MR-1 RPM

[ncnmra]

I have a 2008 212X (twin MR-1 engines).

I'm trying to hunt down why my port engine will only hit 9800 rpm, while the starboard will hit 10,000+

I noticed this issue all last year, and I had the plugs changed out before it was winterized (I know, I should have waited until the spring).

Other than plugs, what are some of the reasons for rpm loss? It seems that my port engine is slightly "weaker"; it takes a bit longer to spin up to full rpm than the starboard. I know that the impellers are different pitch, and wondering how that may effect things.

I have tried to swap the air filters between the two engines and if anything, it got worse than better. I'm tempted to try to run without air filters all together to try; but the manual strongly warns against this, as it may "cause damage".

What other things should I look for?
- Spark Plugs
- Air filter
- Fuel filters??
- Throttle cable (I have checked, it looks like its fully tight)
- Impellers?
- Compression?

Any other obvious things to check? Should I care? I rarely hit WOT either way, but I'm wondering if it may be a symptom of something else.

Do these plugs look "fouled" to you guys? It is #2 and #3 from the port engine.

 

[swatski]

Has it always been like that?
Impeller pitch has a huge impact, roughly 100-200RPM+/- for every 1mm of leading edge angle, something you could not see by eye.

 

[Murf'n'surf]

I had lost 400rpm and gained most of it back after replacing my impeller cone bearings, shaft bearings and impeller.

Sounds like your case is more impeller related. You might have dings and dents that are causing loss of rpm. Got pics of your impeller in the housing? A tight gap around the impeller is needed.

 

[bronze_10]

My 2008 sx230 has different max rpm on each engine... the port spins at 10200 and the starboard spins at 10400.... if I freshened up my impellers that might even out but they move me along juat fine.

 

[Big Shasta]

I have a 2008 212X (twin MR-1 engines).

I'm trying to hunt down why my port engine will only hit 9800 rpm, while the starboard will hit 10,000+

I noticed this issue all last year, and I had the plugs changed out before it was winterized (I know, I should have waited until the spring).

Other than plugs, what are some of the reasons for rpm loss? It seems that my port engine is slightly "weaker"; it takes a bit longer to spin up to full rpm than the starboard. I know that the impellers are different pitch, and wondering how that may effect things.

I have tried to swap the air filters between the two engines and if anything, it got worse than better. I'm tempted to try to run without air filters all together to try; but the manual strongly warns against this, as it may "cause damage".

What other things should I look for?
- Spark Plugs
- Air filter
- Fuel filters??
- Throttle cable (I have checked, it looks like its fully tight)
- Impellers?
- Compression?

Any other obvious things to check? Should I care? I rarely hit WOT either way, but I'm wondering if it may be a symptom of something else.

Do these plugs look "fouled" to you guys? It is #2 and #3 from the port engine.


View attachment 43005 View attachment 43006

They look dark to me...they should be nice and tan. But that's more of my years with cars talking. I don't remember what mine looked like out of my AR230.

Maybe a compression test to see if you have more wear on one engine. More likely it's the impeller stuff mentioned though....if you haven't pulled the impeller housings and checked/serviced them, do it before a failure. Trust me, it sucks. https://jetboaters.net/threads/impeller-bearings-trashed-lots-of-rebuild-pics-pg-6.2822/

But if you're coming that close to 10K, might not want to worry about it too much...just blast it and have fun.

 

[ncnmra]

Thanks guys. I'll pull the impeller(s) and take a look. Are there any replaceable parts that I should consider changing while the impellers are out? I'll try to take some pictures when it comes out of the water today.

I can't say for certain; but I seem to recall that when I got it in late 2014, I was able to hit 10,200 on both. I only had it for a short period though. Then, at the start of 2015 I noticed the port side at 9800, and it's been like that pretty much since.

I was hoping that the plug change would solve it, but seems it didn't.

Can you tell me; when you guys throttle up fully; do both engines respond the same? I find my port side comes up; then falls; then rises again but at a slower rate than the starboard.

 

[ncnmra]

@Big Shasta : I didn't realize that the bearing is a maintenance item. Is that documented somewhere or just good practice. I think I'll wait until the end of the season to pull the pumps. I don't want to mess something up.

 

[Speedling]

I never hit 10k
Stuck at 9800 both engines.
You just need a slight re-pitch like me.

 

[Gym]

@ncnmra. Some of your symptoms still could point to spark plugs. When you state that your rpm rise then fall then rise again sounds like plugs. The 1st pic of your plugs looks pretty carboned up to me. Before getting too deep I would consider replacing the plugs in that motor only to see if there is a change. While you have those plugs out do a compression test as you may be blowing a little oil in #2 resulting in a partially fouled plug. I would also check the spark plug gap on the plugs you take out. Someone may have dropped a plug into the spark plug hole cause the gap to close up a bit on that carboned plug.

Pulling the pumps may also show your wear rings are beginning to swell causing minor contact between the ring and impeller which would result in lower rpm and increasing wear to the impeller blades. I just replaced my wear rings this spring for that exact reason. You may notice more of a metallic rattling than usual while running on the hose while on the trailer if this is the case.

Here are some pics from my wear ring job. You can see the point of contact indicated by the corrosion spot on the inside of the ring. Before I dismantled the pump I marked the point of contact with a black sharpie. You can also see me pointing to it. If you do pull the pump check your cone bearings as @Murf'n'surf stated.

 

[ncnmra]

Thanks for all the useful advice guys! I will certainly try to change out the plugs on the port engine. It is an easy test. I wonder if the fuel stabilizer and/or ethanol fuel may play a role in the fouling. I don't think the plugs look awful, but certainly they don't look great.

 

[buckbuck]

See if the lock nuts on the throttle cable have loosened up. This is how you adjust to get full rotation of the butterfly valves.

 

[ncnmra]

See if the lock nuts on the throttle cable have loosened up. This is how you adjust to get full rotation of the butterfly valves.

I checked that. It looked to me that they were marked at the factory, and the nuts look like they are a "security" type (torx with a center point?) I suppose I could pull them back a 1/4 turn with some pliers perhaps?

Sorry wait: lock nuts? I saw some throttle stops after taking off the flame arrestors. I can see that the throttle lever is engaging the throttle to its limit. It seems like the torx "security" screws are what is keeping the butterfly valve from going any further (although it does look pretty "open" to me).

They haven't changed their position as per the factory markings (looks like a white sharpie or something).

 

[Big Shasta]

@Big Shasta : I didn't realize that the bearing is a maintenance item. Is that documented somewhere or just good practice. I think I'll wait until the end of the season to pull the pumps. I don't want to mess something up.

I learned about the bearings the hard way. After the first time, you could easily check both sides in about 2 hours. I would recommend it annually.

 

[ncnmra]

I took the boat out by myself for a quick spin yesterday. Port engine takes slightly longer to get to full RPM than starboard when throttle is applied equally to both. I was able to get both engines to about 10,000 rpm. Starboard doesn't seem to want to hit 10,200 either. Am I just splitting hairs at this point?

Let me throw something else out: how much does elevation play a role? I'm on Lake Huron: Fresh water and it is about 580' about Sea Level. Could that account for the 200-400 rpm decrease?

I also took a video of a full throttle start, I will post shortly.

 

[ncnmra]

Here is the video (not the greatest quality):

You can see that port takes a little longer to get to top RPM. In this instance port got to 9800, starboard around 9900. Normal?

 

[buckbuck]

@ncnmra we have the same boat and that is certainly not normal compared to mine. I just don't know what to suggest.

 

[ncnmra]

@buckbuck : where do you boat? I'm going to try fresh plugs first and foremost. I had my mechanic replace them last year while winterizing, but I'm not sure if he fogs or not (thinking NOT, but who knows). I'm not convinced that the plugs are in 100% top shape, maybe bad gas around here or something.

After the plugs, I may have to leave it for the season; I don't want to mess anything up and ruin the rest of our short summer.

@Big Shasta : Can the cone bearings be checked without pulling the whole pump? It looks like if I just remove the gate I would have clear access, no? It looks like if I just remove the steering assembly, I could do it without pulling the shaft out?

 

[ncnmra]

Best I can tell, port impeller looks good (nevermind the small weed)

 

[Big Shasta]

@Big Shasta : Can the cone bearings be checked without pulling the whole pump? It looks like if I just remove the gate I would have clear access, no? It looks like if I just remove the steering assembly, I could do it without pulling the shaft out?

Sure...you should be able to remove the bucket then the deflector nozzle then the cone.

http://www.boats.net/parts/search/Yamaha/Boat/2008/212X - FAT1100AG/JET UNIT 1/parts.html

 

[ncnmra]

@Big Shasta: I stayed up late reading your and @Murf'n'surf 's threads. Very good read!

I found some Honda 77 (the Yamalube Moly is harder to get here) which I will use on the shaft/spline. Did you use the Loctite on the pump parts?