black max slow to take off

[jigmister1]

1987 175hp black max on a bass boat.

it runs like a bat out of hell. never let me down yet.

problem

at blast off it hesitates before it takes off. push throttle wide open and it take a few seconds before it catches. I think that to be normal?

however, every once in a while boat is idling I give it throtle to blast off and nothing happens. give it more until it its pinned wide upon. its not enough to even get on plane. after a few minutes of doing this it catches and runs perfecly.

it dose this every 5 or 6 trips out and normaly only if the boat has not been used in 2 weeks or more.
any idea???? been a while since I changed the fuel filter. could that be it?

thanks

 

[CharlieB]

Re: black max slow to take off

Since two strokes do not have an accelerator pump the idle mixture is set RICHER than best idle speed to allow that extra fuel for crisp acceleration.

When a motor begins to hesitate, or bog, on throttle opening, you can count on the carbs needing a good cleaning to restore proper fuel flow.

Be glad you have noticed, if this were a restricted main you would have melted a piston.

 

[jigmister1]

Re: black max slow to take off

how difficult are they to clean? can I try some carb cleaner without pulling them off the engine?

think a dirty fuel filter can cause the same problem?

really can not afford to pay a mechanic right now. Its been tough for me to find a conifident mechanic. Bad experinces really keep me from wanting to spend alot of money to have my stuff come back worse off.

 

[Dave1027]

Re: black max slow to take off

Why don't you first try opening up the idle mixture screws a 1/4 turn each. See if that helps. Maybe 1/2 turn?

 

[j_martin]

Re: black max slow to take off

how difficult are they to clean? can I try some carb cleaner without pulling them off the engine?

think a dirty fuel filter can cause the same problem?

really can not afford to pay a mechanic right now. Its been tough for me to find a conifident mechanic. Bad experinces really keep me from wanting to spend alot of money to have my stuff come back worse off.

You cannot do any carb cleaning that would be useful without taking them off the engine. Besides that, carb cleaner would be really hard on the rest of the engine. The carbs are not hard to pull off, and they are not hard to work on. Kits are 20 bucks or so. Floats, needle, and seats are probably OK. I'm guessing you have WH(nn) carbs on it, and they do not have idle adjust screws.

A dirty fuel filter is most likely to manifest at WOT, or the hole shot might go good for 2 seconds, then die.

At first glance, these V6 mercs are intimidating, but when you get into them, they really aren't very complicated. If you take the shoot first and ask questions later approach to troubleshooting, they will break the bank in short order. Logical, systematic diagnostics is the key to an economical and effective repair.

A few questions are in order to set the stage.
When did this problem manifest? (Always there, suddenly, slowly)
Does it idle smoothly? (relative with merc v6's, I know)
Does the idle get rough in time? Is it missing at idle, loading up some cylinders with fuel?

Understand, the problem could be either fuel or electrical.

hope it helps
john

 

[jigmister1]

Re: black max slow to take off

the problem is very intermittent. It only happened twice now in about 10 fishing trips. Each time only once. once on plane and running its good for the rest of the day and good on the next number of trips out.

the idle is smooth.

Always been stubborn to start up cold if shes not been run in 5 days or more.
back to back days and she fires up at first bump of the key in the morning.

The problem with the hesitation out of the hole comes after shes not been run for a week or more.

 

[jigmister1]

Re: black max slow to take off

carbs do not really scar me. I have rebuilt a few automotive carbs with good luck. Being marine and the fact there is three of them that must be syncronized is what bothers me some.

If I carfuly remove them and replace them back exacly the way the come out should I end up close to where it needs to be or is adjustment somthing I need to learn on these guys?

 

[duhn]

Re: black max slow to take off

If you have rebuilt an automotive carb with sucess, then these merc carbs should be a breeze. Get the manual and follow instructions. If you are mechanically inclined you should be able to do it.

 

[jigmister1]

Re: black max slow to take off

talked with the local merc mechanic today. He said it sounds like a dead spot in the stator or a switch box. When I asked about the carbs he said if it were a carb issue he would suspect the problem to be constant

 

[j_martin]

Re: black max slow to take off

talked with the local merc mechanic today. He said it sounds like a dead spot in the stator or a switch box. When I asked about the carbs he said if it were a carb issue he would suspect the problem to be constant

Stators don't have dead spots. Not real likely to be a switchbox unless you can pin it down to a temperature issue. You have given me a clue, however.

Is it smokey when it's acting up?

Check the alignment of the VRO arm. It might be getting too much oil at idle. Takes awhile to warm up. If the linkage falls off, it fails rich.

If it's smokey when you start it up after days, could be a similar problem, only this time it would be a faulty check valve in the oiler system, starboard side, low and forward.

hope it helps
John

 

[jigmister1]

Re: black max slow to take off

well it is smokey at start up thats for sure. I am not sure if it is any less or more smokey when it was acting up far as hesitation. I changed the check valve a year or 2 ago because the oil tank was pressurized even if I had not run the boat in weeks. that cut down on alot of the start up smoke. the smoke seems to be increasing latley. at fisrt start of the day its pretty bad. then after I run her to a spot, shut off and fish for a while the smoke is much much less on next start up.

 

[j_martin]

Re: black max slow to take off

well it is smokey at start up thats for sure. I am not sure if it is any less or more smokey when it was acting up far as hesitation. I changed the check valve a year or 2 ago because the oil tank was pressurized even if I had not run the boat in weeks. that cut down on alot of the start up smoke. the smoke seems to be increasing latley. at fisrt start of the day its pretty bad. then after I run her to a spot, shut off and fish for a while the smoke is much much less on next start up.

Check the check valve, and also the linkage adjustment on the VRO. I'd be willing to bet that if you let it sit for a week, then pumped up the primer ball and then pulled a main jet, you'd get a handful of mostly oil. Shouldn't do that.

hope it helps
john

 

[jigmister1]

Re: black max slow to take off

is there a way I can temparley disable the oil system and mix it in the tank like the old days?
I am thinking of running it that way for a while. If all the problems go away I would have eliminate alot of possibilities

 

[jeffersondodson561]

Re: black max slow to take off

is there a way I can temparley disable the oil system and mix it in the tank like the old days?
I am thinking of running it that way for a while. If all the problems go away I would have eliminate alot of possibilities

You can, but I would not mess with it. Mercs oil injection system is good. If you decide to clean the carbs just remember your sync and link is the most important, all throttle plates should open at the same time and at wide open throttle throttle plates should be "perfectly horizontal". And don't overlook checking timing. Outboard two stroke carbs are easy and somewhat forgiving but they are just carbs, so I wouldn't worry about it. And it is not uncommon for oil tanks to hold pressure.

 

[jigmister1]

Re: black max slow to take off

ok so all the carbs open and close at the same time.

so if carb 1 is at 50% 2 and 3 are at 50%. thier orentation is the same through out the entire range of 0-100 0 being idle 100 being WOT

do I undertand this correct?

 

[j_martin]

Re: black max slow to take off

I think we've been powned again.