2010 H210 - Merc 5.0 mpi Stalling Out

bradsimpson301 · **Posted:** Tue Aug 18, 2015 3:07 pm

Hey - We purchased a 2010 H210 with 16 hours on it at the beginning of this summer. We now have just shy of 50 hours on it boating primarily at Deep Creek Lake, MD and the Three Rivers of Pittsburgh, PA. My problem: when cruising at 3000 - 4000 rpm and backing off to idle, as soon as I put the Merc into neutral, it revs up slightly and then stalls out. The frustrating part is that it does not happen every time, it's inconsistent. The dealer put their laptop on the motor and it showed no fault codes. He suggested that I run the blower all the time. I do. It still stalls out - sometimes. Has anyone experienced this problem or does anyone have any ideas or advice. The dealer will look at the boat (I have nothing but good to say about them); but, I have to leave it there for a week or so. Any ideas? Thanks in advance!

GottWhat · **Posted:** Tue Aug 18, 2015 3:38 pm

Welcome to the forums, sorry about the issues you are having with the boat. Did the dealer do anything else to diagnose the problem?

PS: We bought our Cobalt 246 this spring from the original owner who kept it on Deep Creek Lake...was too cold for us to really explore the lake but looked like a great place.

jayjay4735 · **Posted:** Tue Aug 18, 2015 5:31 pm

This could be way off, but out of curiosity, how is your oil pressure when you stop cruising and go to idle? I know that on my old engine there would be times when, after cruising for a while, if I went to idle, the oil pressure would drop to the point of the alarm coming on at very low rpms (when it would need an oil change). Is it possible your engine has an automatic shut off when pressure drops below a certain level?

JeffLW · **Posted:** Tue Aug 18, 2015 6:40 pm

Does it start right back up and idle fine?
I had an issue with my Merc 5.0 stalling when put it in neutral when I first got it and it turned out to be a sticking IAC valve.

Thalasso · **Joined:** Tue Jan 18, 2011 8:45 pm **Posts:** 333

Curious who your dealer is?
Are you getting any beeps? (Alarm)
Run your blower?
The only thing that should be running is you and that should be to find another mechanic.

LouC · **Posted:** Tue Aug 18, 2015 7:52 pm

I'm assuming this is an EFI engine, right?
Not all FI faults will set an engine code ...
So you need to understand how it works to fix it and not just throw parts @ it..
You can start with:
Clean throttle body
Check IAC valve
Check for vacuum leaks (intake manifold gaskets, throttle body gasket)

If you want to do your own work consider getting a Merc shop manual and learn the right way from the beginning...

schoolsOut · **Posted:** Tue Aug 18, 2015 8:16 pm

+1 for cleaning throttle body. I was having a similar problem. Boat would run great, but occasionally shut off when the rpm's dropped quickly. Also when starting cold it would rev, then drop, then shut off. It was also starting fairly slowly. I cleaned the throttle body and it has not acted up since. I would be a little surprised that it needs it already after only 50 hours, but that would be an easy place to start. If you do a lot of idling (maybe driving at no-wake speeds), it could get gunked up more quickly.

jayjay4735 · **Posted:** Tue Aug 18, 2015 9:08 pm

Are the injectors in an MPI engine as easy to clean as the throttle body of an EFI engine? After re reading the post though it certainly seems possible that a boat that is five years old with only 16 hours on it when you bought it could have problems with the fuel system.

bradsimpson301 · **Posted:** Wed Aug 19, 2015 8:55 pm

Thanks for all the quick responses! I never noticed the oil pressure drop until after it stalls out, obviously. I believe that is what the solid beeping alarm is trying to tell me. Yes, the 5.0 mercruiser is fuel injected. It always starts right back up. Hopefully that answers a couple questions that came up.

I think I'll start with the throttle body cleaning and go from there. The boat is in dry storage now. Hopeful to be back on the water Friday or Saturday. I'll update with my results!

bradsimpson301 · **Posted:** Mon Aug 24, 2015 10:17 am

Quick update after a weekend of boating: I did not have a chance to clean the throttle body. The problem occurred several times - a couple while docking, which can be a little of a pain in the a$$. The boat always starts right back up. I watched the oil pressure and it stays consistent above 40.

Sometimes it seems like it revs up slightly right as I disengage forward direction and it goes into neutral. It's frustrating. I put Lucas Oil fuel system cleaner / fuel injector cleaner this tank, so we'll see how that works.

The H210 had 16 hours on it when I bought it and now has 49. We're using it and everyone is having a blast. I need to get it to the shop; but just don't want to miss out on the last several weeks of summer. Thanks for all the ideas and anything else anyone can provide! -Brad

bradsimpson301 · **Posted:** Sun Aug 30, 2015 4:30 pm

Throttle body clean. It didn't look that dirty to begin with. How do I check and/or clean the IAC valve? I know where it is, but don't want to start disassembling things if I don't have to. Also, where can I find a Mercruiser service manual? I'm also looking for a 2010 Four Winns H210 owners manual. I got one with the purchase, but it got wet the first weekend. (New boat, rain, forgetting the owners manual is on the floor) I looked on the four winns website and the year and model isn't there....? Thanks, Brad

GottWhat · **Posted:** Sun Aug 30, 2015 7:11 pm

I can see if I have the manual for your boat. What is the serial number of your engine? Send me a private message with the SN and your email address and I will see what I can do.

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

Just typing out loud here...when you put the boat in neutral it activates a switch-relay that kills power for a split second....this helps gears in drive engage/disengage under no load. It seems odd that yours is revving then shutting down. I'm wondering if that relay may be at fault....maybe its hitting neutral before the split second shut down which could account for the rev, then killing electrical too long that causes the stall.

Just something to ponder as I've never had that issue. Others yes but not that one.

LouC · **Posted:** Mon Aug 31, 2015 7:53 pm

That is the shift assist, which is needed with outdrives that use dog clutch shifting like the Alpha and Cobra.
The way it works is that when you try to shift to neutral the dog clutch wants to stay engaged because of pressure on the prop. When you try to shift it puts pressure on the shift cable jacket. This force is transferred a movable plate the engages a switch that cuts the ignition for a split second. This lowers the idle and allows the dog clutch to release.
If you get stalling only when shifting it can be a sticky lower shift cable keeping the shift assist engaged too long.
If if it only stalls when you bring it back to idle in gear it's probably not that.

bradsimpson301 · **Posted:** Tue Sep 15, 2015 5:26 pm

Hey, I want to change the IAC valve before I put the boat in the water this weekend. It seems like the IAC valve comes out easy enough; but, does anyone have a part number - or better yet the part number of an automobile equivalent that I can get at my local NAPA? All the online and shared mercruiser manuals are for up to 2004 or 2007. The serial number range given for the 5.0 mpi in the available manuals does not match my serial number. Below is the tag on my motor.

Motor Info:

We want to make the most out of whatever's left in this Southwestern PA summer. Thanks for any help provided!

www.iFourWinns.com

2010 H210 - Merc 5.0 mpi Stalling Out

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