" rpms limited in water"

[Stuart Bicknell]

Hey Everyone. I have a 2008 212ss and I can't get full revs on the Port side engine whilst in the water.

@Speedling has been helping me try and solve the problem. So i get full revs on the starboard engine in the water and out. Port side, I can only get about 8000 rpm in the water. I took the boat out today and I got full revs 11000 on both.

We are guessing Impeller issue!! But I'm not sure what to do next.

Can anyone please help?

STu.

 

[OrangeTJ]

When was the last time you changed the spark plugs? Mine did that when it needed new plugs. Under load it wouldn't rev past 6000 or so.

 

[Stuart Bicknell]

First thing I done. @OrangeTJ . However, 2 of the plug caps on the Port side engine were a little rusty!!! I'm not sure if that would cause any problems.!!!

 

[OrangeTJ]

Rust at the connection? That could definitely cause a problem.

 

[Speedling]

True! Where exactly was the rust?
Pictures are worth a million words

 

[Gym]

Rust on the plug caps could cause resistance to the spark plug reducing current to the plug resulting in unburned fuel in those cylinders. This would be the same result as a bad or incorrectly gapped plug.

Is there any visible water leaks, water vapor in your exhaust or water in your oil @Stuart Bicknell? A water leak COULD cause compression loss causing RPM loss under load.

 

[Stuart Bicknell]

Thanks Guys.

I will check all this out...but it will have to wait a week or so. The boat is out for the winter now but I do have to winterise it next week. I can take a picture of the plug caps.@speedling
From memory Port side engine back (stern) two plug caps were slightly corroded along the metallic strip that runs the length of the plastic cap. All other caps were perfect including all 4 caps on the starboard engine. I should replace these anyway! any idea where I can get them from?

As for water in the oil @Gym I have checked the oil on the Dip Stick and I don't see water.

Thanks again all.
Stu

 

[Cobra Jet Steering LLC]

That could mean several issues, my first suggestion is check the air filter for oil on it. Also you may have a stuck injector, if so the injector could dump excess fuel in your oil and cause it to be overfilled thus fouling the air filter element.

 

[txav8r]

If the problem is intermittent such as you describe from getting 8K rpms under load, and then last time you got 11K rpms, the rust on the caps could be causing you to be dropping a cylinder occasionally. Clean the corrosion out of the caps and use dielectric grease to make a more waterproof and corrosion free connection between the caps and plugs. The fact that it is an intermittent problem leads me to think this is electrical, and that too could be injector, but the caps are suspicious to me.

 

[Stuart Bicknell]

@txav8r It is not intermittent, Sorry for any confusion So I can only get 8000 rpm on one engine only and only in the water. Out of the water i can get full Rev Range on both engines.

 

[Cobra Jet Steering LLC]

Is the oil level high on that engine? I believe I would check the air filter element for oil, that is a very common issue with the mr1 engines. Remember out of the water doesn't mean a whole lot.

 

[Stuart Bicknell]

Thanks, I will check. I have only had the boat a few weeks, so not sure. I did check it had oil and it didn't need any more but can't remember if it was high. Can i check cold?

 

[txav8r]

Ok...confused...you said you now had 11K rpms, was that out of the water? Like Jeff said, without a load on the pump, it is meaningless.

 

[Cobra Jet Steering LLC]

Yes just be sure it is level those engines can not be overfilled or they ruin the air filter and run bad just like you are describing

 

[-klb-]

My recollection is bar these are resistor plugs, and that they can internally fail without evidence. The number one pice of advice on loss of RPM is change the plugs.

 

[txav8r]

@-klb- , he said he changed them...which lead me to thinking his caps were either not installed correctly, or they were corroded. Either way, oil overfill or spark plugs, even caps...pretty easy fix comparatively speaking. And I agree, they do fail without showing any external signs, much like a cap not being installed correctly!

 

[Cobra Jet Steering LLC]

I believe he said he did that first but it did not fix the problem

 

[Speedling]

In my talks with him he has changed plugs.
8000 rpm in water but has full rpm out of water. So with a load something isn't working right.

 

[Stuart Bicknell]

Hi Guys. Just to Re-Cap. 1st job i done, Changed plugs NGK CR9IEB. Thats when i noticed the Caps. 2 were rusty on the metallic strip along the shaft.

Need to replace them, anyone know where to buy?

thanks

stu

 

[Stuart Bicknell]

I could have that NGK number wrong !!! It was the Iridium version....