6.2 Mercruiser engine breaking down once it gets up on the plain

[Riviera M370]

Hi Guy's next issue to be resolved on my other boat, this one has an issue once it gets up on a plain. It revs up to 3200 RPM and once it starts to level out on the plain looses revs and power and then a couple of hicups, by then I have pulled the throttle back to idle. I can cruise at 8 knots all day long and no issue but it repeats once back up on a plain at over 3000rpm. I was on a trip down to Mandurah from Fremantle and it was running at 3300 revs for about 2.5 hours then the above happened 2 kilometers from Mandurah.

I only purchased this boat Riviera M370 in Sydney a few months ago and trucked it across Aus to Perth, so I didnt really know how old the spark plugs were so I replaced them, still the same issue.
This weekend I am changing out the ignition leads so I am hoping this will fix the issue.

Is there anything else I can look at to ascertain what the cause is

PS no alarms are present

Engines are 6.2 MCM MPI Horizons Eng S/N OM622243

Thanks Guys

 

[fastimz]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Sounds like a fuel starvation issue. Check all your lines, filters and tank vent, tank pick up....Just a start that wont cost you.

 

[Bondo]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Hi Guy's next issue to be resolved on my other boat, this one has an issue once it gets up on a plain. It revs up to 3200 RPM and once it starts to level out on the plain looses revs and power and then a couple of hicups, by then I have pulled the throttle back to idle. I can cruise at 8 knots all day long and no issue but it repeats once back up on a plain at over 3000rpm. I was on a trip down to Mandurah from Fremantle and it was running at 3300 revs for about 2.5 hours then the above happened 2 kilometers from Mandurah.

I only purchased this boat Riviera M370 in Sydney a few months ago and trucked it across Aus to Perth, so I didnt really know how old the spark plugs were so I replaced them, still the same issue.
This weekend I am changing out the ignition leads so I am hoping this will fix the issue.

Is there anything else I can look at to ascertain what the cause is

PS no alarms are present

Engines are 6.2 MCM MPI Horizons Eng S/N OM622243

Thanks Guys

Ayuh,.... Change the fuel filters, 'n Inspect the contents of the 1s on it now for water, or crud...

 

[Silvertip]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Anti-siphon valve, fuel pump, carb need cleaning to name just a few potential problem areas.

 

[Don S]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Does the audio alarm system work on the boat? You should hear a single beep from the alarm when you first turn the ignition on.

There are some faults that can reduce the engines rpm, but they an alarm that goes with them.

 

[Hoosmatroos]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

No carb, it's a MPI

 

[Riviera M370]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Don the alarm does sound on ignition on.

I have now changed over the fuel check valve from this engine to the generator fuel line. When I read Silvertips comment I remembered that they were supposed to replace this when I inspected the boat originally. When I checked it in fact had not been replaced so I am hoping this is the problem, however ew have 4 metre swell and really strong winds today so I will test drive the boat tomorrow.

I have also ordered fuel filters to replace when they arrive.

Thanks for the tips

 

[bentheredengthat]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

I had an intermittent problem just like (cutting out on plane) this that no one could ever figure out. I thought I had all the problems that everyone has listed above & so did my mechanic.

I had the engine idling one day & brushed against the 2 small wires plugging into the side of the distributor cap & the engine cut out just like on a test run!!

So also try moving your wiring around while it's idling & see if maybe you have a partially broken wire somewhere.

 

[LorenHaus]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

If you dont have access to a code scanner, I would start by hooking up a fuel pressure gauge and taking it for a test drive. If you dont have a pressure gauge, just run up to a AutoZone or some other auto parts store. Most will rent a gauge kit out for free (deposit required) or a minimal chage. Check for consistent fuel pressure watch closely and note pressure at idle and then note pressure when you are revving the engine to the RPM that you noticed an issue before. This needs to be done under a load in the water, not just on muffs in the driveway. Lack of CONSISTENT fuel pressure is often the cause of issues like this. Sure it could be electrical, or mechanical but more times than not it is pressure related.

Like others have said, change the fuel filter, check for kinked send/return fuel lines going from the fuel filter housing to the fuel pump, etc (unless you have gen 3 cool fuel.....a big rectangular box on the lower starboard side of your motor....sorry i didnt have a chance to look up your s/n as I'm at home right now, not at Michigan Motorz ......)

 

[Riviera M370]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

I tested the boat today and unfortunately the problem still exists after changing the anti -syphon check valve. This time the boat got up on a plain and didnt break down until I backed the throttles off and then at around 1500 RPM she started to lose power again.

I will change the fuel filters this week and also change the igntion leads as I have new ones.

I will also hook up a crystal pressure gauge as I have access to those to check fuel pressure

 

[achris]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

I have a laptop with the Merc diagnostic software. If you can wait until I'm home (mid May) I can come down and plug in and see if you have any codes set....

Send me a PM around the 12th to remind me....

 

[Riviera M370]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

I have a PC with the Merc diagnostic software. If you can wait until I'm home (mid May) I can come down and plug in and see if you have any codes set....

Send me a PM around the 12th to remind me....

Thanks achris that would be fantastic, hopefully I will have this sorted by then

 

[Riviera M370]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

The saga still continues. I have checked all fuel lines for blockages, swapped anti syphon valve replaced all fuel filters (fuel tank and engine) and I still have same the issue.

I have a spare Gen 11 fuel pump and cool fuel cooler from my 4.3 so I am going to try this out, but I figured if I had an issue on the engine side of the pump I would get an alarm at the very least

Any other suggestions, as I am getting bored driving the boat around the places at 8 knots, need to be able to open the taps up every now and then.

 

[achris]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Hang in there.... I'll be home in about a week....

Chris.......

 

[dubs283]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

have you inspected the cap/rotor??

those mpi flat caps are notorious for corrosion issues, esp. in salt water

 

[Riviera M370]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

have you inspected the cap/rotor??

those mpi flat caps are notorious for corrosion issues, esp. in salt water

No I havent done that yet, I have however replaced the spark plugs and ignition leads. The boat doesnt miss a beat at low speeds no matter how long its operated for, nor when its given full throttle until about a minute (or maybe a little less) at set throttle position, much like running out of fuel. The engine starts to lose power the revs drop off and once I back the throttle off its fine at 8 knots or less and no alarms.

 

[dubs283]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

check under the cap

you will be surprised how corroded the contacts are

in fact there is a service bulletin concerning replacement caps from mercruiser, a couple seasons ago there was a string of bad flat caps that were arcing between #3 and #7 contact posts - the problem has since been rectified, all the new flat caps are good - something to keep in mind

 

[NHGuy]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

So after you complete the tune up stuff it could still have the issue. If it does it's possibly the fuel pump. As an earlier poster said, monitor your fuel pressure at the higher loaded rpms. When you get the problem I'd bet your fuel pressure is low, maybe below 30. GM auto & truck fuel injection systems need 45 PSI, I'd imagine the marine efi would need at least that too. If the pump isn't flowing enough fuel the pressure will fall off under higher demand.

 

[Riviera M370]

Re: 6.2 Mercruiser engine breaking down once it gets up on the plain

Hang in there.... I'll be home in about a week....

Chris.......

Thanks heaps for today Chris, you have solved me some major time on the trouble shooting of my issue>

Thanks Again