Merc 150 4S

[108]

turbo.

[LakeFever]

Made a mistake in my math above 3L is 183 cubic inches which puts the 1.6hp per cid @ 293

[PanRonnie]

We had this discussion in general discussion
https://www.screamandfly.com/showthr...s-engine/page2

where we put up some more info into it
https://www.screamandfly.com/showthr...s-engine/page3

You can go nuts with mods but how much are you spending?
first thing to me would be valve spring upgrades then custom cam job where you could have a look at LS2 cam profiles as the 150 4s looks a lot like a halve LS2
Maybe loose the balance system?

[LakeFever]

ahhhh I see. Well that makes sense seeing as Merc has been attached at the hip with Chevy so so long. This sure makes it easy to spec a cam. Piece of cake in fact. Just regrind the stock merc core to spec. I’d take one of two approaches here.

1. Race motor; use extreme lobe rpm limit in the mid-high 7000’s and dual springs with a solid head port etc. this will be easy to hit the 1.6hp per cid number but this will not last long in a marine motor. The valve springs will need regular changes and the propping and lower ratios will need to be adjusted accordingly

2. endurance lobe cam in the goof proof area of 224 on a 112 or maybe even a 110 something like that I’d look at events that did not reduce torque down low but opened it up above 4500 and limit around 65-7k this would be decently reliable and produce approx 25% more hp which would be cheap and easy. Cam, beehive springs, tune, ought to do it. So a 150hp would turn into a 188hp which ain’t too bad for how easy this would be. The only serious cost issue going in would be the Holley system. Once on the Holley your dreams open right up. Boost or whatever all easy to add at this stage. Add a 150shot maybe? Plenty of things to do.


Maybe I’ll look into one of these for my vandal down the road. Maybe.

[25two.stroke]

Can someone explain to me how sequential fuel injection can work on a motor like the 150 3.0L where there is no cam sensor? How does the ecm know if it is a tdc on the power stroke or the exhaust stroke?

[Tcatrett]

Can someone explain to me how sequential fuel injection can work on a motor like the 150 3.0L where there is no cam sensor? How does the ecm know if it is a tdc on the power stroke or the exhaust stroke?

Probably best to leave it batch fire and waste spark? I'm looking at a Maxx ECU to test on mine.

[25two.stroke]

Probably best to leave it batch fire and waste spark? I'm looking at a Maxx ECU to test on mine.

They are waste spark, but they also have individual cylinder spark advance. Also they are sequential fuel injection. I am talking about the stock engine management system from Mercury. I cannot wrap my mind around how Mercury achieved this without a cam position sensor.

[PanRonnie]

They are waste spark, but they also have individual cylinder spark advance. Also they are sequential fuel injection. I am talking about the stock engine management system from Mercury. I cannot wrap my mind around how Mercury achieved this without a cam position sensor.

Injection in two stroke mode
In other words every 360 dgr crank rotations
You just have double injector opening and closing times not a problem if you don,t rev high
6000rpm is a 10 Milisecond rotation
They can't have individual spark advance as it is a duel output coil also something you might want to change

[25two.stroke]

Injection in two stroke mode
In other words every 360 dgr crank rotations
You just have double injector opening and closing times not a problem if you don,t rev high
6000rpm is a 10 Milisecond rotation
They can't have individual spark advance as it is a duel output coil also something you might want to change

It does have individual cylinder spark advance. You can watch it work on G3. I don't understand it. But 1&4 and 2&3 will be trimmed differently. The ecm knows when its firing the coil on cyl 1 TDC power (cyl 4 TDC exhaust stroke) versus 1 TDC exhaust and 4 TDC power and can trim accordingly. Even though it is the same coil. Which leads to my initial dilemma of how does the ECM know!

There are 4 injector drivers in the ECM. It would be pretty stupid to then fire them in batch injection. Also, this is just a guess, I do not believe the fuel efficiency of the 150 4s 3.0L would be achievable with batch injection...it would be about half as efficient as the previous generation of DFI motors. Moreover, the last generation of 90/115 motors (1.9L) had cam position sensors in them and individual cylinder pencil coils. When the CPS failed in these motors they would default to batch injection and continue to run. Then run horribly in batch injection. You can tell they are rich and inefficient. It seems that mercury only uses cam position sensors in their engines with independent coils for each cylinder.

[PanRonnie]

It does have individual cylinder spark advance. You can watch it work on G3. I don't understand it. But 1&4 and 2&3 will be trimmed differently. The ecm knows when its firing the coil on cyl 1 TDC power (cyl 4 TDC exhaust stroke) versus 1 TDC exhaust and 4 TDC power and can trim accordingly. Even though it is the same coil. Which leads to my initial dilemma of how does the ECM know!

There are 4 injector drivers in the ECM. It would be pretty stupid to then fire them in batch injection. Also, this is just a guess, I do not believe the fuel efficiency of the 150 4s 3.0L would be achievable with batch injection...it would be about half as efficient as the previous generation of DFI motors. Moreover, the last generation of 90/115 motors (1.9L) had cam position sensors in them and individual cylinder pencil coils. When the CPS failed in these motors they would default to batch injection and continue to run. Then run horribly in batch injection. You can tell they are rich and inefficient. It seems that mercury only uses cam position sensors in their engines with independent coils for each cylinder.

1 and 4 in waste spark would fire at the same time in the first cycle of 720 dgr same as 2 and 3 but only 2 would actually do work
So all cylinders fire every 360 dgr
Same with injectors firing every 360 crank dgr but sequentially this can be caculated from the missing tooth
Think i have a yamaha fourstorke manual which explains this same strategy
I saw a webinar from a gm proffesor explaining you would want to inject on a hot intake valve to maximize evaporation to improve the incylinder burn
Offcourse at lower rpm this give slightly less economy and poorer emmisions as some fuel will now go into the exhaust during valve overlap
With full sequential you could detard injection to start after the exhaust valve closes but this is for emmisions only
I don't think the ecm knows which cycle a cylinder pair is in like you mention with 1 and 4 or 2 and 3 for that something must give a 720dgr pulse like a cam sensor which is not installed
Megasquirt has a provision to sample the manifold pressure on a v twin to check the cycle but i doubt very much mercury botherd with that on this four cylinder