Outboard Motor issues

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Outboard Motor issues

Postby lablover0929 » Tue Dec 20, 2011 7:18 pm

I have a 1986 Mercury 50hp tiller on a aluminum Duracraft 1860. The motor sounds great on the muffs. But under a load, its a dog. It's barely doing 10mph.

We have checked the compression with all cylinders hitting at 125. Spark test came back all sparking. Took the carbs off and did a cleaning, very little varnish if any at all. Blew out all the jets, and put back together. Fuel sample did not show anything water, or trash. So, we started looking at the prop. The motor had 10 x 15pitch 3 blade on it when I bought the motor and boat. So, they had me put on a 10 x 13 pitch. The boat doubled its speed, and almost planed out. Had a little bit of hesitation at WOT, but it was finally stretching its legs.

So, they ordered me a 12.1 x 9 pitch prop, said it would make this rig sing! Got it put on Friday, ran it saturday morning, and its worse than the original!!!! At WOT it wants to bog down. I am at my breaking point now. Went back to the dealer/mechanic, and he said its in the motor, just bring it in. He said the 9 pitch should have jumped it out of the water, and humming. May even have to back off the throttle even.

Went by two other repair places today, stated everything above. One said to go with a 10.25" x 14pitch prop, and the other said to go with a 10.50-11" x 11pitch prop. Both said the 9 pitch prop was a waste, and that a prop like that is for pontoon style boats.

Where do I go from here?????? :help: :mad: :huh:
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Re: Outboard Motor issues

Postby big_country » Tue Dec 20, 2011 7:28 pm

Short tail. Then you dont have to worry about the muffs.
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Re: Outboard Motor issues

Postby lablover0929 » Tue Dec 20, 2011 7:48 pm

big_country wrote:Short tail. Then you dont have to worry about the muffs.


Thanks for your thoughtful words......

If you don't have any useful ideas, hit the back button and troll on over to another thread. My patiense is thin, and your childish remarks are not needed.
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Re: Outboard Motor issues

Postby waterfowlmagnet » Tue Dec 20, 2011 8:06 pm

Is fuel from the tank flowing good? A good indicator would be the bulb sucking in, often caused by the vent on the lid closed or trash.
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Re: Outboard Motor issues

Postby lablover0929 » Tue Dec 20, 2011 8:41 pm

waterfowlmagnet wrote:Is fuel from the tank flowing good? A good indicator would be the bulb sucking in, often caused by the vent on the lid closed or trash.


The bulb is keeping its shape and staying firm. I keep the lid a little loose to allow it to vent.
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Re: Outboard Motor issues

Postby waterfowlmagnet » Tue Dec 20, 2011 9:09 pm

lablover0929 wrote:
waterfowlmagnet wrote:Is fuel from the tank flowing good? A good indicator would be the bulb sucking in, often caused by the vent on the lid closed or trash.


The bulb is keeping its shape and staying firm. I keep the lid a little loose to allow it to vent.



Check the fuel pump, the problem seems to be in the fuel system somewhere. I'd trace out the fuel system from the quick connect to the carbs and check flow
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Re: Outboard Motor issues

Postby waterfowlmagnet » Tue Dec 20, 2011 9:12 pm

Those old pumps won't take the ethanol in fuel these days. but you can get one that will cheap if that's what it is
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Re: Outboard Motor issues

Postby duckslaya_187 » Wed Dec 21, 2011 5:36 am

Stay with the 11 pitch prop. A heavy boat with that size motor needs a large diameter and relatively small pitch prop. Just not a 9 pitch. DO NOT use that 14 pitch prop with a duck season type load. If you fish this boat in the summer you could get away with that 14, but not under a big load.

Number 2. You say you took the carb apart, but have you actually soaked and rebuilt it? Could be a weak fuel pump but a pressure test will tell you that. (Need 5 to 7 psi). Also check all your fuel lines for cracking or even at the age of engine and new ethanol and reformulated gases you might have some entire corrosion and failing resulting in a blocked line. Consider replacing all of the internal lines.
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Re: Outboard Motor issues

Postby lablover0929 » Wed Dec 21, 2011 6:48 am

My stepdad and i did the carbs. He is a retired NHRA driver, and has been around motors for many years.
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Re: Outboard Motor issues

Postby duckslaya_187 » Wed Dec 21, 2011 7:00 am

No one is questioning your step dads credentials so why are you getting defensive, really though if we want to nit pick as a driver his job was to drive not rebuild motors, but you never answered the question. Did you soak the parts to allow for accumulated varnish and/or other obstructions to be loosened and then properly cleaned?
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Re: Outboard Motor issues

Postby FOWLER2671 » Wed Dec 21, 2011 7:44 am

It may not be part of the problem but it wouldnt' hurt to add a spin on water seperating fuel filter. My motor is only eight years old but Ive' had issues with moisture in the fuel as well.
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Re: Outboard Motor issues

Postby lablover0929 » Wed Dec 21, 2011 9:43 am

I dont think i was being defensive at all. Sorry if you felt that way. The bowls did not have any build up, varnish or trash. They were wiped and cleaned with new carb cleaner. All jets were taken out checked and blown clean. All fuel lines are fairly new.
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Re: Outboard Motor issues

Postby duckslaya_187 » Wed Dec 21, 2011 9:56 am

Any idea on fuel pump pressure?

Do you have a tac?
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Re: Outboard Motor issues

Postby Rob DeHaven » Wed Dec 21, 2011 12:58 pm

could be carbon build up in the exhaust ports not letting all the exhaust flow out so the air /fuel can flow in. had a motor with this problem once and had the same symptoms as yours. just a thought since it seems you have checked other issues.
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Re: Outboard Motor issues

Postby lablover0929 » Wed Dec 21, 2011 2:20 pm

Rob DeHaven wrote:could be carbon build up in the exhaust ports not letting all the exhaust flow out so the air /fuel can flow in. had a motor with this problem once and had the same symptoms as yours. just a thought since it seems you have checked other issues.

What might be the remedy for this? It may not be it, but it wouldnt hurt either.
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Re: Outboard Motor issues

Postby dablaw » Wed Dec 21, 2011 3:27 pm

Couple of things come to mind here..Dump your fuel first and foremost into a clean white 5 gallon bucket..Check for trash and any specs of dirt..Check both fuel connections(Fuel tank and motor)for even the tiniest leak when you really pump the bulb hard..Also check fuel line the same way(especially around your hose clamps)...Make sure you have a vented gas cap...I know all this sounds too simple, but the tiniest of air/fuel leaks, and the tiniest bit of water ot dirt can play hell with these motors in particular...
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Re: Outboard Motor issues

Postby lablover0929 » Thu Dec 22, 2011 6:19 am

Went last night and traded props. Got a 11.6 x 11" due to that was all he had at the time. Dumped all fuel out of tank, getting a fresh tank today. Going to mix some seafoam into the concoction ad well. Going to get a timimg light from a friend and test the timing as well. May even change out fuel pumps.
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Re: Outboard Motor issues

Postby duckslaya_187 » Sun Dec 25, 2011 3:56 pm

Where you at with this thing?

Might I make another suggestion? Keep the prop you have until you get the WOT throttle issues worked out. Then if you do not have a tac get one (tiny tach makes a great unit for under $50). To properly prop, no pun intended, your boat you need to know what RPM you are spinning at WOT under the typical weight load.
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Re: Outboard Motor issues

Postby mike_b » Tue Dec 27, 2011 8:57 pm

As for the prop, an all season prop will be around 10 inch, 13 pitch for you. But my mechanic says I should base it on my WOT RPMs. I have a small tinytach on my motor, but you can run it WOT and read your RPM, they should be around the MAX RPM for your motor with your normal load on your boat. So that load may change during duck season, but honestly, I'm never running WOT at 4AM.

In general, I'd say your prop is not causing it to bog down. If by what you mean "bog down" is the engine runs slow. Reducing the pitch should INCREASE your RPM. A 9 pitch should have much less acceleration than a 13 pitch, but more top speed, in theory. It probably doesn't have enough torque to get the boat on plane. 9 is just too low for an 1860 jon or mod-v jon. I'd pick a prop 11-15 pitch.

I agree with others... I'd try new fuel first of all, check lines, verify your fuel-oil mix. What type of pump do you have? Try pumping the primer bulb as you accelerate. Keep pressure on it. If that helps, your pump is weak.

lablover0929 wrote:What might be the remedy for this? It may not be it, but it wouldnt hurt either.


Try Seafoam. I normally run it in my mix, along with marine stabilizer. You can run it a bit heavy at first to help clean out carbon buildup. But for normal use, you don't use much.

Good luck.
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Re: Outboard Motor issues

Postby mike_b » Tue Dec 27, 2011 9:05 pm

lablover0929 wrote:Went last night and traded props. Got a 11.6 x 11" due to that was all he had at the time. Dumped all fuel out of tank, getting a fresh tank today. Going to mix some seafoam into the concoction ad well. Going to get a timing light from a friend and test the timing as well. May even change out fuel pumps.


Screwing with timing can be an ordeal. To properly set it, you normally need a specially weighted "prop" usually only dealer mechanics have these and to run it in a tank. If you get a Clymer's book for your motor, it might have a good section on resetting the throttle and spark advance linkages. Mine did for my ruddy. Then from there, you can adjust as needed to get your idling running correctly, etc.
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