Intermittent Fault with 115 hp Mercury Blue Band

[Elissa]

I have a 115 hp mercury blue band (not sure of year). At the start of the day it fires easily but on takeoff it gets to 1800rpm and will not go further. The engines sounds like it is struggling. I put it back into neutral and try again and keep doing this a number of times and then all of a sudden it just takes off (make sure you are hanging on!)and will not do it again for the rest of the day. It only happens first thing in the morning and not every morning either. I have had it checked out by mechanics and they cannot find the problem. Has anyone experienced this problem before. The motor runs exceptionally well except for this problem.

 

[Laddies]

Re: Intermittent Fault with 115 hp Mercury Blue Band

Does the engine have a dist, or ADI ignition system

 

[MercFan]

Re: Intermittent Fault with 115 hp Mercury Blue Band

My guess would be over priming or bad needles and seats? When you prime it first thing, do you have fuel dripping from the carbs?<br /><br />I'm currently struggling with a similar problem and I hope I have it licked now. Will only know by the week end though. While your engine is struggling, feel your primer bulb. It should be stiff or just half a pump from stiff. Your performance should not increase when you pump it. And the bulb must expand easily after pumping it.

 

[Elissa]

Re: Intermittent Fault with 115 hp Mercury Blue Band

The engine has an ADI ignition system.<br />The engine starts first time and we uaually drive a short distance before I put it under load. The problem occurs when we try and get the boat on the plane and we put the motor under load. It struggles and does not go past 1800rpm. Once it does take-off the problem will not occurr again till the next day. Could it be a carb problem associated with the choke? The auto choke appears to operating OK.

 

[Clams Canino]

Re: Intermittent Fault with 115 hp Mercury Blue Band

Make sure the prop pitch lets it get well over 5000 at WOT. Past that suspect the idle needles 1st.<br /><br />-W

 

[Laddies]

Re: Intermittent Fault with 115 hp Mercury Blue Band

The chances are it's a fuel related problem and the carbs and fuel pump need to be rebuilt, but sometimes a switchbox failure will act the same way so after the engine acts up ck it for spark, if you have lost fire on 3cyl. then it's a box or one side of the stator and if it loses spark on 2 cyls, it's a trigger

 

[rodbolt]

Re: Intermittent Fault with 115 hp Mercury Blue Band

what laddies said, but my experience is if it only does it after prolonged idle the fuel pump is going bad and allowing a low fuel level condition in the bowls at low speeds. at higher speeds the weak diaphram can keep up.<br /> usually if a needle is leaking it wont idle long before it floods and dies.

 

[Boatwizard]

Re: Intermittent Fault with 115 hp Mercury Blue Band

This is an easy one!!! It only does it once when cold and never the rest of the day and not every time?<br />Your trigger is not moving (advancing) because the grease has got it stuck. After the throttle is held down and or it warms up, it turns loose all at once and takes off like a rocket. Take the flywheel off and use some contact cleaner and clean out the old grease and lightly (LIGHTLY!) lube it again. <br />To check it, take the covers off and advance the throttle with engine cold and not running. Look at the timing arm and see if it's moving. It should be stuck and when you touch it the spring will advance it.

 

[Elissa]

Re: Intermittent Fault with 115 hp Mercury Blue Band

Thanks Boatwizard I will try it and let you know of the outcome.

 

[Elissa]

Re: Intermittent Fault with 115 hp Mercury Blue Band

Problem is now getting worse! It now occurs every time the motor is started at the start of the day and it takes longer before it takes off! Once it has taken off it never misses a beat. Fantastic motor.

 

[ortz]

Re: Intermittent Fault with 115 hp Mercury Blue Band

Problem is now getting worse! It now occurs every time the motor is started at the start of the day and it takes longer before it takes off! Once it has taken off it never misses a beat. Fantastic motor.

have someone bend the harness where it curves up to the motor while u r driveing,if u have a broken wire in there it should show up. Don't be standing up ..lol. If it cuts out it could cut in again. HAD THAT HAPPEN. Stay closer to shore or have some tools with u to make a splice. Make sure to disconnect battery while repairing. If u suspect thats what it is, cut the sheath and feel the wires, it could be broken in the insulation and u would not see it. good luck....Ortz