175 ECU on my 150?

[mufugger]

Hey guys,

So, I have a 1998 Mariner Magnum 150 EFI. I'm looking for just a little more HP out of it. It's only an 18ft. fish/ski boat, so I don't want to get too crazy.

From what I understand, a lot of the 150's are exactly the same as 175's except for the ECU. So, in theory, I could replace the ECU from a 175 EFI and have a factory 175?

I know the 200's and 225's only have minor differences (intake, exhaust, etc.) but, that might be a project down the road someday.

If anyone can confirm I would appreciate it.

thanks!

[mufugger]

anyone? I just want to make sure before I start looking for a 175 ECU. ;)

[silverbullet02]

I wouldn't. The only thing the computer really controls is fuel, so all it will do is make you richer and probably slow you down.

[dynobo]

The 150 doesn't have the same porting as the 175/200 so adding the 175 ecu could very possibly make you slower as already mentioned. I do know adding a 200 ecu to a 175 will definitely wake it up. Learned this by mistake trying to troubleshoot a bad 175ecu. just my .02

[mufugger]

thanks for the replies guys. I thought the 150's and 175's had the same porting, and the 200/225's were the same.

This is one of the threads that led me to think this (look at the last reply):

http://forums.screamandfly.com/forums/showthread.php?t=106640&highlight=175+ECU+150

as well as this thread:

http://forums.screamandfly.com/forums/showthread.php?t=196046&highlight=175+ECU+150

[dynobo]

I have several 150's just no 150 2.5 efi so I am not sure on the porting but, I was thinking the port timing was less. I know the 200/175 efi are the same as I have checked many of them. It won't cost you anything to borrow a ecu off a 175 and try it. The post about the 7mph gain is probably stretchin it some as a 175 probably won't pick up 2-3 mph on the avg bassboat vs. a 150.

[dez nuts]

anyone? I just want to make sure before I start looking for a 175 ECU. ;)Yes if you have a 2.5 150 efi it will run better with a 175ecu i have done it and it was good for about 300rpm with the same prop. Dave PM me will let you know what i have found with doing this. Dave:thumbsup:

[Simon]

I can upgrade your ECU.

[TEXAS20225]

Will a 175 carry a 200 ecu with out making it too fat I know my 200 would not run my 225 pmax ecu way too fat

[dynobo]

Will a 175 carry a 200 ecu with out making it too fat I know my 200 would not run my 225 pmax ecu way too fat

I don't know the rpm picked up but we gained about 3.5 mph on a 19' RANGER. I took the ecu off my 96' Mariner 200 MAG and put it on a 97' Mercury 175efi and it almost became a different motor.

[dynobo]

Will a 175 carry a 200 ecu with out making it too fat I know my 200 would not run my 225 pmax ecu way too fat

Also, only real difference I have seen between the 200 and 175 efi's is the ecu and MOST (I do have a couple 200's that do) 200's don't have the idle reliefs. I have 2 (93)' model 200's that do have the reliefs but not sure why.

[dez nuts]

Will a 175 carry a 200 ecu with out making it too fat I know my 200 would not run my 225 pmax ecu way too fatIt will give it more topend but it will run fat thoughout the hole rpm range the 200 is alittle different porting than the 150and175's but the 200ecu will run faster on the 175and 150 but will use quite abit more fuel and run rich but will run good. The 200 doesn;t seam to like the fuel durve of the 225 and thats mostly due to the 225 being a 7petal front thus give alot more air than the 200 can diliver meaning it;s pig rich with less air flow.Dave

[dez nuts]

Also, only real difference I have seen between the 200 and 175 efi's is the ecu and MOST (I do have a couple 200's that do) 200's don't have the idle reliefs. I have 2 (93)' model 200's that do have the reliefs but not sure why.Those would be the first 200;s that i have seen with compression reliefs i would bet they are 175 blocks, Look at the letter on the throttle side of them and see what letter it is CC will be 175 and FF will be 200 also there is a big difference between the ports in the 175 and the 200, Let us know what letter is on the side of your motors Thanks Dave:thumbsup:

[wrechin2]

It really depend on years....Some 150's, 175's and 200's have the same porting. Some 150's and 175's have the same porting. If you look at your sleeve applications, you will see that some of 150's, 175's, and 200's use a LA079. Some of the 150's and 175's use LA151. Sleeves come with the ports already cut in. The LA079 sleeves ports are 1.610 on the exhaust and 2.215/2.175 on the transfers which is considered "Standard 2.5 200" porting. I have put several of the LA079 sleeves in. A 98 150 should have exhaust porting of 1.740 and have the idle relief. I recently cut one to 200 specs and put a 200 ECU on it. It runs great. Very strong even with the reliefs. I don't remember what the transfers were, but they were like .050 lower best I can remember. Didn't write down as I know of no one wanting to port to a 150 :rolleyes: These are Just my experiences......

[mufugger]

thanks for the replies and info.

so, it would be safe to assume that a 175 ECU will net me a few more miles an hour at least?

[wrechin2]

If the porting is the same as the one I cut, then It will actually flood the engine and slow you down. If you have access to it, would be one of those things you will simply have to try, JMO...

[dynobo]

Those would be the first 200;s that i have seen with compression reliefs i would bet they are 175 blocks, Look at the letter on the throttle side of them and see what letter it is CC will be 175 and FF will be 200 also there is a big difference between the ports in the 175 and the 200, Let us know what letter is on the side of your motors Thanks Dave:thumbsup:

Dez nuts, I can't really find absolutes with these Mercs. I am just saying what I have seen. I still have dozens of these motors from different years and the specs for them are all over the board. I have seen the BB,UU,HH,CC,EE,FF codes on blocks as well. Wrechin and I have been comparing notes for about 3 or so yrs on ports, block numbers, castings etc and sometimes there just ain't no rhyme or reason to these things.
On the 200/175 ports even on the chrome bore the 175 and 200 were pretty much identical. I have measured numerous of them and they are very similar. Sometimes 2 200's from the same year may be different. I have (2) 2.4 1988 chrome bore 200's virgin blocks sitting on my bench at the shop and one has 1.602 ex. height and the other 1.618. Go figure. I never claim what is or what ain't, just what I've seen. Likewise with the ECU's I have never tried the 150-175 swap but have now done several 175- 200 swaps and have never had anyone wanting to put there 175 ecu back on. Again just my .02. :cheers:

[wrechin2]

We have came across some wild stuff..... I had a 2.0L that had .005 staggered porting FROM THE FACTORY. It was a factory replacement for a 88 XR2 that was date stamped 94 and was a vertical engine. Customer had it put on just after he bought it. No one had been in it except me. I found the porting was 1.640,1.635,1.630,1.625,1.620, and 1.615. I stood back and scratched my head for a few minutes and then cut them all to 1.595 and called it a day. Engine really woke up. I have a XR2 that has 1.665 exhaust porting and the normal is 1.640~1.650. There is no ryme or reason for what mercury does.........Just my experiences.......

[mufugger]

gotcha. so, ill find one to give a try this spring and ill post back in this thread.

thanks guys!

[wrechin2]

:thumbsup: I have done a alot of things other people say not to do just so I can know for myself if it works or doesn't. I have had many thing work that other say won't. I personally think it will be rich to the point it will loose RPM, but you may put it on and find it runs a lot better. What I find is the APPLICATION on which it is tried. What may not work for a "RACE" engine may have very good results on a "FISHING" engine and vice versa.

Prime example.....I done what Texas talked about with a 225 ECU on a 200 5 pedal engine. Mine was a pretty heavily modified 175 and did run rich, but not pig rich like his did due to the mods. Modified engines need more fuel, so I was using some of the addition fuel, but not all of it but still needed more fuel than my 200 ECU could deliver. SO I have 4 choices...Modify it even more and keep the 5 pedal and hope it can use more of the fuel, buy a PCU, Carb it, or change the front to 7 pedal and just make a 225 out of my 175 and use the 225 ECU....

I have bought the stuff to make it a 7 pedal :cheers:

Hope this helps....