both engines running low rpm or just 1 side? When you installed the new plugs did you check the gap on all the plugs before installing? I check each plug for proper gap and found some of my plugs came out of the new packaging with different gap. The next thing I would check is the air filters. Even if you find them clean try running without them.

What was the outside air temperature during the run in question. If both your engines are running lower than normal it could be a "density altitude" issue. For example: at your elevation of 4200 feet with an outside air temp of 70F, an air pressure of 28.50hg and a dew point of 55F your density altitude would be 7714 feet. This means both you and your boat engines are breathing air that would normally be found at 7714 feet above sea level. Your engine computers will adjust fuel/air mixture to accommodate some of this but it only has a certain range before performance begins to drop off. If only one of your engines has low rpm it's not a density altitude issue. Check the easy stuff first.

Thanks @Gym I'll check the filters and plug gap. I was on my home lake and have never noticed such limited performance. The air temp was mid 80's, temp has never caused such a noticeable effect in previous seasons. I have the RIVA spacer ribbon delete and the dealer here sells the boats with impellers pitched for altitude. I was running with the Ridesteady active, so engine RPM was being synced. It's possible the lowest performing engine's RPM was being matched.

I'm planning to head back out this afternoon, I'll try tapping the plugs prior and hopefully that will solve the issue.

 

[J-RAD]

If it's the mr1, it's probably #3 missing. My waverunner does this with low compression on 3. It will run 50mph, then 42mph when that cylinder is missing. Check the compression.

It's a '16 AR240 with 1.8's

 

[haknslash]

Can you try to unplug or by-pass Ridesteady then test the boat? It shouldn't have an affect but let's rule it out first.

 

[J-RAD]

Can you try to unplug or by-pass Ridesteady then test the boat? It shouldn't have an affect but let's rule it out first.

Should be as easy as disconnecting the stock wires from the nodes and plugging it back into the APS. The starboard connector is just a bear to unplug, due to ther fact the release latch is on the back side pinned up against the sidewall of the engine compartment... Pain in the arse to remove...

 

[Gym]

Thanks @Gym I'll check the filters and plug gap. I was on my home lake and have never noticed such limited performance. The air temp was mid 80's, temp has never caused such a noticeable effect in previous seasons. I have the RIVA spacer ribbon delete and the dealer here sells the boats with impellers pitched for altitude. I was running with the Ridesteady active, so engine RPM was being synced. It's possible the lowest performing engine's RPM was being matched.

I'm planning to head back out this afternoon, I'll try tapping the plugs prior and hopefully that will solve the issue.

Ok @J-RAD. When I plug in the 80 degree temp I get a density altitude of 8319 feet above sea level. You still haven't mentioned if the RPM loss is affecting both engines or just one. My density altitude theory is just that, a theory but it could be a valid cause if it's affecting both engines equally. There may be other causes as have been mentioned.

 

[J-RAD]

Ok @J-RAD. When I plug in the 80 degree temp I get a density altitude of 8319 feet above sea level. You still haven't mentioned if the RPM loss is affecting both engines or just one. My density altitude theory is just that, a theory but it could be a valid cause if it's affecting both engines equally. There may be other causes as have been mentioned.

I did vaguely address the fact that both engines were being effected equally but due to the fact my Ridesteady speed control was synchronizing both engines RPMs to one another in RPM mode, I couldn't say for certain that it wasn't just one engine lagging and the other being matched by the Ridesteady. We were on our way back to the dock so I didn't have a chance to test them independently. I certainly will next time I'm out.

 

[J-RAD]

Checked plugs and gapped to spec and oil at proper levels. Ran without the Ridesteady active and whatever it is, it seems to be both engines affected which could point to environmental. However, I'm running on home waters and similar conditions to previous seasons and don't recall ever experiencing such poor top end performance. I'm topping off the batteries to see if that has something to do with it. I got a couple "Engine Comm" errors last outing that popped up for a split second and were goin gone. I know these things get glitchy when charges are low (readings was 12.3V). Beyond that...?

 

[J-RAD]

So after talking to the dealer on a couple of suggestions.

First suggestion was to change spark plus again and check the gaps. Results: the problem still persisted.

The next suggestion was to check the air filters. Upon checking the filters seemed to have become saturated with oil and. Suggesting I'd over filled the oil during servicing this spring. Oil was always below the higher mark on the dipstick and I attempted to put the same amount removed back in, but these engines seem to sensitive to any over filling. I removed enough oil to bring it down to the midway point between the 2 markings on the dipstick and purchased new air cleaners. Results: RPM was restored back to 7k-ish and we were able to run in the low 40's with 4 adults 2 kids, full tank and bimini up. Performance felt back to where it should be.

 

[haknslash]

Glad to hear @J-RAD !


.....But what everyone really wants to know is which country did Spain get replaced with???!

 

[J-RAD]

Glad to hear @J-RAD !


.....But what everyone really wants to know is which country did Spain get replaced with???!

Lol!

 

[DBamaC]

I came across this old thread while looking for a solution to an issue I had all last year. I haven't had my boat in the water yet this year, but all last year my 192 ran with low RPMs. It was really bugging me. I tried changing the plugs, checked my impeller...all the regular stuff. Interstingly, last year is the only time I didn't change my own oil...it was in for an issue so I just let them do it. I'm going to try to do my service this weekend. May overfilled oil is my problem! It'll kind of piss me off, but at least I'll have an answer...finally!

 

[J-RAD]

I came across this old thread while looking for a solution to an issue I had all last year. I haven't had my boat in the water yet this year, but all last year my 192 ran with low RPMs. It was really bugging me. I tried changing the plugs, checked my impeller...all the regular stuff. Interstingly, last year is the only time I didn't change my own oil...it was in for an issue so I just let them do it. I'm going to try to do my service this weekend. May overfilled oil is my problem! It'll kind of piss me off, but at least I'll have an answer...finally!

Give it a shot. Check those air filters, that will be the most telling sign.

 

[DBamaC]

A little oil in the filter...not so much that I’d have thought it would make a difference. Went ahead and replaced the air filter with an aftermarket.

Between a 1/2 and a full quart too much oil in the engine. That why I usually service it myself. I hope that this will find me my missing rpm’s

 

[Bmann87]

A little oil in the filter...not so much that I’d have thought it would make a difference. Went ahead and replaced the air filter with an aftermarket.

Between a 1/2 and a full quart too much oil in the engine. That why I usually service it myself. I hope that this will find me my missing rpm’s

Hey there! What was the end result on your AR192, I have these identical issues. Did you ever find out what was causing it?

 

[FSH 210 Sport]

Hey there! What was the end result on your AR192, I have these identical issues. Did you ever find out what was causing it?

Sorry to tell you this that guy has not been around since June of 2021….

 

[DBamaC]

Strangely enough, I decided to come by the forum today and found someone had asked me a question. It ended up being the fouled air filter. the Yamaha filters are a ridiculous price so I installed an aftermarker cone filter. No problems since.