Mariner 150 power issue

**rato65** · 05-21-2016, 02:45 AM

Hi there,
I am new here ( and also to boats...) and hope to find a hint after searching now for couple of days the cause for a power loss on my Mariner V6 150. Infortunately I did not find the model number except a little silver plate with a number that seems not to be the usual code B122040 with a big M below. I assume it is a 1986, but not sure. It has "B Carburetor" and "Advanced Fuel Injection". I bought this last year, only checked run in idle and water cooling onshore. Seller has sated that it stood for 3 years.

The issue:
Starts very well, runs smooth in neutral and without gear up to 6000. When gear in, runs in idle good. As soon as I start accelerating, it drops down in rpm and cuts off. When givin full throttle in gear, it gets up to 4000 and holds, but as soon as I move throttle down a little same problem, gets down and cutoff. Amazingly, it starts very well immediately after, each time.

What we checked already:
- compression 100 on 1, 108 all other cylinders
- all new sparkplugs (those with ring electrodes, dont know the engl. word)
- carbs taken apart and cleaned with cleaner and ultrasonic (litle dirt)
- both fuel filters cleaned (very dirty)
- tried electric fuelpump bypassing original
- fuel pump had slacky membrane but otherwise ok, changed membrane and tested fuel output, good pumping
- new tank, fuel and ball connected directly to filter behind fuel pump
- checked sparks visually
- measured stator - one line was 50ohm instead of 90
- checked timing ok at different rpms (when reached)
- took carb air cover off and sprayed fuel directly into the carbs, when mid rpm drop down, immediately gave much power
- disconnected all fuel supply to check if carbs contain enough fuel and let run for minutes

We think it must be fuel supply or some sort of adjustment (although jets are notadjustable,or are they) - but have no idea anymore what to check else than we did. Does anyone here may have had such an issue or can give some ideas what we could do?

Thanks very much for any comments!
Cheers
rato

**CrankB8** · 05-21-2016, 07:47 AM

Did you check the float levels in the carbs?

**rato65** · 05-21-2016, 08:05 AM

Originally Posted by CrankB8

Did you check the float levels in the carbs?

Other than roghly checking visually when the carbs were off - no. How would I do that correctly?
One addition - all testing with gear in was in water under load.

**CrankB8** · 05-21-2016, 01:42 PM

I typically piddle with Johnson/Evinrude, but I remember some Merc carbs floats moved freely in the bowl. Some were known to deteriorate pretty bad. Not sure which ones you have, but I would visually check the floats, and if you remove the carbs, turn them upside down and blow air into the fuel inlet to make sure you are getting a proper seal with the needle/seat.

**TEXAS20225** · 05-21-2016, 02:11 PM

could be stator low side out

**rato65** · 05-22-2016, 03:04 AM

@TEXAS20225 - thanks for reply.
Ok, I think we do that measurement again. I remember there was a little lower resistance on the red/white wire, but unfortunately I did not note down, I think it was a 50 reading instead of 90 that should be. we though it is ok and not such a big difference. i will check again to be sure.
@CrankB8 - thanks for the description.
We had the carbs taken apart and I think we have done what you said, and checked with fuel and the swimmer levelling out holding in hand.

**j_martin** · 05-23-2016, 10:07 PM

Originally Posted by rato65

@TEXAS20225 - thanks for reply.
Ok, I think we do that measurement again. I remember there was a little lower resistance on the red/white wire, but unfortunately I did not note down, I think it was a 50 reading instead of 90 that should be. we though it is ok and not such a big difference. i will check again to be sure.
@CrankB8 - thanks for the description.
We had the carbs taken apart and I think we have done what you said, and checked with fuel and the swimmer levelling out holding in hand.

Take a relatively small amount of the money you're about to throw at this thing and buy the proper meter (DVA, I think) to check the stator output voltage at the switchboxes. A single shorted turn won't even show up with an ohm meter, but will kill the output.

Your description of the action sounds like a stator problem.

**CrankB8** · 05-23-2016, 10:12 PM

Totally agree. As stated before, a DVA adapter plugged into your multimeter can tell you a lot. Pick one up on eBay, then check CDIs website on their troubleshooting, or. All their tech guy. That are more than happy to help. I've used them a ton.

**rato65** · 09-24-2016, 01:52 PM

Don't know if this will be read since the thread is a few months old. However, I measured the stator, Ohms said already values were not ok between red and blue and all to ground. So changed stator with a new. Put in water and still almost no change, however stall only when accelerated slow from idle to about 2000 or 2500. Fast move to WOT and engine keeps running, but only a part of the hp it should have. Measured with a DVA adaptor the output from the CDIs, they went from 140 to 250 on all 6 outputs.checked compression again, put in cleaner and oil and let it settle for a day, after that all 6 between 118 and 122, so good in my opinion. But still stalling engine under gear and accelleration. Today I disconnected the Idle Advance Module and read half a day about timing and sync. So went to the pier again, and tried to increase the primary pickup a little until it starts bogging in idle. few turns back and now it did not stall anymore, regardless of rpm and reate of throttle change. This was just a trailer test with engine in water, tomorrow boat goes in and....i hope that will be a start.
ANyway, what is your opinion here - this was without timing lamp, did not have one. What would be the next to be sure th engine is not having another issue which I maybe just biased by this procedure.
thanks in advance!

**rato65** · 09-27-2016, 03:15 PM

So now it runs - at least this evening I went through all speeds and throttles and the motor is still running and my smile is broad...yeees. However, now I see the phenomenon I read in other threads that at full speed the temperature goes up to max fast, and almost as fast down after slowing down to 3500 or 4000. I measured with a laser and see 83 deg Cels, so like 180 F, at WOT. No boiling pee, but yes, some steam. Thermostats are out (just observed). Do I have to worry seriously now?