I have a 1996 28' sea ray with the 7.4 liter MPI engine in it. The boat has just under 400 hours. When I am running about 3000 rpm, the engine bogs down a little (drops 1000 rpms), then seems to release and pick back up. I have thrown in some Seafoam into the gas to try to clean out the fuel injectors, but that doesn't doesn't seem to work. Should I replace the fuel injectors? and if so, it this a 'do it yourself' job or do I need a mechanic to do it?
Make (of engine): Mercury/GM
Model (of engine): 7.4 liter MPI
Changed fuel filter, put in a half a gallon of SeaFoam injector cleaner
Hello,did this problem just start and how does it run above 3000 RPM's?Capt Ron
it started late last summer. Figured it was just bad gas. Have filled up twice this year so far (80 gallons each time), and added the Seafoam with one of the fill ups.
How was the fuel when you changed the fuel filter,any water or excessive dirt.Does the engine run good at higher RPM's then 3000,or does it act up thru-out the entire RPM range?
Fuel filter looked clean. Nothing noticable at all. At idle speed, it revs up, then slows down, revs up, then slows down. It does this all the time at idle speed. It takes about 2600 rpm to get on plane (20-22 mph) and this is when the bogging down becomes noticeable. It continues to happen all though top speed. At slow speeds (1500-2500 rpm) when I am just plowing through the water, it is not noticable.
sounds like a fuel issue,low fuel pressure,do you have the serial number of the engine?
not with me. It is at home.
will need the number to see what fuel system you have,they have sevaral different systems for that year,one with the cool fuel and one with the vapor tank
OK. How do I get back in touch tomorrow once I have the serial number?
just go back on this site,your reply will go to me
The engine serial number is #0F802281
Hello again,ok,you have the VST fuel system,there is a vapor tank with an electric fuel pump and a float,the tank is behind the intake on the top of the engine.We have had some problems with the float inside the VST tank sticking you can pull the top off and check for water and dirt,the water and dirt will be on the bottom of the tank,if there is water in the tank it will cause a surging and not run properly.The top has an o-ring seal,so be careful pulling the top off,clean the tank and let me know how it looks.
30+ yrs. exp. Own a mobile marine shop in SW Florida
OK. Thank you.
Hope this helped,Thanks