2.5 mercury afraid of water

**NICE PAIR** · 07-01-2018, 09:45 PM

Originally Posted by Kwa

Hey fellows, me again with update. My 40 year mercury mechanic called sat. to give update. He replayed back to me everything I've been saying all along, floods after it's been run and sits for 30 minutes or so. Yes he does see what it's doing. He has checked and rechecked everything that has already been checked and rechecked. Don't have a clue what is causing it to flood. He's checked fuel pump,diaphragm, vast, vents, checkvalves, stator,spark,fuel pressure, ecu. So, what do you do now??

On the 2.5 motors there was a tee in the pressure side of the system that had a very tiny hole in it, it was there to bleed off the high pressure from the injector pump so the motor wouldn't flood.

When you shut the motor down you have 39 lbs. of fuel pressure between the pump and injectors, my foggy brain says there may be some type of pressure relief like it in the vst tank to bleed off the high pressure. (it's been a while) $ .02

**Kwa** · 08-18-2018, 10:14 AM

Hey fellows, thought I would let you what's been going on AND that I'm not absolutely crazy. The " 40 yr mercury mechanic " has had my boat for a little over 2 months. Stumped, lost, does not have a clue what's wrong.

**Merc 2.5** · 08-18-2018, 10:56 AM

I would swap out all electrics, if he has ex parts ,ask if he will start swapping stuff around

**Motv18** · 08-20-2018, 10:14 AM

What color is the smoke.

Choke position/ cold start position

oil removed?

flooding heavy smoke generally comes from a choke/advancing throttle. Efi is different from carbs but the ecu will enrich if automatically or directed by a switch depending on system. Any physical parts can stick if hot and also do it. Efi cars have a clear flood mode.

Wot cuts injectors and clears flood, 1/2 chokes and floods or starts what ever happens first. Why it’s included on efi that run without touching the throttle is beyond me.

**Kwa** · 08-23-2018, 12:00 PM

Give up!! Looking a used engine and IT WILL NOT BE A MERCURY..

**bullet123** · 08-23-2018, 12:06 PM

did you ever swap temp sensor like rock said in post #8?

**bullet123** · 08-23-2018, 12:21 PM

One sensor on side of EFI, has two brown wires-part#13221T01. Other sensor on port head-part#13536A6. Not expensive. Maybe borrow them off of a buddies motor?

**rock** · 08-23-2018, 02:20 PM

How much money you want for that worthless pos Mercury that don't run right?

Rock

**bullet123** · 08-23-2018, 06:29 PM

I think I have a temp sensor for side of efi and a tps I can send you if you want to try them.

**tlwjkw** · 08-24-2018, 04:00 AM

checked tpi readings when its hot?.. if vst has a problem with something stickin' ya get fuel outta tha little hole in tha fitting on tha plenum..

**pjbrownva** · 08-24-2018, 12:34 PM

Originally Posted by Kwa

Hey fellows, thought I would let you what's been going on AND that I'm not absolutely crazy. The " 40 yr mercury mechanic " has had my boat for a little over 2 months. Stumped, lost, does not have a clue what's wrong.

With all due respect, you need to find a new mechanic.

First, the mechanic certainly didn't work on it non-stop, not even 1/4 time for two months... that would mean 80 hrs of labor!

Second, he obviously knows how to work on Mercs if he's done it for 40 years, but that doesn't necessarily mean that he's good at understanding or diagnosing the more difficult problems. There's a lot of good advice on this board and especially in this thread. If you have the time and the inclination to buy some (used) parts, and turn a few wrenches yourself, I'm sure you'll be able to fix it.

A few of the guys on here have even offered to lend you some parts, so that you can swap them and see if it fixes your problem... presumably you'd send them back, along with an Amazon gift card as a small thank you if the swap doesn't fix your problem, and everyone would be happy -- I doubt they'd ever ask for the gift card, but it could keep up the exceptionally good will.

If you do decide to part with the motor, consider giving one of the guys on this forum a shot at it. I'm sure it would go to a good home and be well loved by it's new owner.

Heck, if I had the ca$h available, I'd even make you an offer. A 2.5 EFI would be a sweet upgrade from the current 2.0L 150 Carb that I'm *almost* finished repairing!

Anyway, good luck with the motor... and I love Scream and Fly, there is so much knowledge and sense of community here, it's truly a good thing and a real asset.

-Phil

**bullet123** · 08-24-2018, 12:47 PM

I would only request shipping costs. 2.5 Mercury’s are very good motors. Hate to see them leave a bad taste in your mouth, but if you give up. Post it for sale on this board.

**Motv18** · 08-24-2018, 07:50 PM

If the merc has the relief exhaust valve it might stick closed/open when hot.

One symptom of this is mentioned in a post starting on land but not easy or starting at all in water.

Aftet running to a fishing hole, when you come off plane does it run a little shety if so next time out stick your hand on the hole in the mid above water. You should have a good strong pulse coming out. If not and it’s gurgling water like a monster drowning. The flaps stuck.

**rock** · 08-25-2018, 07:12 AM

To my knpowledge all 2.5 Mercs have the exhaust relief but it is not a valve or flap. Exhaust enters the adapter plate at the rear starboard side and transfers thru the plate to the front of the motor then across to the port side and to the rear of motor then out the rubber boot to the atmosphere. When plugged the motor will struggle in the water but run fine on a hose. I have seen several plugged solid but it will have the same plugging effect hot or cold.

Rock