No Idle 9K Max RPM

[rsjohnsn]

Hi all, first time here and first time owner of a 2008 Yamaha SX230. Some background on me before we get to my issue. My wife and I used to race jet ski's back in the late '90's and I built my own engines but they were 2 stroke. I know my way around the Yamaha 2 stroke's so when I drove this new boat and it didn't idle, I thought no problem, just a little adjustment will fix this issue. Well long story short, I am lost! I purchased this boat a week ago and I have changed the plugs, oil and adjusted the throttle on the engine. I did a compression test and the problem engine has 145, 140, 145 and 145. The other engine has 195, 200, 200 and 200. This test was done on a cold engine when I was changing plugs. Problem engine also only goes to 9K rpm and the other hits over 10K. The guy I purchased the boat from said one engine is new do to a stuck fuel injector dumping fuel into the engine. He replased all 8 injectors, injector heads (?) and both ecm's. What am I looking at here? Where do I start? Thanks all

Scott

 

[Acard7]

Swap ECMs to see if the problem follows to the good engine. I would be leery to actually trust if the guy replaced both ECMs unless there were receipts to prove it. Not quite sure what you mean by it doesn’t idle? There’s also a throttle screw that’s like a T25 in this thread:

https://jetboaters.net/threads/no-wake-mode-wont-engage-adjust-throttle-stop-screw.2432/

There’s a picture of the screw I’m talking about in that thread that may be worth trying to turn. Not sure it’ll work but worth a shot. Surprised you aren’t getting any warning lights either if it isn’t running right!

 

[rsjohnsn]

I cant say 100% that he did change the ECM'S but he did give me two old one's in a box.

 

[zipper]

Is the "new" engine the problem engine? Are you sure the "new" engine is a mr-1 ho? My mr-1's turned at 10,200+. The compression looks low as compared to the other one. Lack of rpm's is usually a spark plug, easily fixed. But obviously not in your case. Compare the engine data tags. Looking for 104.5 kw.

This one is on the engine hatch.


Take it from the motor.


An this decal on the air filter cover.

 

[rsjohnsn]

No, the new engine is fine, it has 200psi of compression. Yes they are both MR-1 HO's. I am going to check later to make sure I got all the coils plugged back in and switch the ecm's to see if that makes a difference.

 

[rsjohnsn]

I worked on the boat a little today and I got my RPM back but still no idle.. I had tried adjusting the throttle to make it idle and caused my own issue. I verified that all my ignition coils were plugged in. I did not however get to swap the ECM's to see if it was the issue. I also noticed some copper rtv on the suspect engine so I may have misspoke about which engine was newly rebuilt. Now I'm not sure which it was and the previous owner doesn't know nor does the paperwork say. My cold compression is140-145 psi on the engine that is having problems and 195-200 on the good running engine.

 

[zipper]

Just trying to match up your low compression numbers with an engine. https://jetboaters.net/threads/mr-1-ho-compression.1720/
Mr-1 HO's are up around 11.9:1, which is ok, if not a bit high for your higher compression reading.

https://jetboaters.net/threads/does-anyone-have-detailed-info-on-the-various-mr1-versions-hp-and-impeller-questions.8478/

I still think one motor is not HO.

Yamaha MR-1 High Output 4 Stroke engines

This would be my first boat. What should I expect of this engine? This is Inboard engine? CAn I keep this in seawater for a season (say 4 months) before dry docking it or should I dry dock it after every use/weekend? Thanks.

forums.iboats.com

 

[rsjohnsn]

Ok, everything that I see on the motor says HO. I know that you can change the valve cover so how else can I find out? Oh and since I reset the throttle cable I am at 10k + in rpm's, pretty even with the other motor.

 

[rsjohnsn]

Just some pics of the motor with the issues.

 

[rsjohnsn]

Ok, I got the YDS software and connected everything up and my throttle valve opening and my TPS voltage was different than the good running engine so I set them the same but it still won't idle. I set them the same at idle and at full throttle. Of course the engine wasn't running so I may have to tweak it when I get to the lake. Now I'm thinking out loud but could the butterflies not be set the same?

 

[rsjohnsn]

Oh I forgot, everything else was all normal except Intake Pressure Sensor. This showed up on both engines but not sure what it is or how to fix it.

 

[rsjohnsn]

Ok, another update. I found some loose bolts on the throttle bodies to the intake. One bolt wasn't even threaded into the intake. Now that I fixed that, she idles but she idles around 12-1300. The other engine idles around 1800. With it set this way and both idle screws set exactly the same my TPS and Throttle Valve Opening are exactly the same on YDS without the engine running. Max throttle is also the same. Now to get the idle close to the same, I have to adjust the idle screw 4 full turns which then throws my TPS and Throttle Valve Opening way off from the other. How do I get the idle correct without throwing the TPS value off from the other? Does it matter?

 

[wajetter]

The manual has a very specific procedure for idle. Look it up.
Make sure evening is clean and not gunked up. All holes in the throttle bodies and hoses should be cleaned out with carb cleaner and tire and dried out.
Then, set the bypass screws to 2.5 turns out after they are turned in. Then, proceed to setting #2 throttle body to make sure it is closed. Then, tune the rest to match them closed. Only then tune in YDS

 

[rsjohnsn]

Thanks, I found the procedure. I do have a question about the process. In the directions it says to turn 1 turn, is that a 180* or 360* turn? I am assuming a 360* turn but I want to make sure. Thanks

 

[wajetter]

A turn is 360

 

[rsjohnsn]

Just wanted to make sure. Thanks

 

[rsjohnsn]

I went through the whole fuel system including pulling the throttle bodies and properly setting them up. Number 4 throttle body was completely closed at idle which definitely made a difference on how well it idled. Anyway, after setting them up properly she purrs like a kitten but only up to 1400 rpm. If I set it to match the other engine then it wants to start hanging at higher rpm's. While doing this I noticed that my timing is fluctuating from 6* to 15* at idle. The good engine idles at 5* with no fluctuating. What controls the timing? ECM?

 

[wajetter]

…I noticed that my timing is fluctuating from 6* to 15* at idle. The good engine idles at 5* with no fluctuating. What controls the timing? ECM?

How did you measure timing ?

 

[rsjohnsn]

YDIS

 

[rsjohnsn]

Ok, I swapped cam sensor with good motor and no change. I then swapped ecm with good motor and no change. I have verified that my timing should be at 5* btdc but it is hovering around 14-15* btdc. I'm afraid to ask this but for me to set the timing correctly, I have to go into the engine, correct? If so, can I do this without pulling the motor?