mercruiser 5.0 issues

Searay176

Cadet
Joined
Aug 16, 2011
Messages
7
HELP!!!!!!! hey peeps of iBoats.... I need to reach out to you to pick your brains about some issues I am having with my 2003 Monteray Montura 228SI with a 5.0 MPI.... OK, this might be a long post cause this is an interm. problem that now has be come somewhat of a day at the lake killer..... ok.... first, after several hours of tubing and wake boarding, we would throw anchor and bob with a beer or two and after 30-45 min..... she wouldn't start,... It would turn over, run extremely rough for a few seconds and the shut off.... it did it several times last year and it seemed to be during the "heat" of the day... thought is was vapor lock at first... but have plenty of gas at shrater valve at fuel rails.... fast forward to this year.... now, its doing the same thing... appears to be maybe heat related.... I can get towed, put on trailer, dive 30 mins to house and nonce here, she will crank and idle and run just fine in the driveway.... next day, put her back in water..... and it starts all over again. NOW today, it did something it has never done before, when gasing to pull a wakeboarder up, she misses, skips, spits and sputters...... idles just fine..... until......she cuts off......... now today, she didn't cool down and re-start.... Had to be towed, tried to crank several times while being towed... it would crank, run idle fine for 4-5 seconds, then almost like it is starving for gas... cuts off.... put it on trailer, tried to start before we left lake....same thing.... drove the 30 mins home...hooked hose to it.... same thing which before would usually start...now... samething...... let is set for 2-3 hrs.... go out... noe starts like a champ idles fine... revs fine.... let engine temp get up to 150 (that's what it runs on lake) and still runs fine.... DO I HAVE A BOAT THAT IS AFFRAID OF WATER???? Some of my weekend mechanic friends say "ECM"...or MAP sensor... or TPS..... I truly don't think its a fuel problem.... seems temperature related electrical..... any of yall have any ideas??? THANK YOU IN ADVANCE!!!!!
 

Searay176

Cadet
Joined
Aug 16, 2011
Messages
7
Re: mercruiser 5.0 issues

Thanks pete... could that be and intermittent problem or if it was a fuel pressure issue... wouldn't it be running bad all the time?
 

Fun Times

Moderator
Staff member
Joined
May 16, 2009
Messages
9,274
Re: mercruiser 5.0 issues

Also do you have your engine serial number handy? How hot is the outside temp getting to in your area right now?
 

Searay176

Cadet
Joined
Aug 16, 2011
Messages
7
Re: mercruiser 5.0 issues

fun times... only about 88 today..... engine temp never gets over 140-150.... Ill look for the serial number
 

Pete104

Lieutenant
Joined
Apr 30, 2011
Messages
1,439
Re: mercruiser 5.0 issues

Thanks pete... could that be and intermittent problem or if it was a fuel pressure issue... wouldn't it be running bad all the time?

You'd think so. But if not getting pressure to run the engine you definitely won't get pressure to start it!
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,480
Re: mercruiser 5.0 issues

Mercury Marine
Serial Number: 0M362843
Model Group: 5.0L MPI 350 MAG MPI MX 6.2L MPI STERNDRIVE
 

Searay176

Cadet
Joined
Aug 16, 2011
Messages
7
Re: mercruiser 5.0 issues

but Pete... It will start and run fine in my driveway right now... I guarantee I can put it in water tomorrow and after a few hours.... she will die.....its done it the last 3-4 times we take it out
 

funk6294

Petty Officer 1st Class
Joined
Apr 26, 2009
Messages
294
Re: mercruiser 5.0 issues

Take fuel pressure gauge with you next time you go out. It could be that your fuel pump is starting to fail and the issue doesn't show up until the boat has been run for a while.
 

Fun Times

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Staff member
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Messages
9,274
Re: mercruiser 5.0 issues

MERCRUISER 5.0L ALPHA MPI DRAIN

Search Results - Crowley Marine

If this is fuel vapor lock then you may have a bad water flow check valve.

You'll want to get familiar with your engine to know what drain system you have on your engine model

Do you have the easy drain like this, Mercury, Mercruiser, Force, etc. - Standard Cooling System(Easy Drain) - 5.0L MPI 350 MAG MPI MX 6.2L MPI STERNDRIVE

Or the Multi Point Drain like this, Mercury, Mercruiser, Force, etc. - Standard Cooling System(Multi Point Drain) - 5.0L MPI 350 MAG MPI MX 6.2L MPI STERNDRIVE

Also do you know if you already have a boost fuel pump installed? It should be inline with your fuel supply hose by the fuel filter. Should look like this, Mercury, Mercruiser, Force, etc. - Fuel Filter And Boost Pump(S/N 0M336102 And Up) - 5.0L MPI 350 MAG MPI MX 6.2L MPI STERNDRIVE

If by chance you have the check valve on the Multi Point Drain (#13), it could be stuck open. If so, there is a chance the hot water from the engine is flowing down to the fuel cooler located under/behind the port side front motor mount and causing the fuel to get hot after turning the engine off when hot.

Try taking a infrared heat temperature gun and test the water hose inline with the fuel cooler on both sides to see if hot water is getting to the cooler area after shut down. Do it on the trailer after a good run.;)

What type/name brand of fuel filter are you currently using? color?

Have you see read what Mercruiser says vapor lock already. http://www.boatfix.com/merc/Bullet/99/99_07.pdf
 

BIGALF

Petty Officer 1st Class
Joined
Dec 31, 1969
Messages
242
Re: mercruiser 5.0 issues

Switch to an aux fuel tank and see what happens.My 5.7EFI just had a screen in the fuelpick up tube that would clog when the fuel slushed in a half full tank. At idle it ran fine since there was no major movement of the fuel in the tank.Took the screen out and it runs fine for the last 2 years. Try easiest fix first!!!
 
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