Mercrusier 350 MAG MPI - RPM issue under a load

[wbas1]

Just so you know what I did with the timing tool. I got the motor to TDC, then I rotated the motor to 10degrees BTC. Once I had the motor to 10 degrees BTC I used the timing tool to get it set dead on. I will get the other information tomorrow

 

[wbas1]

New motor and 150 psi all cylinders
New ECM from Merc
Firing order is correct and there is no misfiring, just low power
Timing is dead on correct using the timing tool per bulletin

For me, not the sharpest tool
Only thing left is there might not be enough advance in timing, or not enough fuel, or its not a vortec 350, or the wrong reluctor wheel was installed

Take a advance timing light and connect to number 1. Can be at the dock and rev motor up to see how much advance your getting

Look behind the heads on the block rear deck for a casting number. It will be a 6 to 8 digit number with no letters.

Update: 7/6. Timing at idle is 10 degrees. rev the engine and timing advances to 24 degrees. Also I have ITR4A 15 spark plugs. I did not have a gap tool but the gap looks big.

 

[alldodge]

Those are iridium plugs and don't try to adjust, the thin coating will crack
You have the correct plugs for the motor
Advance is good

You have done everything correct. It should be producing enough power if it was rebuilt correctly.

Don't think I asked this before, but look for the casting number on the block. It is below the head on the rear of the blocks deck. Will be a 8 to 10 digit number with no letters

 

[wbas1]

Those are iridium plugs and don't try to adjust, the thin coating will crack
You have the correct plugs for the motor
Advance is good

You have done everything correct. It should be producing enough power if it was rebuilt correctly.

Don't think I asked this before, but look for the casting number on the block. It is below the head on the rear of the blocks deck. Will be a 8 to 10 digit number with no letters

casting # is 10243880

 

[itsathepete]

casting # is 10243880

So it's an 880 block. very common 350 block. roller block. 2 or 4 bolt main. could have mechanical fuel pump or not. likely made in mexico

 

[alldodge]

casting # is 10243880

Good, at least its a 350

 

[wbas1]

Good, at least its a 350

Tomorrow I am going to try and spray some starter fluid in the Throttle Body when trying to get on a plan. That should at least tell me if it is starving for fuel.

 

[alldodge]

I would stay clear of starting fluid, maybe propane

If it wasn't so hard it would be nice to see it on a dyno. Its either not making enough HP or I'm back to weight, drive ratio, prop pitch and you've said those haven't changed

 

[wbas1]

Tomorrow I am going to try and spray some starter fluid in the Throttle Body when trying to get on a plan. That should at least tell me if it is starving for fuel.

I would stay clear of starting fluid, maybe propane

If it wasn't so hard it would be nice to see it on a dyno. Its either not making enough HP or I'm back to weight, drive ratio, prop pitch and you've said those haven't changed

I have heard that about propane but I have never used it. Nervous.

What is weird, when I had the old ECM installed and disconnected the MAP sensor, I was able to get the boat on a plan.

If the Knock sensor was preventing it, would that send an alarm?

 

[alldodge]

Starting fluid (Ether) has a lower flash point then propane. I don't even light using it to start a motor. I wouldn't use either for what you want to try, but would try propane before Ether

Would like to use something like Diacom software and get a recording of what's going on. Unplugging a sensor causes things to happen that would not be normal. If the ECM did pickup a knock it would retard the timing

 

[wbas1]

Starting fluid (Ether) has a lower flash point then propane. I don't even light using it to start a motor. I wouldn't use either for what you want to try, but would try propane before Ether

Would like to use something like Diacom software and get a recording of what's going on. Unplugging a sensor causes things to happen that would not be normal. If the ECM did pickup a knock it would retard the timing

I am actually trying to get someone with the right tools to work on this. The 1st guy I had could not figure it out. He was supposed to be top notch. Well that was wrong.

 

[wbas1]

Starting fluid (Ether) has a lower flash point then propane. I don't even light using it to start a motor. I wouldn't use either for what you want to try, but would try propane before Ether

Would like to use something like Diacom software and get a recording of what's going on. Unplugging a sensor causes things to happen that would not be normal. If the ECM did pickup a knock it would retard the timing

Ok - I was down at the boat tonight and I was able to get the boat on a plan. My mechanic sprayed ether into the throttle body while i was powering up and I was able to get the boat on a plan running at 4k.

We then decided to put the ECM into the default mode to confirm we did not have a collapsing fuel line. We pulled the plug on the MAP sensor and again I was able to get the boat on a plan running at 4k.

Now I just need to find out what is causing the fuel issue. Can the injectors be the wrong ones?

 

[wbas1]

Update: I had a mechanic come by over this weekend with a scan tool. Unfortunately it did not show any faults. I am trying to get a mechanic down to the boat with a laptop that can see a lot more detail in what is going on. The computer is not getting the message to give more fuel when it is needed.

 

[alldodge]

Is a puzzler, but even a scan tool in the hands of someone who knows how to use it should be able to determine what the issue is. Sounds like you wasted money with the first Mech. Hope the next is better.

 

[wbas1]

Is a puzzler, but even a scan tool in the hands of someone who knows how to use it should be able to determine what the issue is. Sounds like you wasted money with the first Mech. Hope the next is better.

I am still trying to get someone that has a laptop. Yes I put a lot of money in this motor and still no luck. I should have just bought a brand new crate motor and just put it in.

 

[alldodge]

Like member MUC (retired marine Master Tech) here has said many times. Getting and paying for a Tech that knows what their doing is expensive, but most times it will cost less to use them then someone who thinks they know what the issue is

 

[wbas1]

Still trying to get a good technician to look at my issue. never thought they would be so hard to find.

I do have a question though. Has anyone heard of clocking or timing the duo props on the Bravo 3. Both props are 3 blade.

 

[alldodge]

Yes,
Put first prop on and place one blade facing straight up
Put second prop on and place one blade facing straight down
It places all blades 33* apart

 

[Rick Stephens]

Yes,
Put first prop on and place one blade facing straight up
Put second prop on and place one blade facing straight down
It places all blades 33* apart

Curiosity impels me to ask - what difference can that make? In 15º of rotation the two props will be aligned with each other. Had to ask.

 

[alldodge]

Note quotes "It's said to get Max efficiency" due to the skage and housing, that said I don't see it. Use to do it, but got tired of it so I don't now and have not noticed any difference