5.0 MPI hard to start after impeller and tstat changed

[2001SportFailboat]

history..
I have a 2002 5.0 MPI with a 2beep mystery alarm that doesnt show up on smartcraft, but gives my northstar a red temp icon.. the boat would start within a few seconds of turning the key and the alarm would trigger during that time. I noticed that the serp belt was slipping so i replaced that along with the thermostat, since i noticed my temp was running between 110 at idle and 130 around 3000 rpms.. while the belt was off, i noticed the sea pump was tough to turn, so i replaced the impeller.
before replacing the impeller she started up like normal, and the temp issue seems to be within specs 160now. but now with the new impeller, it doesn't want to start with out melting the battery wires..
after some frustrating time of cranking the motor, changing throttle position, it will start, and the temp alarm will now go away until i change the throttle position.
now logically changing the pump should not have changed anything with the engine, but my thought is that new thermostat raised the temp to its normal temp and this caused something to fail.
my next move will be to check cap, plugs, and fuel water filter, or maybe the starter..
would love to get a mechanic to look at it, but fort lauderdale mechanics seem to be more interested in working on big boats and not returning calls..

 

[Bondo]

Re: 5.0 MPI hard to start after impeller and tstat changed

it doesn't want to start with out melting the battery wires..

Ayuh,.... Welcome Aboard,...

Just My WAGuess,....

Remove, Sand, Clean, Reattach,+ coat with Grease, Both Ends of Both Battery Cables....

Heat from electrical flow is Resistence.....
Your 'puter might be voltage sensitive...

 

[2001SportFailboat]

Re: 5.0 MPI hard to start after impeller and tstat changed

Good catch there, I forgot to mention that the second battery is dead, so I am swapping that one out with a new one, while cranking on the one battery, the gauge drops from 12.5 to 9 while it is cranking, then the smartcraft shuts off. once i stop cranking it voltage picks up to 12.5 again.
I thought i was staying ahead of the game and doing some preventive maintenance.

 

[Don S]

Re: 5.0 MPI hard to start after impeller and tstat changed

It will be hard to start until you get good batteries in it. With a voltage drop below 10 volts you WILL have a hard time starting.
You do realize you should have a "Starting" battery, not a deep cycle because the deep cycle batteries can show too much voltage drop.

 

[2001SportFailboat]

Re: 5.0 MPI hard to start after impeller and tstat changed

Thanks Don.
figures the last thing i was going to replace was the problem! I just installed a new battery, since the neg battery terminal on the old battery was melted. She fired up almost on the first crank this time. doesnt run great still has an alarm and no startup idle but at least she is back to the way she was 2 days ago..

 

[Don S]

Re: 5.0 MPI hard to start after impeller and tstat changed

With an MPI engine. THROW THE WINGS NUT AWAY, get a regular nut and tighten it with a wrench. You are real lucky you didn't destroy your ECM
($1500)

 

[2001SportFailboat]

Re: 5.0 MPI hard to start after impeller and tstat changed

already phased out the wingnuts it just so happened that the new battery came with real nuts, and heavyduty posts.

 

[Bondo]

Re: 5.0 MPI hard to start after impeller and tstat changed

figures the last thing i was going to replace was the problem!

Ayuh,.... Concrats,.... Glad to here it's back up,+ runnin'....

 

[Fishermark]

Re: 5.0 MPI hard to start after impeller and tstat changed

For what it is worth, Mercruiser recommends using either the tapered post connectors or side terminal connectors - as you would use in an automobile. They specifically state not to use wing nuts. I realize that Don S also mentions to get rid of the wing nuts and use a regular nut... but Mercruiser says do not use those connections at all.

(This is from the installation manual that came with my crate engine. Mercruiser installation manual 90-860172030, page 117)

 

[Don S]

Re: 5.0 MPI hard to start after impeller and tstat changed

Probably looks like this, one note, using the stud molded into the terminal is ok as long as you use regular nuts and tighten with a wrench. Those side terminal batteries don't fit battery boxes worth a dime, and are hard to deal with on a boat because there are no quality battery cables of the correct size with the side terminals on them.

PS: I don't think I have ever seen a marine type battery with side terminals.
.
.
.
.
.
.

 

[Fishermark]

Re: 5.0 MPI hard to start after impeller and tstat changed

That's the page!

I too have never seen any marine batteries with side terminals... but they all have the tapered top post. You certainly have much more "meat" to latch hold and give better connection than your typical screw down cable. And, as noted, Mercruiser does recommend using the tapered top post.

 

[2001SportFailboat]

Re: 5.0 MPI hard to start after impeller and tstat changed

I understand what you are saying about the batteries. the new starting battery, has a heavy duty dual terminal on top, so i can connect the starter to the posts instead of the threads. i thought i had a dual battery system, but it looks like the second battery just connects to the selector switch while the other battery is wired directly to the starter.

in my defense i have only had the boat for a month. so i am still learning she was used only a few times a year in the bays of Delaware, barely 50hrs on it but the only real maintenance they (my parents) did was end of season hauling out, drive removal, oil changes and fuel filter."aint broke dont fix attitude" I think that worked fine for the little use that the boat was getting. now the boat gets action a few times a week, i am wanting to get things running perfect, more of the Navy's PMS attitude.
I feel i am on the right track with the parts i have replaced, the S-belt was so worn that she would start sometimes without the belt spinning at all, thermostat was crap too, i think the temp sender is whats triggering the alarm ( 2 beeps ever 2 min but no display on the smartcraft, just a red temp looking icon on the northstar when i move the throttle) and that has changed because now the alarm stops when idling. i have researched 2 senders that function outside the smartcraft system, oil pressure and temp. the northstar does pop up a check engine alarm when starting the engine, and logs a severe or critical alarm, but the smartcraft gauges show nothing. despite the alarm she planes easily with no hesitation but i havnt run at WOT i only throttle to around 3500, since the boat is new to me 20+mph is where my comfort is in the ocean.

back to the thread.. the thought based on your replies is making me think that years of a crappy battery might have screwed up the ECU. I think all i have left to do a my newbie level be a full tuneup, new battery cables, fuel separator filter, and temp sender.. im sure i am missing more obvious maintenance so i welcome any advice. would love to find a good mechanic down here to if anyone knows one. thanks again

 

[Don S]

Re: 5.0 MPI hard to start after impeller and tstat changed

Have you had a chance to visit the Adults only sticky at the top of the page and look at the links? Lots of information there you can use, including OEM service manuals.

 

[chiefalen]

Re: 5.0 MPI hard to start after impeller and tstat changed

Whats easy and can make a world of difference is cleaning ALL the connections.

Disconnect the battery and follow the neg cable to the ground point, remove and shiny clean with sandpaper the cable and the ground bolt.

While the battery is still disconnected follow the pos cable and clean the connections, keep following and cleaning every connection.

Reattach the cables.

When done spray the connections with corrosion pro battery cables, and all the other connections.

Could be the problem bad grounds.

Just my 2 cents it's easy, cost nothing but a can of corrosion pro and you can spray that stuff on anything, motor, to keep corrosion down.

See how it runs after you do what i suggested.

Good luck and welcome aboard !

 

[Don S]

Re: 5.0 MPI hard to start after impeller and tstat changed

back to the thread.. the thought based on your replies is making me think that years of a crappy battery might have screwed up the ECU. I think all i have left to do a my newbie level be a full tuneup, new battery cables, fuel separator filter, and temp sender..

Up till that last part you were doing fine, doing the tuneup and filters and cables yes, but NOT the temp sender. Waste of time and money. Since the temp sender WILL NOT be your problem.
If you go to the Adults Only Thread to the Merc manuals section and download manual 36 (for the 555 ECU), then turn starting on page 1A-35 is a list of what will cause your 2 beeps per min. alarm, and your Smartcraft will not tell you which one it is.
You will need a diagnostic computer of some kind, along with the appropriate service manuals to find out what is causing the alarm.

 

[2001SportFailboat]

Re: 5.0 MPI hard to start after impeller and tstat changed

thanks for the links to the manuals very helpful.and thanks for saving me the temp sender.
it does seem more logical that it is a corrosion issue causing an alarm. from reading other posts the common failures seem to be IAC or MAP sensors, but i am out of ways to diagnose without a mechanics help. my only other clue could be the lack of a cold or fast idle when started up, do these engines have that feature cars do? I have just been assuming its a manual process done by advancing the throttle slightly to warm the engine up.

 

[Don S]

Re: 5.0 MPI hard to start after impeller and tstat changed

Forget what "Common failures" are, or you are going spending a lot of time fixing others problems and not yours.
You need to troubleshoot your system and find out what set off that alarm. It's a fairly easy process with the proper equipment and manuals. Without them, it's hours and days of hit and miss troubleshooting with an ohm meter and parts swapping. Expensive too.
If you want to spend money, get the Rinda Mercruiser Scan too/TechMate. Will do everything necessary to isolate the problem that the very expensive laptops will do. Just takes a little longer. I have one for service calls, wouldn't be without it.

http://216.230.203.183/marine/marine.htm

>
>
>

 

[Gazza1]

Re: 5.0 MPI hard to start after impeller and tstat changed

Here is one on ebay, it could be of some use to you.

http://cgi.ebay.com/ebaymotors/ws/e...8609&ih=014&sspagename=STRK:MEWA:IT&viewitem=