1999 21v - Engine has trouble starting when warm

[406]

Have had the boat for 3 seasons now without any issues. However, this past weekend we were out surfing for a couple hours and then stopped to let the kids swim for a bit and when I went to re-start the boat it had a tough time starting up and seemed like the engine was flooded? It did finally start after a couple of cranks. The next day it had no issues starting when cold but once the engine was good an hot I had the same issue during the re-start. Appears to start up great initially like it always does however, once it is run for awhile it has a tough time starting. Boat ran great all weekend other than the starting issue. Any ideas on where to start? Engine is 350 MAG MPI SKI...SL#OL300094.

Thanks!

[SquibyMcfibbins]

I had this same problem. it turned out to be vapor lock every time here at lake mead where it swelters above 110 degrees. There was even talk of a class action lawsuit about it. https://www.offshoreonly.com/forums/...ck-issues.html Run it hard on a hot day, open the engine before you turn the engine off, and let the engine idle and cool off for at least 3 minutes. If it starts just fine, whereas before it would choke and cough. It's vapor lock. I found it out by bleeding the schrader valve on the black fuel rail just below the cold air intake. it was all vapor and no fuel, and after I put cold lake water on the lines and got the vapor out, it started right up. Other people have said they solved it by moving to a fuel tank mounted fuel pump. I also installed a second blower fan and run it the entire time I'm boating. Hope this helps.

[TeamAllen]

If it is vapor lock, Mercruiser makes a kit to add a second fuel pump. It mount closer to the tank in the fuel line.
Mercruiser has a TSB on it.
https://pdf4pro.com/view/gasoline-en...x-com-4dd4f7.h
Part # 862264A 7 if needed.
https://www.amazon.com/Mercury-Mercr.../dp/B07GD45H2H

[NHarp1]

I have had the same problem the past 1-2 years with delayed starting. Vapor lock? Not sure. I have replaced the fuel pump and flame arrestor with no good results. I run 91 octane fuel. It sometimes takes 3 times turning the key on and off for the engine to fire up. I have a 2016 Raptor engine. The problem appears to be gradually getting worst. Most problems are on hot days but just yesterday I had the same issue on first engine start of the day. This is so frustrating being on the water with the family and the engine just cranking over after 2-3 attempts. Has anyone figured out this problem or having the same issue?.