1996 Force 90 bogs under load, runs fine in neutral

[Erik-The-Red]

This is my best friend's boat, a 1996 Glastron w/ a Force 90 outboard. The engine has run great since he bought it about 5 years ago. Just last year it started running a little rough so we pulled the carbs and cleaned/rebuilt all 3 of them, as well as the fuel pump. It has been running fantastic since then, used it all last season and already a few trips to the lake this season.

This afternoon, he was cruising out to our favorite beach on the lake and everything was running like normal. Out of nowhere, the engine lost power and wouldn't push the boat beyond 8-10 mph. If he stopped and put it in neutral, it would rev up to full throttle no problem. But then he'd put it in gear, as soon as the boat would start to plane, it would bog out and only crawl at 8-10 mph again. He had to drive the boat back to the dock at 8 mph which took almost an hour.

It kinda sounds like a fuel issue to me, but I can't understand why the engine would run fine while in neutral at all rpm's but won't run while in gear and under load. I mean, it runs, but it bogs out and has no power. This is an "all-of-a-sudden" issue, not something that has been persisting or slowly becoming worse with time. Any ideas as to where I should look? Thanks for any help or advice!

 

[jerryjerry05]

Re: 1996 Force 90 bogs under load, runs fine in neutral

Look at the fuel system.And you answered your own question:it operates on a NO load just fine.
Check the fuel pump diaphram.J

 

[Erik-The-Red]

Re: 1996 Force 90 bogs under load, runs fine in neutral

Look at the fuel system.And you answered your own question:it operates on a NO load just fine.
Check the fuel pump diaphram.J

I'm not sure how I answered my own question, because I didn't know that a bad fuel pump diaphram would cause the symptoms I described. Thats why I asked questions. We'll go through the fuel system, but the fuel pump diaphram was just replaced last season. I suppose its possible that it has failed already, so we'll look at that too.

 

[moparman]

Re: 1996 Force 90 bogs under load, runs fine in neutral

did you replace the check valves in the fuel pump when the diaphragm was replaced?? do you have an inline filter between the pump and carbs? It's possible to have picked up some trash in the fuel system and passed it through to the pump and on to the carbs if you have no filter in the pump or in line. check it out and keep us posted

 

[TYLER HUNN]

Re: 1996 Force 90 bogs under load, runs fine in neutral

I am having the exact same problem with a 90 hp l drive 1991. I am kinda stumped. please let me know if you figure it out and i will post here if i do.

I just created a post titled L drive 90 hp wont rev past 1800 rpm and bogs out and dies.

I just decarbed it and now its running funny and wont go past 5 mph.

 

[foodfisher]

Re: 1996 Force 90 bogs under load, runs fine in neutral

I'm not sure how I answered my own question, because I didn't know that a bad fuel pump diaphram would cause the symptoms I described. Thats why I asked questions. We'll go through the fuel system, but the fuel pump diaphram was just replaced last season. I suppose its possible that it has failed already, so we'll look at that too.

Takes more gas to push a load as opposed to no load. You're not getting enough gas under load. One backfire can tear a diaphram, rough riding can stir up sediments in the tank to clog the pickup tube, a battery can vibrate onto the fuel line and pinch it. etc-etc Check the fuel supply system.

 

[get me to the water]

Re: 1996 Force 90 bogs under load, runs fine in neutral

I am having pretty much the same issue with my 3.7litre mercruiser. Running great and just out of nowhere no power. I had just rebuilt my carb, but I did notice that when my engine was off the throttle valve would open but once started it wouldn't. I have posted a thread my 192 American ran great for 3 hours then bogged out. Please keep us posted

 

[A.Hoj]

Re: 1996 Force 90 bogs under load, runs fine in neutral

I just went through this same issue with my '98 90hp force. rebuilt the fuel pump, new head gaskets and exhaust gaskets (getting water in the cylindes) still boggs down at high rpm. Finally i pulled the carbs again and found the bottom carb had the needle inlet sticking. sometimes they seem not to stick when you inspect them, but they will on the motor. If they are the rubber tipped ones, chances are the ethanol is causing them to swell and stick in the needle seat. I'm going to replace mine every season along with the rest of the preventative maint. now.