Both Engines Limited to 9,000 RPM, WHY?

[swatski]

@AZ Native The boat looks mint, BTW. What a GREAT find!

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[Bruce]

@swatski, a fun part of MR-1 history is that the stickers on high output engines say 104.5 KW (140 BHP) while the manuals say 160 HP.

I am assuming that his sticker is correct for the 140 HP non HO MR1 that was used in earlier 230s.

I believe there also is a 75KW MR-1 variant that maxes out around 8,000 RPM.

This thread has info on various MR-1 models https://jetboaters.net/threads/does-anyone-have-detailed-info-on-the-various-mr1-versions-hp-and-impeller-questions.8478/

 

[Gym]

There are no markings on the engine or side of the boat that indicate HO. But, the recent Yamaha tech (works on jet skis not the boats) swore that it's an HO because the intakes have horn like adapters with the screens on top of them. I really don't know what I have. I don't know Yamaha's markings in 2005. I can take some pictures of the engines to post.

The Arizona Desert lakes are at maybe 1,300 to 1,400 feet. Altitude is definitely not the issue.

I hate to disagree with you but altitude is most definately an issue here. Specifically density altitude. If you do a quick calculation using your estimate of 1300 feet for your lake and add a 90 degree temperature you get a density altitude of 5147 feet. That means the engines will operate as if they are at 5147 feet altitude where there is less oxygen to burn translating to less power. I'm sure your temperatures are well in excess of 90 degrees also.

Before you pull your boat apart I would consider that whatever is happening it is affecting both engines identically. If you can run it at lower altitude or on a much cooler day that should prove this one way or the other. I doubt the previous owner swapped out both impellers with only 115 hours on the boat. I would also take a quick peak at the spark plugs and make sure they are NGK CR9EB as these engines are pretty fussy about spark plugs.

 

[swatski]

^^^^ This is it! (what @Gym said)

 

[Ronnie]

I thought I read that the Engines rev to 10k on the trailer. If so and if the trailer is at the same altitude as the water shouldn't they rev to 10k on the water as well?

 

[AZ Native]

I hate to disagree with you but altitude is most definately an issue here. Specifically density altitude. If you do a quick calculation using your estimate of 1300 feet for your lake and add a 90 degree temperature you get a density altitude of 5147 feet. That means the engines will operate as if they are at 5147 feet altitude where there is less oxygen to burn translating to less power. I'm sure your temperatures are well in excess of 90 degrees also.

Great point. As a former private pilot I should have thought of density altitude, but my DA calculator puts the altitude at more like 3,800 feet using a 90 degree temp, dew point of 60% (relative humidity about 37%) and barometric pressure at 29.82 which is pretty typical in late July and August in the early morning when we ski. Yes temps climb to 100-105 degrees by mid-day, but I'm not enough of an engine expert to know what real impact that 2,500 ft altitude difference would have on horse power or RPM's. Instinct tells me I'm not loosing 1,000 RPM over DA, maybe 100 or so.

 

[Gym]

Great point. As a former private pilot I should have thought of density altitude, but my DA calculator puts the altitude at more like 3,800 feet using a 90 degree temp, dew point of 60% (relative humidity about 37%) and barometric pressure at 29.82 which is pretty typical in late July and August in the early morning when we ski. Yes temps climb to 100-105 degrees by mid-day, but I'm not enough of an engine expert to know what real impact that 2,500 ft altitude difference would have on horse power or RPM's. Instinct tells me I'm not loosing 1,000 RPM over DA, maybe 100 or so.

I did have to throw in a guess factor for barometric pressure and relative humidity but using your figures I get 3899 feet, 4200 feet if the temp goes to 95 and 4497 if your temp reaches 100. You know better than I as to the temps you boat at. I would continue looking for other contributing factors such as the oil soaked air filters you found and possible incorrect or improperly gapped spark plugs but given the fact that both engines are experiencing the exact same results would lead me to a more global issue such as fuel or environment. Keep us in the loop.

 

[swatski]

@AZ Native As much as I was hoping for some kind of a smoking gun find here, I agree with @Gym. I bet this boat will do mid-forties at sea level ( with clean air filters, new spark plugs etc.) which is on par with expectations.

Max RPM on a trailer is irrelevant. The pumps are not loaded and the engines will hit the rev limiter with a fraction of power. (Aside from the point its not advised in the manual).

Please keep us posted!

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[scokill]

Great point. As a former private pilot I should have thought of density altitude, but my DA calculator puts the altitude at more like 3,800 feet using a 90 degree temp, dew point of 60% (relative humidity about 37%) and barometric pressure at 29.82 which is pretty typical in late July and August in the early morning when we ski. Yes temps climb to 100-105 degrees by mid-day, but I'm not enough of an engine expert to know what real impact that 2,500 ft altitude difference would have on horse power or RPM's. Instinct tells me I'm not loosing 1,000 RPM over DA, maybe 100 or so.

I would be surprised if this is the issue. We are at roughly 600 ft above sea level and on days with 100+ with zero impact. Not apples to apples but if roughly double elevation is 1000 rpm drop then 1/2 should be something and it's not.

 

[txav8r]

DA is certainly a player, even here at sea level! As far as test numbers, my boat ran 52 when new, now with two batteries, two amps, a sub, a sub enclosure, and all my shit, it doesn't. You may or may not have an issue, but I want to know what your oil level is after warm up on the water, after 5 minutes to settle and stabilize. An overfilled MR-1 can be affected, but how much is the question. Your issue here is RPM. And I agree that max rpm on the trailer does not compare to a loaded pump in the water...and also agree you shouldn't rev your engines to 10K out of the water. Find out what impellers you have. Do you have the service records? If not, if you pull the pumps, there is a part number stamped right on the base of the impeller side. These are not your impellers, but here is where it is...

 

[Marvin willis]

I see ppl talk about not being able to hit 52 when I can hit it all day long with a boat full of ppl and equipment. It doesn't plane as easy with all these fat ppl on my boat but once it planes out nothing will slow it down. Even with a boat full of ppl my wife jerks me out of the water when I slolum ski and cruises at 45 (around 9000 rpms). I couldn't be happier with any other boat. Best purchase ever! Every other boat I've skied behind I was in fear of drowning before they got me out of the water.

 

[scokill]

I see ppl talk about not being able to hit 52 when I can hit it all day long with a boat full of ppl and equipment. It doesn't plane as easy with all these fat ppl on my boat but once it planes out nothing will slow it down. Even with a boat full of ppl my wife jerks me out of the water when I slolum ski and cruises at 45 (around 9000 rpms). I couldn't be happier with any other boat. Best purchase ever! Every other boat I've skied behind I was in fear of drowning before they got me out of the water.

GPS or dreamometer? When I had a paddlewheel speedo I reached 50-52 all the time. It over estimated speed by 4-6 MPH

 

[Marvin willis]

. My speedo is almost dead on with my gps at most speeds. Wasn't even close when I got it. I adjusted it while my buddy drove with gps

 

[AZDANSX230HO]

@AZ Native I am in Arizona as well and boat down at Lake Pleasant, I have a 2008 SX230 High Output, I get up to 10,000 RPM's on a hot day with no issues, so I do not feel the DA has much to do with your boat. I would as others mentioned see if those are the stock impellers, if not somebody installed different ones for lower end power.

If you do not want to mess with pulling your pumps/impellers, I would recommend calling Brian Boell at Ultimate Watercraft Performance, he has a shop at his home in Phoenix and at his home in Lake Havasu, probably the nicest and most knowledgeable guy you will ever meet, I had him build me a race motor for a Yamaha SuperJet, that ski ripped and was extremely reliable. He builds races skis for some of the top racers in the IJSBA, and he is very fair on his rates and parts. Our boats are overgrown jet ski's, he can fix or repair anything and his work is meticulous.

His cell phone is 510-681-8196

https://www.facebook.com/Ultimate-Watercraft-Performance-556711691134419/

 

[KXCam22]

Possibly the throttles need adjustment and are not wide open when the levers hit the stops. Cam.

 

[AZ Native]

Possibly the throttles need adjustment and are not wide open when the levers hit the stops. Cam.

Thanks, that's actually the first thing I adjusted. They weren't going to the stops, but it didn't make any different with top RPM's.

 

[AZ Native]

I am sticking with the theory that you have over pitched impellers.

Your impellers should be

Impeller STBD 16.3 DEGREES 68N-R1321-10-00
Impeller PORT 17.3 DEGREES 6B5-R1321-00-00

Okay I have the pumps apart and here are pictures of the numbers and the condition (Starboard first 2, Port second 2). They sure look like factory and appear to match the numbers Bruce provided. The only flaw I see is one obvious ding in the trailing edge of the port impeller from a rock. The bearings turn free and smooth on both shafts and are tight in the housing. I also added a photo of the Port shaft that has been rubbing on white nylon bushing where it enters the fiberglass hull. I have no idea what turned the bushing blue.

Port bushing
Starboard bushing

 

[Scottintexas]

The page that Txav8r posted with the impeller numbers above was for the HO engines, it does not apply to you,

 

[AZ Native]

The page that Txav8r posted with the impeller numbers above was for the HO engines, it does not apply to you,

He did clarify these were not my boat. I researched the impeller part numbers myself for the SRT-1000D engine that I have and they match. They also match what Bruce suggested. I'm confident these are the stock and correct impellers.

BTW: this is how much oil I removed from the 2 engines today after just recently having a pro change the oil. The dipsticks now just read oil on the very tips. I also noticed what looks like a hole in the intake boxes to allow air into the oil chamber. If that's where the oil is getting into the intake it's no wonder the level needs to be kept so low.


Going to the lake tomorrow. Hopefully I'll have a little more power and top end and the oil will stay out of the intakes.

 

[bronze_10]

So in following this thread a qhestion comes to mine about the standard verses high out put mr1.... is the only different the rpm limiter that determines the overall horse power output? Could you take a non ho and change the Rev limiter to
10k and then it suddenly produces the same as the ho? And I assume the ecu is what regulates that...