Mercrusier 350 MAG MPI - RPM issue under a load

[wbas1]

send the injectors out to be cleaned and flow tested

water does not automatically mean hydrolock

Then how would water get in there? Fuel is clean because I tested it.

 

[Scott Danforth]

Then how would water get in there? Fuel is clean because I tested it.

could be a head gasket leak to the cooling water jacket that only leaks under load, could be the start of a manifold leak, could be the start of a head crack leak.

pressure test the cooling water jacket to be sure

 

[wbas1]

send the injectors out to be cleaned and flow tested

water does not automatically mean hydrolock

Then how would water get in there? Fuel is clean because I tested it

could be a head gasket leak to the cooling water jacket that only leaks under load, could be the start of a manifold leak, could be the start of a head crack leak.

pressure test the cooling water jacket to be sure

This is a reman long block this year. I only put on the Intake manifold and the other miscellaneous items. I have been having this issue since May. i would think something else would pop up since then. I have had leak down tests done, compression tests & valve adjustments.

 

[alldodge]

You have very little time on the plugs so I'm not ready to say somethings wrong. Your not able to get up on plane so there motor is lugging and lots of fuel being burned. Pulling the MAP sensor has the injectors dump more fuel. To much fuel washes plugs and can also wash oil from the cylinder walls and cause scoring

 

[Rick Stephens]

The difference in the plugs from hole to hole is startling. I can see how you are frustrated. IMHO, if you had water in those white insulator holes, the entire insulator would be white, not just 2/3rds of it.

 

[wbas1]

The difference in the plugs from hole to hole is startling. I can see how you are frustrated. IMHO, if you had water in those white insulator holes, the entire insulator would be white, not just 2/3rds of it.

I feel like I have been hit by a bus several times and it keeps backing up over me. LOL. I am trying to get another mechanic down to put the software to it so I can get all the readouts and see what is going on. At least send it to you guys so you can tell me.

 

[Rick Stephens]

I feel like I have been hit by a bus several times and it keeps backing up over me. LOL. I am trying to get another mechanic down to put the software to it so I can get all the readouts and see what is going on. At least send it to you guys so you can tell me.

I'd be losing it a bit. I never take anything to a shop unless I totally fail - like I have an oil seal on a rear wheel of my Chev 1 ton that I have replaced twice and still leaks. I'm contemplating seeing if someone else can see something I'm missing. Generally, between asking for advice from here, or reading until the cows come home, I figure it out. This one is nuts. My sneaking suspicion is the ECM is off the rails here. Looking at the plugs makes me wonder if there is an issue with ignition the way some of them are blacker than than the inside of an old wood stove. Which could just be from the typical crappy Chevy big block valve seals. IDK. Hang in there. Something will pop up and resolve this yet.

 

[alldodge]

Not to get off track, but Rick
Wheel seal, maybe speedy sleeve to let the seal fit tighter

 

[Rick Stephens]

Not to get off track, but Rick
Wheel seal, maybe speedy sleeve to let the seal fit tighter

LOL. Good thinking. But those are the internal 2 piece truck seals. Second time I replaced the seal used every trick to make sure it went in straight with even pressure. Still seeps, darn it.

 

[wbas1]

Ok now back to my issue. Lol. Anyone feel I should pull the injectors and have them tested or possibly by new ones. The 1st mechanic said he cleaned them but not positive.

 

[alldodge]

I'm still thinking drive ratio, but if you want to have them clean and flowed, PM me and I'll give you a name and number

 

[wbas1]

I'm still thinking drive ratio, but if you want to have them clean and flowed, PM me and I'll give you a name and number

I guess I do not under stand the drive ratio question. I would think, even if the drive ratio was higher then 2:1 it would eventually get to rpm’s

 

[alldodge]

If prop pitch is to high for the motor to turn it won't.

If you understand a manual transmission, think about trying to climb a steep winding hill starting in high (4th gear in 4 speed trans). It will climb easy in 2nd, but will not be able to in 4th

 

[alldodge]

What pitch props do you have?
and think they are 4 blade but can't remember what you said

 

[wbas1]

What pitch props do you have?
and think they are 4 blade but can't remember what you said

4 blade 18 pitch. I can at least slowly get the boat on a plan. Just only to 3800 rpm’s

 

[alldodge]

If memory serves yours is a 4B in front and 3B in rear (4x3 Merc XR series). If so your slightly larger then a 18-3x3 standard prop. If its a 4x4 then you could go to 18-3x3

In short you have the smallest pitch props made for the B3 so there is no where to go

If its not the ratio, I'm out of ideas.
If the injectors are flowing to much fuel now, why now and not doing the same with the previous motor?

 

[Kianoushaa]

Hello friends, we also have this problem that the engine revs up to 4,500, 5,000 when stationary, but it does not increase to 2,000 while moving, and the oil pressure is not constant and it plays constantly.

 

[Kianoushaa]

More pic

 

[alldodge]

Kianoushaa please start your own thread, we will help

 

[wbas1]

Update: I had a mechanic come down and run some tests. He hooked up the laptop and ran a few tests. No faults, no errors nothing. He did pull the spark plugs and saw that 1 & 8 are running reach. We also noticed that there might be leaky injectors. We turned the key on, pressure to 40psi then dropped right away. We did that 3 times with the 1st 2 times the pressure dropped then the 3rd time it stayed at 40psi. He was suggesting getting the injectors cleaned and flow balanced. Then put the 2 injectors we think are the issue into a different location and see if the issue is still present. If so then he would look at possibly valve issues. I thought that would be present in the leak down test? Not sure if I want to have the Chinese injectors cleaned and tested again or just go buy the Bosch injectors.