2001 90hp Crank Issue

[sbfishy]

Hey guys,

I just had my motor serviced and fuel pump/lines replaced less than a month ago. My issue is this: I get on the water, motor cranks perfectly fine and can be cut on and off all morning without issue. Then I go to make a run somewhere in the middle of the day and the motor won't crank. At first I thought battery was the issue as the livewell and graphs had been running all day, but voltage checked out ok. Now I'm thinking it sounds like it's not getting fuel. After about 20-30 attempts at cranking, she will finally sputter to a crank after holding the key in to crank for about 20 seconds. After that problem, I can make a run, turn her off, fish for awhile, then when I go to crank her again, she cranks fine for the remainder of the day. This has happened to me two weekends in a row (during tournaments nonetheless). In the middle of the day, she won't crank that one time, and every other time she cranks fine.

Motor is a 2001 Mercury 90hp 2 stroke.

Any ideas?

Thanks,
Steve

 

[achris]

Re: 2001 90hp Crank Issue

Hi Steve,

If the engine is not cranking (not turning over when the key is turned to START) then have a look for loose/dirty battery terminals or loose/dirty/corroded wires in the start circuit, starter motor, solenoids.

If the engine is cranking fine, but not firing, check for fuel, or a loss of spark. Before we can proceed, you need to know what's causing the problem, bad electrical connection, lack of fuel or lack of spark.

If the engine was serviced and the fuel line replaced (why?) then that might be a place to start. Have the PROPER fuel line ty-wraps been used, or are they just normal wal-mart types?

Chris.......

 

[sbfishy]

Re: 2001 90hp Crank Issue

Thanks for the reply. I should clarify, the engine cranks fine but does not fire/start during the time of my problem. Again, it will start just fine most of the day, but it has that one random hiccup midday. I'll have to perform a spark test this weekend and I'll check the fuel system as soon as I can. The fuel line and pump were just replaced because the pump was old and diaphragm was leaking as were some of the fuel lines. I would think the proper equipment was used as it was done by a certified mercury mechanic, but I will check as soon as I can.

 

[achris]

Re: 2001 90hp Crank Issue

Thanks for the reply. I should clarify, the engine cranks fine but does not fire/start during the time of my problem. Again, it will start just fine most of the day, but it has that one random hiccup midday. I'll have to perform a spark test this weekend and I'll check the fuel system as soon as I can. The fuel line and pump were just replaced because the pump was old and diaphragm was leaking as were some of the fuel lines. I would think the proper equipment was used as it was done by a certified mercury mechanic, but I will check as soon as I can.

I have pulled so many normal ty-wraps off fuel lines I lost count YEARS ago, and these were also done by 'certified' mechanics...

This is what you're looking for on the ty-wrap....

 

[sbfishy]

Re: 2001 90hp Crank Issue

Just checked today. They are the proper fuel line cable ties as shown in your picture above.
Possible side note, as I was under the cowl today, I noticed that very little oil had been used after last weekend. Being a 2-stroke, I normally have to add oil nearly every outing, but this time it's full after running a tournament all day (6 am - 3 pm). Perhaps this is a possible symptom or maybe I'm just overreacting on this?

 

[kmagnuss]

Re: 2001 90hp Crank Issue

FYI I have the same motor and a tank of oil (about 1/2 gallon) lasts me 40-50 gallons of gas easy.

 

[achris]

Re: 2001 90hp Crank Issue

... I noticed that very little oil had been used after last weekend. Being a 2-stroke, I normally have to add oil nearly every outing, but this time it's full after running a tournament all day (6 am - 3 pm). ...

How much petrol did you burn during the day? If you are using way less than you would normally expect, then check the linkage and operation of the oil pump. If the linkage has been dropped off, then you're not getting enough oil at the higher engine speeds....

Chris.....

 

[Dave1027]

Re: 2001 90hp Crank Issue

FYI I have the same motor and a tank of oil (about 1/2 gallon) lasts me 40-50 gallons of gas easy.

That would be 80 to 100 to one mix. Sounds too lean to me. I would think something closer to 50/1 would be better.

 

[achris]

Re: 2001 90hp Crank Issue

That would be 80 to 100 to one mix. Sounds too lean to me. I would think something closer to 50/1 would be better.

Yeah, agreed if he's running around at higher throttle settings. But at idle and low speed... About right. If I remember correctly, the ratio for those pump is 80:1 at low speed increasing to 50:1 at near full throttle...

Chris..........

 

[Texasmark]

Re: 2001 90hp Crank Issue

Yeah, agreed if he's running around at higher throttle settings. But at idle and low speed... About right. If I remember correctly, the ratio for those pump is 80:1 at low speed increasing to 50:1 at near full throttle...

Chris..........

You are correct sir. (Where's your Bertram Avatar?) The manual states that the oil tank is 1 gallon with 1 quart of that in reserve after the warning beep commences. It also states that approx run time at WOT is 6 hours. Running the calcs on 3 quarts at 50:1 equals just under 40 gallons of gas. So, as a side note, if the 6 hours run time is based on 3 quarts then it admits to a WOT consumption rate of 6.7 gallons per hour. And, why wouldn't it. Would you run your tank empty listening to the horn for the last 1/4 of your run time and subject your engine to a powerhead seizure? I don't think so. I wouldn't.

A lot of knowledgeable guys on here use that it's 10% of the HP as a general rule. I knew my 90 did better than that. Besides that's a general rule for all engines of every usage application. I never ran the numbers till now and yes, it's in the manual, it does run better than that.

You can thank OMC for most of that by loop charging their midrange engine back in 1968 with the Rude Triump 55....forget what they named the Johnny. It was time as the cross flow 2 stroke of the day just loved the gas pump. Once the patent ran out Merc sucked it up with their new 3 cyl product line.......the exhaust back pressure for a 3 cylinder works for the looping equation. That's why the 3 cyl and dual 3 cyl (V6 engines) became popular with OEMs.

Mark

 

[sbfishy]

Re: 2001 90hp Crank Issue

How much petrol did you burn during the day? If you are using way less than you would normally expect, then check the linkage and operation of the oil pump. If the linkage has been dropped off, then you're not getting enough oil at the higher engine speeds....

Chris.....

I probably used about a 1/2 tank of gas. I'll watch it again next time I'm out, it might've used what it needed to use, just seemed different to me.