Approximately 225 hours on engine. The weird thing is this didn't start to happen until after the engine was rebuilt with a new long block. Prior to that, never had this problem. I'm going to try the key cycling next and recheck the fuel pressure again and then after that, maybe I will take you up on your offer to try one of those pumps.

thanks.

Scan the motor for codes and look into the history ? Will add from before in my post - you are looking at the ranges for these sensors to be within parameters or out of range - IAC, MAT, Coolant Temp and MAP.

Also internal check valve problem in the fuel pump,

IMO possible fix is in this post.

That's a lot of parts changing - scan the motor for possible help - .

http://www.boatfix.com/merc/bullet/99/99_07.PDF.

OK. Will give that a try as well. Forgot to mention in my earlier post. I also replaced the coolant temp sensor over the winter as someone else suggested prior.

Not sure how the cool fuel works or is plumbed, but this sure smells of a vapor lock condition.

It is, 578 do you vent the hatch when stopped after running ? I asked earlier what engine is having issues, my old 502 mpi was always the starboard side, I think most common is port. ?

It could be possible vapor lock but as posted in post # 1, 2 and 3 almost does nt sound like it.

1 it was past mid Oct in New York - temps could nt even been warm at best, . plus he vents and leaves his engine hatch open after shut down. No report of this problem in the hotter summer months and said never happen before until I guess new long block installed. So what else changed ? Mechanical and or electrical or set up issue ?

2. in post 1 , he Reports advancing throttle helps but should nt have to. I agree you should nt have to. 8 out of 10 times if you have to advance your throttle on a MPI engine to start it or restart it, this can be traced back to an IAC or coolant temp sensor and or its connections and or its wire(s) having an issue

3. cycling the ignition key 3 or 4 times will get the engine started. Motors runs great all day no other problem reported. None of the other engines reporting this problem and he has TRIPS but did not see which engine is the problem one..

I still would scan this motor look for faults and look into the history.

the cool fuel set up is like a GEN II style but has a bigger fuel cooler and designed a bit different.

The fuel pump (electric) in the cool fuel uses the same bracket that needs the heat transfer compound on it to help the fuel pump pull heat away from it. It is wise to clean the bracket completely and reapply new heat transfer compound every so often. Possible check valve problem in the electric fuel pump that lets fuel bleed back or possible some fuel boil off, a slight form of vapor lock. I would not rule out a sensor or connection or wire to a sensor that I listed before. I do not think it was ever mentioned of scanning the engine. You can scan the other engines to compare the results.

After sitting for 2 hours you are saying the engine will start just by advancing the throttle CORRECT that's how I am taking it from post 1. ? If so that is not vapor lock or even a electric fuel pump issue.
.

Thanks BUP. Here's some comments on your comments...

It is the Port engine that is having the problem. It is a 2008 525EFI (at least all of the accessories are; the long block was replaced last August).

1) Problem surfaced immediately after the rebuild with the new long block which was last August but persisted into October when it was quite cool and re-occured this past Sunday when outside temps were in the 60's. Engine temps were quite cool, ie: water temp never exceeded 150*, oil temp stayed around 160*. I immediately raise engine hatches after shut down and leave them open for the 2 hours we are stopped.

2) Advancing the throttle will get the engine to start and once it's started, it runs perfectly normally. The problem is just with the start up.

3) I have not tried cycling the key 3 or 4 times yet. That is next on my list the next trip out. It is the port engine only having this problem.

I have not scanned the motor yet, but I will do that also the next time I'm down there. To reiterate, I have replaced the IAC, cam sensor, crank position sensor, coolant temp sensor, fuel regulator, serviced and flow tested the injectors.

Thanks as I thought advancing the throttle will start the engine per your post # 1. That is not vapor lock nor a fuel pump problem, This boils down to the ECM, connection(s) / connector(s), sensor(s) - Most likely a resistance problem somewhere in the circuit that are related to engine start up. Heat and heat soak can cause resistance problems also corrosion and bad grounds. Just saying.

New sensor(s) installed can still have problems because the sensor(s) all have a 5 V or a 12 volt circuit and a ground. The problem can still be within the circuit rather than the sensor itself. .

Like I said in one of my posts a scan might help about this problem. I would scan all the engines and compare.

Oh also I like your comment about "Here's some comments on your comments" I will use that statement as well for now on.

THanks again BUP... Here are my comments on the comments you made on my comments... LOL..

I have the Rinda / Diacom software on my laptop; will that give me what I might be looking for? I know I can get error codes from that, but what else should I be looking at?