Mercruiser Engine Problem
 

I have a 1999 Formula 312 fast tech with 2 454 mercruiser engines. One engine is giving me problems and I would like to know if someone has encountered this problem before. One engine under load goes into a cutting on and off sequence. I have changed rotor and cap module plugs and checked alot of other things. Nothing seems to be bad and the items that I changed did not help. Now again this only happens under load past 2000rpm. Can someone assist me on what to do next? Thanks. :mad:

Re: Mercruiser Engine Problem
 

I had that happen on one of my 525sc's. It ended up being the coil. Try changing the coils around and see if the other motor skips.

Re: Mercruiser Engine Problem
 

Do you have the ability to scan the ECU for codes? Did you chnage the fuel filter?

Re: Mercruiser Engine Problem
 

The above is all correct Im guessing that they are mpi motors if the above checks out ok also check the iac ( idle air control if that is bad it will seem to be doing what you are saying ) # one to check as mentioned above is the fuel filter and fuel press...and then if it has a vst (vapor sep ) check the float and needle and seat ...also you didnt mention if the cond of the plugs and if running rich lean ect....

Re: Mercruiser Engine Problem
 

Anything off of idle, the IAC has no effect even if it's defective.

Re: Mercruiser Engine Problem
 

oh ok sorry :rolleyes: guess im wrong that if its stuck open its not allowing extra air in, im sorry guess im wrong and that wont effect anyting out of idle or that if its bad the motor wont go into limp home/ guiardian mode sorry im wrong



oh ps call merc tech and tell them also because they dont relize that

Re: Mercruiser Engine Problem
 

i just had the same problem so i changed the water seperator & then the fuel pump.
it was the fuel pump

Re: Mercruiser Engine Problem
 

sorry didnt mean to get pissy but just because something when working properly only effects idle doesnt mean that when its not working properly it doesnt effect other things ie the iac. been doing this a longggg time and ill be the first to admit that im not always right but ..........


anyone who says they are always right I wouldnt trust anyway !!!

Re: Mercruiser Engine Problem
 

this is from the merc tech manual


I know I know the iac does nothing out of idle

Re: Mercruiser Engine Problem
 

I had the same systems on my 95 454 merc. It turned out to be the coil.I didn't find it till after I changed everything but the stringers the engine was mounted to.I just happen to be working on it while it was getting dark and had the engine running.I noticed and heard a zapping sound and saw the sparks coming out of the coil tower and shooting to the wiring system.It was a pain the the transom because it would run good for about 10 minutes till the coil got hot and then start breaking up under load and then would die.Hope this helps.

Anthony

Re: Mercruiser Engine Problem
 

easy way to tell if coil... when they go bad ..usually it because theres a short it gets hot expands shorts out totally dies till it cools then starts back up. when it stalls touch coil if very hot theres you problem.. thats the back yard way the other way is to use a dvm ( digital volt meter) and check the ohms resistance.

Re: Mercruiser Engine Problem
 

Seen a lose wire on the circuit breaker do that.Also a bad key switch.

Re: Mercruiser Engine Problem
 

A engine grounding problem can easily be the culprit. Don't spend money until you've made sure it is not a ground problem.

Re: Mercruiser Engine Problem
 

That symptom (surging at high RPM) can be a caused by several things, but I don't think the IAC motor is one of them. A few suggestions:

Check battery and engine power and ground connections as suggested above.

Check Knock Sensor and Ignition Control circuits (wires) and make sure that they are not touching any spark plug wires.

Check for trouble codes.

Check fuel pressure under load.


Dave

Re: Mercruiser Engine Problem
 

I agree with dave but surging isnt what he said, cutting out is granted its a fine line but with out running the boat have to go with what is said. and im not saying that thats what it is just saying check it. could be it along with fuel press coil ect. can sit here and give 200 reasons but have to go step by step till you find the culprit. thats why theres flow charts and short cuts but if not in front of you you can only say to check in order of elinination

and yes my spelling sucks

Re: Mercruiser Engine Problem
 

Look hotshot, first of all, I never said I'm always right. Second, you never said you were in a limp-home mode, so I assumed you weren't or you would have (should have) mentioned it.
Third, I'm trying to help you with my experience. If you think disrespecting me when I'm trying to help you is cool then go phuck yourself and everybody that looks like you.
Ed Cozzi

Re: Mercruiser Engine Problem
 

ok here we go first its not my boat read the post....

second, I dont survey boats I fix them....

third..... i THINK first before I tell someone something....

fourth.... after 25 yrs I think ive proboly been doing this longer then you....



if I wanted to be mean and dis you I would of told you to eat s*it and die

I have certs from merc, omc and volvo and you...???????



oh and no im not a hot shot just 42 yrs old been doing hp boats for a long time and no im not always right just not wrong often and dont like being put down when im not wrong if i am then go for it.. if your not 100% sure when you say something then say I think the iac only controls idle. dont mke it sound like you know 100% that im wrong when im not!!!!!!!!

I take alot of pride in my work and try not to be wrong

I dont survey boats

you do

do you want me to say more

Re: Mercruiser Engine Problem
 

I just realized that "Mr. trying to be clever," GoodT, didn't start the thread.

Well, here's my take on your suggestion about the IAC with the symptoms mentioned: YOU MIGHT AS WELL HAVE SUGGESTED HE TEST THE WINDSHIELD WIPER SWITCH!

It's punks like you that keep a lot of guys from posting here. Sarcasm has yet to fix any boat I've ever worked on.

Re: Mercruiser Engine Problem
 

Look, Punk, I'm 57 years old and have probably forgot more than you'll EVER know.
You had a lot of nerve disrespecting me. I am WAY more than a surveyor and always have been. I was already over the wet-behind-the-ears mode when I was 42. Hopefully this might happen for you.

Re: Mercruiser Engine Problem
 

Hello to all that took the time to answer me. I did do the fuel filter. I did check the fuel pressure but not under load just on the lift out of the water at idle. I did not change the coil yet. I will try and change the coil and then try to change fuel pump and see where that takes me. Please if you have any other suggestions please feel free in contacting me. THANKS AGAIN TO ALL.

Re: Mercruiser Engine Problem
 

You will find your problem as long as you disregard whatever suggestions the punks make.
Ed Cozzi, not hiding behind a screen name, just trying to help a fellow OSO guy enjoy his boat.

Re: Mercruiser Engine Problem
 

Does this engine have the electric transfer pump mounted on the engine pull the top cover and clean the screen in it and re assemble. test the fuel pressure under load check the spark at the plug with a st125 spark tester try it under load also. :drink:

Re: Mercruiser Engine Problem
 

look im not going to get in a sh*ting match with you I guess you are just a better man then me long and short you are wrong... I may or may not be right im glad that you are older then me and means that might be able to have a good debate with you but long and short iac does make diff other then idle... and thats cool and I havnt gotten nasty but you have so.......
and no im not a "punk" and as a marine surveyer you should maybe learn about fuel injection systems before you tell people what there boats are worth. if you dont know then dont say any thing remember its always better to say nothing then to prove that you know nothing( thats the nice way to say it) and if im wrong then ill be more then happy to so the manual again....just be a man and say you where wrong....

I was willing to end it nice till you called me a punk.......

I dont go there..........



you hammer on boats I fix them !

Re: Mercruiser Engine Problem
 

Come on guys. We are on here to help me not to fight with one another. So please just keep the good suggestions coming. Thank You.

Re: Mercruiser Engine Problem
 

thanks stud you are right

Re: Mercruiser Engine Problem
 

I'd really like to get in a battle of wits with you, but I don't go after the unarmed.

I stand by these statements:
1. You are a punk to think that an IAC would cause the symptoms listed.
2. You also were a punk to disrespect me as a person you don't even know.
3. Your people skills are as poor as your English grammar and spelling.
4. You assumed I was posting as a Know-it all and you could have corrected me without attempting to make me look foolish. You chose to build yourself up my tearing me down. Says a lot about your character.
5, You are an embarrassment to this site.

Re: Mercruiser Engine Problem
 

well I think you should re read when you arenot drinking /high because I didnt


then I think that you should look at the attachment realllll close beacuse it says it can

then till you called me a "punk" I never directed anything at you

as for being foolish I never said that you did

oh and sorry I didnt hit spell check when I went to school didnt have it and as* its not the spelling its the thought

Re: Mercruiser Engine Problem
 

Mmmm .. kinda nasty here, think I'll leave this thread alone and take up a cool one. :drink:

Re: Mercruiser Engine Problem
 

you know what ed I think im going to leave andl et you fight with yourself
you seem good at that

Re: Mercruiser Engine Problem
 

Go back and read post number 6 and tell if if all that crap was necessary. All you had to do was tell me like a gentleman instead of an azzhole and you would have gained my respect instead of the way I feel about you now.
We could have avoided all this if you had some people skills.

You don't even know who I am. For the record: In my teens, many years ago, I was a proof-reader and typesetter for a printing firm. I don't need SpelChek. I don't drink nor do I get high. (Anymore).

I still think you are way off even mentioning the IAC with the symptoms given. Even if it was stuck open, the computer would adjust so the mixture wasn't too lean. You were reaching with that one.

Re: Mercruiser Engine Problem
 

Yes punk, go hide. You've been out-classed here.

Re: Mercruiser Engine Problem
 

you know what im man enough to say I was wrong you are right I dont know what I talk about.. and the iac can't do anything after idle and ill call merc tomorrow and tell them that they are wrong and im a punk that knows nothing about fuel injection and to please take my certs beacuse I know nothing and then ill call all my customers for the last two years that I built there motors and drives and tell them I know nothing and that they are sh*t out of luck ......because there fountains, actives and sonics wont
live and im a punk... and know nothing cool

Re: Mercruiser Engine Problem
 

ED try to have a nice day! :cool:

Re: Mercruiser Engine Problem
 

you know if nothing else you are fun ..... .......... thanks

Re: Mercruiser Engine Problem
 

More proof I'm right about your character.

I hope you work in the back-room where you never have to come face-to-face with the customers.

Re: Mercruiser Engine Problem
 

You're welcome. Now I'm going to bed and dream about engines cutting out at 2,000 RPM and trouble codes and bad fuel and shorted out ignition systems and it's all studstud's fault!

Re: Mercruiser Engine Problem
 

This is a longshot, maybe even way out there, <US1 ducking down low> but a friend had a very similar condition this summer with one of his 454 mpi's. that went on for a few days. Ran fine, then for no reason while running it would cut in and out. Back to idle, all is fine. Back into the throttle, start cutting out again. Finally dead. Turned out the main wire harness plug came loose at the rear of the motor. It was still connected, but not making contact. The cutting in and out must have been while the plug was working it's way out.

Re: Mercruiser Engine Problem
 

Did anybody mention the IAC motor yet???? :eek: Sorry couldn't resist... :D :D :D

The coils are seemingly a common failure just swich them on your motors see if the problem moves, as mentioned above check wiring, power grounds. I actually had a similar problem and it ended up being a bad connection for the main power supply under the dash to my fuse panel, good luck...

Re: Mercruiser Engine Problem
 

Just a shot in the dark here, but my father had this happen years ago on one of his 454 mag/efi's. It turned out to be bad batch of gas and a plugged fuel filter. Hope it might be something that simple.

Re: Mercruiser Engine Problem
 

I've seen a bad ground connection, wiring harness, connction, etc be the culprit more then once, after the owner has thrown $$$ away replacing many parts with symptons you've described.

Disclaimer: I'm not a mechanic nor surveyor but rather just a dumb azz who's " been there done that " with issues such as yours.. :evilb: