350 mag mpi surging under load

[silver_power]

Update: The problem did not solved. The fuel pressure is 43psi (perfect), but the surge still exists. I left the boat to the mechanic to solve it. I am totally tired. Things are changed are: new plugs, new rotor and cap, new plug wires, new fuel water separator, new mapt sensor, new tps sensor, checked and cleaned fuel injectors, new fuel pressure regulator, checked compression leak down test (all cylinders 165-170 psi). I do not know what else to check.......
My boat does not have anrisyphon valve as the fuel pump is below tank fuel pick up. The test today was made with a remote fuel tank......

 

[ghunttwo]

I solved my problem, I ordered a new shift lever spring and a shift assist spring assembly. I removed the shift plate and took the whole thing to the bench. dissembled it , oiled up all the pivot bolts , replaced the lever spring which had been bent, I think on purpose , adjusted the switches. I have the service records from the X owner and he was taking it in for the same complaints. Put it all back together with a new shift assist assembly.
​It now shifts and runs up to 5100 with no hesitation or shutting down.. I was getting quite angry looking at my unusable Toy.

I do hope this might help in some way Silver Power. The process took only 1 hour and cost just 46.00.
Hop you get yours going for next season.
Ghunt

Some times we tend to over think things and over look the simplest.
​

 

[silver_power]

I am happy that you finally solved your problem. Unfortunately this does not happen to my boat. I have not made something further than final test with bad results.I will change these days the spark plug wires and retest at the sea but I will check if the shift plate operates normally just to isolate a possible problem like yours. Thank you for the tip.

 

[silver_power]

Well, after some time i decided to work again on my boat's issue, since the new spark plug wires arrived.
I had some time and i checked the distributor's position. So i removed the spark plugs to rotate the engine till the #1 TDC (compression). I checked the rotor's position and it was off the #8 mark (inside the distributor housing) about 10 degrees retarded at the distributor (meaning 20degrees at the crancshaft). I think this is a lot. So i reinstalled the distributor such way so the rotor face exactly the mark #8. I changed the wires as well....I do not know if this is the problem of the surging under load....i will find out next time i will test it in to the sea.

 

[alldodge]

Hope this does it for ya

 

[tpenfield]

I'm not following the #1 TDC vs the #8 mark on the distributor . . . but maybe I missed something along the way.

Is the #8 mark related to the #1 cylinder?

 

[silver_power]

Absolutely...when the balancer mark is aligned to the block mark at #1 cmpression (firing) point, the distributor rotor must be exactly to mark #8 of the distributor housing.. This happens at ecm 555.

 

[silver_power]

Problem solved!! After the distributor proper clocking , changed the spark plug wires with new, I finally tested the boat today and the results was perfect. Thank you all for your help. I wish good summer for all.

 

[QBhoy]

Having changed the diz and rotor on mine once and cleaned it more...I can’t think how it could be on the wrong way (earlier reference to #1 & #8) am I missing something ?

 

[silver_power]

What do you mean....I can not understand.

 

[silver_power]

I would like to ask something about the correct procedure of distributor phasing/clocking. My engine has SN: 1A348183, and I am little confused. I should position the distributor such way that while the harmonic balancer is at 0 degrees (TDC) the rotor is exactly at mark 8 index, or like the way you described at posts #48-50 with the led light and the decal put ed at harmonic balancer?

 

[alldodge]

The post in 48-50 was a quality control and poor design fix issue as I see it. The bulletin is for "cylinder misfire limit exceeded" and can be caused by many things, even a new distributor that was made within tolerances but when matted with a motor at the other end of tolerances, there would be an issue. GD&T was not used but this is a whole other topic

So if you install the distributor as in the bulletin you will be dead on the mark. The dizzy is installed with #1 at TDC, then rotated until the led lights showing the actual cam sensor position.

If the motor is not having a misfire condition, or if this is just to install the dizzy where it should be, place on TDC, install dizzy where rotor points to the notch (mark 8 on edge)

 

[silver_power]

Let say this procedure is a fine tuning of the dizzy position? My motor has 450hours , is it possible that the procedure with the light to give me a little to tiny deviation of the dizzy direction because of the tollerance of the chain, gears etc, comparing now i installed the dizzy exactly to mark 8? I am asking this just because this construction with the led and the resistor described at the bulletin is very easy to me.

 

[alldodge]

Don't know if it will help, but there is no way it can hurt.

 

[QBhoy]

The mpi distributor can only go on one way. The rotor can only go on the way the old one came off...
I still don’t see how the replacement can go wrong.

 

[alldodge]

The mpi distributor can only go on one way. The rotor can only go on the way the old one came off...
I still don’t see how the replacement can go wrong.

Don't want to get off track, but the distributor can go in like any other distributor. It can be installed dead on and anywhere in between up to 360 degrees out. The issue with the HVS is there is no timing light to adjust, it can only be adjusted by the placement of the distributor in reference to the rotor, crank and cam

 

[QBhoy]

Don't want to get off track, but the distributor can go in like any other distributor. It can be installed dead on and anywhere in between up to 360 degrees out. The issue with the HVS is there is no timing light to adjust, it can only be adjusted by the placement of the distributor in reference to the rotor, crank and cam

Hi AD...unless I’m miss understanding...remember the mpi diz cap isn’t round like the others. It’s pretty cool proof. It’s shaped to fit the base and the screws and shape mean it can only go the one way. Not like the old carb engines at all.

 

[QBhoy]

It’s like this.

 

[alldodge]

Hi AD...unless I’m miss understanding...remember the mpi diz cap isn’t round like the others. It’s pretty cool proof. It’s shaped to fit the base and the screws and shape mean it can only go the one way. Not like the old carb engines at all.

Back Howdy
No, while the cap outer appearance is not round, the rotor does turn in a circular fashion and the shaft of the dizzy can go it from 0 to 360



So long as it rotates , the base can be rotated

 

[QBhoy]

Back Howdy
No, while the cap outer appearance is not round, the rotor does turn in a circular fashion and the shaft of the dizzy can go it from 0 to 360



So long as it rotates , the base can be rotated

Haha...yeah understood...but the HT leads on either side would surely give the game away. If the engine hasn’t moved since removal, the rotor can only go where it came off.
Even the hold down screws mean you can’t go far wrong. The cap has cyl numbers on each ht port too. You’d need to break it or god knows to get it wrong surely.