Mariner EFI hot start issue

[Sheps78]

Have a '97 mariner magnum 150 EFI. Motor starts fine when cold and runs great but if I shut down say after running back to the dock to load out when I come back to start it to trailer I have to crack the throttle halfway for about 10-15 seconds and ease off to keep it running (also smokes like a freight train and idles rough during this process) but once I take off it runs great and idles better after being opened up. This only happens when the motor is warm if I fish for 45 minutes or so it usually fires right up. I just replaced the spark plugs and they all looked really good. Been reading that I may have a bad check valve in the oil injection system. Wondering which one I'm looking for? Tracing the oil lines from the remote tank one runs to a fitting on the bottom of the block(parts diagrams says pulse fitting) and the other to the 3 way tee and then the small oil tank(only 2 lines coming off this fitting bottom is open). According to parts diagrams this is just a vent fitting and the only one that actually says check valve is the one on top of the fuel filter housing but that doesn't seem like that one could cause oil to be pushed into the fuel to me. Thanks in advance and I apologise I'm unable to add a picture of what I'm looking at.

[alli ss]

You have heat soak. You need a new water pump, thermostats, rebuild the poppet valve and flush the block extremely well. Try letting your motor idle for a minute or so after a run and see if it helps. If so follow my advice above.

[Sheps78]

Appreciate it! I Put a new water pump in this spring

[alli ss]

Replace the poppet valve kit and thermostats then. Did you replace the metal liner in the water pump housing and the wear plate below it?

[BMCD]

The smoke though sounds like your running rich, i think your on the right track. Might post in the merc forum to get more traction. Always a good idea to check thermostats and the poppet valves.

[Highcentered]

Make sure to post the serial number if you post in the Mercury forum otherwise the only answer you'll get is to read the "before you post" thread at the top of the page.

[alli ss]

The smoke is from the gas cooking off in the fuel rails from heat soak leaving more oil than gas

[Sheps78]

Will definitely take a look at the poppet and t stats, motor had sat for awhile and the pee stream at idle was weak the first couple of trips even after replacing impeller but the last 2 times out it had a solid stream at idle. Always has been strong when on plane

[alli ss]

Next time you go fishing, after a run let it idle while you get your stuff ready like 1-2mins and see if it helps then let us know

[Sheps78]

Will do hopefully this weekend

[Sheps78]

This is probably a stupid question but where exactly is the poppet valve? Thermostats are right on top of each head

[alli ss]

This is probably a stupid question but where exactly is the poppet valve? Thermostats are right on top of each head

No dumb questions. It is located under the skirt between the cowling and midsection. It is a flat plate, figure 8 shaped. It is on the starboard side of the motor (drivers side)

[alli ss]

2B57663B-83EE-4B82-A84A-B0EC2A2570AA.jpeg

you can see it here with the cover off right under the switchboxes. Look for a water hose going into a removable cover

[Sheps78]

Sorry it's been awhile since I got back with you. I put in a new fuel line/bulb and new fuel filter and took it out last week and it did great air temp was 65-70 and water was about 80*. Went out this afternoon water was 80* and air temp was 80-100* this afternoon, boat gave me trouble after running again without idling. When we left i took it real slow through the no wake zone back to the ramp and shut it down, took about 15 minutes in line to get my trailer in and the boat fired right up and did every time we fished a spot for at least an hour so will definitely put new tstats and poppet in.

[alli ss]

Thanks for the update. Keep em coming

[Sheps78]

Will do it will probably be another weekend or 2 before I get to run it with new parts

[James john]

Have u replaced all ur fuel lines already? We been seeing a lot of hot start issues no matter grand and it’s been fuel lines normally

[lpugh]

Would be in your best interest to post this on the 2.5 L mercury forum and be sure to include your serial number, You will get better more accurate info there
Without the required info many will not even respond to the post

[Sheps78]

Got a new update on it put in new tstats and flushed the block through the flush plug for 10 minutes and still no change idling for a couple minutes does seem to help though. Pee hole stream was noticeably better at idle today. Will go ahead and get a poppet kit ordered and probably replace below deck fuel line I just did the bulb and it's hose