1994 90 HP Mariner/Tracker Surges and bogs on plane/WOT

[94Nitro170-TF]

Hello all,

I have a problem that just started with me yesterday with the 90HP Mariner/Tracker 3cyl. Outboard on my 94 Nitro Bass Boat, on my fishing trip. The motor is oil injected. We launched the boat mid-day, cranked and ran fine, blasted up river a couple miles, no issues at all ran great. We fished for several hours, and decided to run back down river to another spot, well it cranked, idled, planed out and ran fine, just as normal. We slowed down for a no wake zone, took back off fine, planed out and then several hundred yards down the river it started surging, and bogging down. So I reduced the throttle, and stopped, still idled fine, so I took back off, planed out and again on plane at 3/4-WOT it started the surging and bogged down. I stopped again, this time I walked up on the rear deck and kneeled down and checked the bulb on the gas line and it was still firm.

It acts just like it's starving for fuel or running out of fuel when it gets on plane or at WOT. It still planes out fine, it just starts to surge/ bog when it gets on plane/ WOT. So I got it back to the ramp, loaded it up and went home.

Once at home I put the muffs on it, turned on the water and cranked it up. It fired right up and idled normally. With the motor running, I pulled the hood off the motor and checked the fuel lines to see if I seen any leaks and seen none so I Cut the motor off, and pulled the Fuel filter off to make sure it wasn't clogged, it wasn't and I could blow right through it.

Is it normal for these motors to have what looks like black wire ties as clamps on the fuel fitting connections on the engine?

Anyway I noticed that a couple of connection points didn't even have a clamp/tie on them, they were just slid onto the fitting. One was on one side of the Fuel filter. You could see where there had been one but they were gone. So I went to the Auto parts store and installed some regular clamps on the missing ones. Then cranked it back up and it still seemed to run fine at idle.

Could these missing clamps been my problem? Think it could of been sucking air around those points? I haven't had time to put the boat back in the water yet to see if that cured the problem. My Fuel line with the bulb on it looks pretty old, so I believe before I carry it back out I'll replace it as well with a new one.

I was also told to check the vent tube on the tank, so I'll check it before I go back out too.

Anyone have any ideas on what my problem could be? Anything I can check? I just wanted to check as much as I can before I had to carry it to a repair shop.

Thanks for any advice in advance!!

 

[94Nitro170-TF]

Re: 1994 90 HP Mariner/Tracker Surges and bogs on plane/WOT

anyone?

 

[bobkyle2]

Re: 1994 90 HP Mariner/Tracker Surges and bogs on plane/WOT

i know very little about boat motors but i know if these things suck air they will do some weird things.... as soon as i bought my boat it was sucking air somewhere...i changed all the fuel lines and it had them platic zip ties... i changed them all out for hose clamps...

Hope it fixes yours too

 

[94Nitro170-TF]

Re: 1994 90 HP Mariner/Tracker Surges and bogs on plane/WOT

me too!! I hope the combo of putting the clamps on, and replacing the Fuel line w/ the priming bulb in it will do the trick.

 

[MotorboatinKJ]

Hello all,

I have a problem that just started with me yesterday with the 90HP Mariner/Tracker 3cyl. Outboard on my 94 Nitro Bass Boat, on my fishing trip. The motor is oil injected. We launched the boat mid-day, cranked and ran fine, blasted up river a couple miles, no issues at all ran great. We fished for several hours, and decided to run back down river to another spot, well it cranked, idled, planed out and ran fine, just as normal. We slowed down for a no wake zone, took back off fine, planed out and then several hundred yards down the river it started surging, and bogging down. So I reduced the throttle, and stopped, still idled fine, so I took back off, planed out and again on plane at 3/4-WOT it started the surging and bogged down. I stopped again, this time I walked up on the rear deck and kneeled down and checked the bulb on the gas line and it was still firm.

It acts just like it's starving for fuel or running out of fuel when it gets on plane or at WOT. It still planes out fine, it just starts to surge/ bog when it gets on plane/ WOT. So I got it back to the ramp, loaded it up and went home.

Once at home I put the muffs on it, turned on the water and cranked it up. It fired right up and idled normally. With the motor running, I pulled the hood off the motor and checked the fuel lines to see if I seen any leaks and seen none so I Cut the motor off, and pulled the Fuel filter off to make sure it wasn't clogged, it wasn't and I could blow right through it.

Is it normal for these motors to have what looks like black wire ties as clamps on the fuel fitting connections on the engine?

Anyway I noticed that a couple of connection points didn't even have a clamp/tie on them, they were just slid onto the fitting. One was on one side of the Fuel filter. You could see where there had been one but they were gone. So I went to the Auto parts store and installed some regular clamps on the missing ones. Then cranked it back up and it still seemed to run fine at idle.

Could these missing clamps been my problem? Think it could of been sucking air around those points? I haven't had time to put the boat back in the water yet to see if that cured the problem. My Fuel line with the bulb on it looks pretty old, so I believe before I carry it back out I'll replace it as well with a new one.

I was also told to check the vent tube on the tank, so I'll check it before I go back out too.

Anyone have any ideas on what my problem could be? Anything I can check? I just wanted to check as much as I can before I had to carry it to a repair shop.

Thanks for any advice in advance!!

Hi 94 Nitro: I realize this is an old post but hoping you found a solution. My 94 90HP is acting the exact same way. I replaced the rectifier, stator, trigger, plugs all thinking it might be electrical. It is driving me nuts. Did you figure out the issue!? Thank you for any help!

 

[Texasmark]

On clamps or no clamps, Mercury uses a spacial tie wrap that has a curve in the inside of the female part allowing for 360* compression of fuel lines. If you are talking about lines preceeding the fuel pump, it could matter and no visible fuel leakage around the hoses. If down stream of the fuel pump if it's a problem you will see fuel on the lines. A bad fuel filter was my guess but you checked for that.

Venting the fuel tank is another gotcha that might apply as mentioned but the bulb would be sucked in...you said the bulb was firm.....well when running it's not supposed to be firm. It's supposed to be soft....possibly your fuel pump diaphragm has stiffened over time and isn't pumping like it did when the diaphragm was new and soft. Maybe time for a pump repair kit.
Then there is the question of contaminated fuel, water intrusion, where was the fuel level in the tank when you started having the problem..is there varnish in your fuel line to engine hose?
You can't determine much on muffs as there is no load on the engine.