Rough idle and no start

[XChris1632X]

Serial: 2B121086
2015 proxs 250

Long story but I'll try to give plenty of details.

Been dealing with loss of power and down 500rpm for two years. Been to 2 dealers who have gave it back saying it runs fine. Started thinking I may have tweaked a prop on great lakes. Has run great other than sluggish out of the hole and loss of top speed by 4mph or so.

This last weekend I went on a trip and when I pumped the primer it just felt funny. I pumped it firm and then it got loose a bit but pumped back up. This primer has never taken more than a half squeeze like it always would stay firm. Upon fire up it idled somewhat rough and sluggish. After putting it in gear it started high idling. When I got to the other side of the lake it got worse. Idling at 1300. It would slowly idle down to where I wasn't scared to put it in gear and then drop to 500-650. Eventually it got rough enough I pumped the ball again. After doing that the boat died after starting it again and wouldn't start. Smelled like raw fuel and left an oil slick on the water after trying to start for 10 mins. I let it sit for 15 mins and tried more and still no start. We finally got it to start as I had my buddy pump the ball while trying to start it. We took off back towards the ramp and mid range to high it runs just fine. Immediately back at idle it is rough. Was able to fish for two more days with just rough idle.

Got home and replaced primer ball and fuel line going to the engine as I found the liner of the line rolled up inside the fuel line as the last time I put it together after draining the fuel I did not know the hot water trick. Was suspect of line debris in the pulse pump so I did a rebuild and found nothing. Replaced the filter in front of it just a few weeks ago. Took it to lake test tonight and no change. The new primer bulb seems to not hold pressure like it use to and takes 2 pumps to get back rock solid after shut down. All parts are Mercury OEM.

Any tips? I am supposes to be taking HS boys to Saginaw bay Friday for practice and tournament following weekend and no one can get this in that quickly. I dont want these boys to suffer missing this as this is the big one for them but I'm nervous to go 6 miles off shore.

[Snowedin3]

when you run the engine is it sucking the bulb flat?

[SilverFox579]

Need to pull the fuel filter and check for debris in the VST that may be causing float issues, I'd also replace the pulse fuel pump, OEM parts only.

If is has been a few years since fuel line was replaced you should do this skipping nothing - FUEL LINES AND PERFORMANCE PROBLEMS

[XChris1632X]

Thank you for the reply. As noted above, I did all of those.

[EuropeanAM]

Check for loose or poorly clamped connections between the fuel tank and primer bulb (sucking air).

Bulb should be pumped firm before EVERY engine start, and does not remain under pressure.

[XChris1632X]

Thanks for the reply.

Can you clarify does not remain under pressure?

I always pumped it as a ritual before my boat goes in the water but it rarely was not decently firm already.

[Cougar76]

Might look into tracker diaphragm that controls air to fuel mixture. Just had to replace my second one of these and engine is a 2018 250 Pro XS. First time it started running rough and sluggish and then out on Traverse Bay was running and started shaking and sputtering really bad so I shut it down and would n0t re-fire. Tracker diaphragm got to the point on the first one had a good hole in it. This second time it started idle rough and would get sluggish coming out of hole shot and if wind was correct I could smell fuel when at idle. Low and behold the second tracker diaphragm was going bad. Missed the new 4 stroke by a month when got new boat from Basscat. Hope this helps as I describe what happened to us.

[SilverFox579]

Can you clarify does not remain under pressure?

Fuel is pulled from the tank by the pulse diaphragm pump and needs liquid fuel to function. Very common in summer months for fuel to vaporize in the line between the tank and pulse pump and primary reason for recommendation to pump the bulb prior to every engine start.

[XChris1632X]

Thanks for the continued replies. As an update. I further took the VST completely apart to clean and removed the first fuel pump to verify nothing trapped in the screen. When I put it back together I slowly primed with the filter loose until fuel built up in the VST. I then cycled the key and attempted to start. After 2 tries I got these results

20220611_043426.jpg
20220611_043431.jpg

Ran just as sluggish at idle as it had but fine up top after this. Just struggling to find out where all this fuel and oil in coming from. I don't see how this could be pushed out through cylinders. I was thinking it somehow flooded the VST.

[Snowedin3]

Did you accidentally knock the hose off the internal oil tank or crack it?

[XChris1632X]

It's not oil, it's dirty oily fuel

[BlazerVA]

You should pull your tracker valve and check it for tears. Mine did the same thing last year. Your tracker is on the right and fuel reg is on the left. My tracker went bad then a month later the fuel reg tore. Same exact symptoms as yours with the fuel running down the lower. It would start and idle rpm's jump all over the place.

[EuropeanAM]

Tracker is one of many possibilities- but is one of the more common ones.

Normally at this point, Air/Fuel Pressure tests (recording results at idle, and 5/10/15 seconds after shutdown) are done to determine what areas might need to be inspected.

[XChris1632X]

Just to provide an update it definitely was the tracker valve. Replaced it and engine started running good right away. Until today that is, I blew the compressor. 320 hours.Just wanted to give an update for anyone who later finds this thread.