72 merc 850 bogs out at full thotle

[thomasomonroe]

My 72 merc 850 starts good idles good and runs good at meduim speed but if I open her up not all the time but often will rev up and boggie for about 30 seconds an then start to loose power and eventuly die. If I slow it down while it is begining to die it will stay running but once I open it up again the same thing will happen. I have tried pumping the bulb while this was happening and it didn't help. I know nothing about working on boat motors were should I start.

 

[Fuzzytbay]

Re: 72 merc 850 bogs out at full thotle

The soulution to your problem lies in finding out, what is not right at higher RPMS. Most high speed issues are fuel related. Not all of course, but I would start there. First off, pumping the fuel ball, will not always help out a fuel starved engine. If you run it up to WOT, and it begins to die, pumping the ball will not save it. You motor will burn up more fuel than the bulb can deliver in a short time. Try this, pump the bulb first, hard at medium speed, then give her some more RPMs, keep pumping, while you slowly bring her up to WOT. IF you can get to WOT, and keep it their for a few moments, then I would say fuel pumps are the problem. If it dies out while doing this, or the bulb will not get hard at medium speed, change fuel lines. Another item to check on the fuel system, is the filter, or filter screens in the carbs. Miss adjusted float bowls can also cause this problem. Keep in mind, a motor that runs lean, ie not enough fuel, can burn out a piston, so be carefull, while trying to solve the problem. Check into the fuel system first, if not, there are a few electrical issues that can cause this as well.

 

[Chris1956]

Re: 72 merc 850 bogs out at full thotle

In addition, make sure the fule line is clean, 3/8" ID and all filters are clean. You may have banjo filters on top of each carb. They do get dirty.