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ethan

my outboard motor is lagging

33 posts in this topic

My outboard motor is not working out as it should. Water wasn't coming out from the pee hole, so we took it out to the this one guy to fix. He put in a new impeller and now water comes out. But the motor is really lagging. I can't put it in full throttle, and if I do, the motor will sound really loud but the propeller isn't spinning. Does anyone know what the problem is? Is it because the guy who installed it did something wrong? Thanks.

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forgot to put the shear pin in(older motor), or you have a spun hub.. its a prop problem.. unless im overlooking something here half asleep.

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It helps a lot knowing which motor is it. Year, make, hp etc.

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Does it move at all? If so it would most likely be a spun prop hub or shear pin thats got enough of a burr to work under low speeds but spins are higher speeds.

If it doesn't move at all its possible the shift linkage didn't get put back together. Whats the year and hp of the outboard.

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Hey thanks for getting back. So I'm not so sure of what you're really talking about. I dont know too much about boats and motors. This is really my first one. Where is the shear pin? And what is the spun hub? Sorry! Thanks.

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the year of the motor I'm not so sure I think its somewhere between 1960 to 1970. It's a 18hp Evinrude. thanks.

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Go to the propeller and take the cotter pin out of the prop nut.

Take the the prop nut off. Slid the prop off the shaft. You should have a shear pin that goes through the prop shaft and if you look at the back side of the prop you'll see an indentation where that shear pin sets into. The shear pin may be broken and thats your problem. Get a replacement at any dealer/shop or prop repair shop. Its possible that the shear pin is intact but your prop nut isn't tight enough. All it should do is make contact with the prop, if its too loose and theres enough slop the prop could back out enough to were its not seated onto the shear pin.

A shear pin is just that. When you hit something the shear pin will break. This takes the brunt of the force instead of your prop and prop shaft.

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hey thanks a lot for getting back. I'll try that today when I get home. That does sound like the problem and it does make sense when you think about it.

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It's good to have extra shear pins in your tackle box, too.

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Ya spares are good to have. grin.gif I've been know to cut the head off a nail before when in a pinch.

Look at above the bracket where your outboard clamps are. There might be a rubber grommet with a couple spare shear pins and a cotter pin.

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so do you think I should try cutting a nail that's the right size and put it in place of the pin? I mean it should work if the nail is the right size do you think?

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Its ok for an emergency fix, but shear pins are made of brass so they break easier in case you hit something solid, and they dont rust.

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so what if the pin is still in good shape? I took it apart yesterday after work, well it seems to be in good shape! Other then the pin, what else would be wrong with it? I dont think it's the motor itself. I mean it starts up good and when in full throttle the motor rev's up like it has power to it! Anyone with any suggestions?

Thanks.

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Was the prop nut snugged up? In reference to my earlier post, if its nut up against the prop the prop could drop back far enough to where its no longer in contact with the shear pin.

Put the prop back on and turn the prop till its grooves line up with the shear pin. When you get to that point the prop will pop forward a 1/4" and when you turn the prop with the outboard in gear you'll feel resistance, enough resistance to were you can't turn the prop any longer.

Now put the nut on and snug it up to the prop.

While your at it drain the gear oil in the lower unit.

You'll see a are flat slotted screw down low and one up high. Not the smaller Phillips head screw! Remove the lower screw then remove the upper screw. Tell me what comes out. Look for metal, water, gear oil with water beaten into it or nothing.

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Use ST's advice here.. he knows motors in and out.. I'm trying to think up other scenerio's that may be causing this... and a couple came to mind...

You dont have a short shaft motor on a long shaft transom(20" transom).. if the shaft is too short, the prop will come out of the water once you reach a certain speed.. hence causing the effect of a loss of power. If you have cavatation on the bottom of your boat, it can cause the same effect.

Another thing it might be if you are getting a bunch of noise, but still have power at high speeds... your exaust port might be coming out of the water at higher speeds.. the exaust above the water makes a heck of a lot more noise then when its under.

If your motor comes out of gear, it will usually give a good jerk, or jump when it pops out, and the motor will rev very fast if its at full throttle immediately... it is usually noticable if a motor jumps out of gear. If this is the case, the linkage needs to be tinkered with.

My guess is your prop is coming partially out of the water for some reason.. did you have this motor on your boat in the past?

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fisher dave,

your scenerio's are so onto the problems I'm having! It's almost like you're in the boat with me. Anyway, I can't really talk in outboard motor terms so hang in here with me. Cavatation on the bottom of the boat? I'm not sure what you're talking about. the linkage, is that the two screws where the forward and backward is connected? How can I tell if its a short shaft? this is the first time the motor has been on the boat. I'll be going at maybe half throttle and it'll keep going, but once I try to go faster the motor just rev's very high and you can see that the lower unit comes out of the water! I dont think it jumps out of gear cause I dont hear anything loud or any jerks. Thanks for the helpful info.

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ST,

I think yesterday it was kind of gear oil and a little of water mixed together. It seemed kind of milky also. I dont think there's in metal in there thought. The guy that put in the new impeller for me did change some gear's and said that maybe it was getting old. Well after that, the problem started. I took out the gear and took a close look at it, but it didnt seem to be too bad. Now will old oil gear oil effect the gears? I'm putting new oil in today after work. I'll try running it today and see how it runs and come back and update you guys. Thanks for all the info given here.

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Yea it affects the gears. I go alot so I change mine 2 times a year. When it gets that milky color then its definately time to change. I had a problem a couple years ago when we had just got our last fish and going to head to the dock, when I switched gears to forward. The motor still ran but the propeller didnt spin, so we had to get help to get off of the lake. I took it to a repair shop and they said the prop was shot so I had to get a new one.

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Quote:

once I try to go faster the motor just rev's very high and you can see that the lower unit comes out of the water!


This sounds alarming to me. I think you're cavitating (too much air; not enough water around the propeller)

Does your motor have a shallow water drive (tilt setting between all the way down, and all the way up)?

Do you have the motor mounted so the motor mount brackets are completely lowered onto on the transom and not slightly higher?

Is there anything mounted on the back of this boat?

You said this is the first time this motor has ever been on the back of this boat...

Does the front of the boat stand up pretty high in the air when you're throttling up?

How large of a boat are we trying to power?

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Fisher Dave may have solved this one. With the outboard on the boat look at the cavitation plate.(horizontal fin above the prop) It should be the same height as the bottom of the boat. If its 5" above the bottom of the boat you have a short shaft(15") outboard on a boat with a 20"(long shaft) transom and theres your problem.

Typical there are two lengths shafts used and two transom heights. They would be 15" (short shaft) and 20" (long shaft).

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I do have the motor at it's lowest. There is however nothing mounted on the back of the boat. The boat does stand up sometimes if it catchs speed. The boat is I think 14 feet, the motor isn't really all that big. Its a 18hp if you know how big that is. Thanks a lot for getting back. I have no clue to what the problem is here!

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I havent checked to see where the propeller stands, but I think it might be just a little lower then the boat. I came to another problem last night testing it out. Its seems like at lower throttle the motor almost wants to shut off. At lower throttle the pee hole would spit out water then some smoke making the motor sound like it's going to die! It'll keep on doing so until I rev it up more. Another funny thing is that everytime the motor first starts going it'll go really fast like it suppose to. I mean the motor only goes fast that very first time I put the boat into the water and start going. But after that on the lake I'll never get the boat to go as fast as the first time in the water.???? It almost seems like thats the only time that the motor is cool enough for it to go that fast,but after it warms up it wont go to full throttle.... If you have any other ideas please write back with some. I'm pretty new at this so I have no idea whats going wrong! Thanks for all your replies.

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Sounds like other symptoms you're trying to relate to the no water problem. Maybe it's another problem. Can you rev it up to high RPM's in neutral? Venting of the gas tank ok? Fuel mixed properly? Spark plugs new?

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ethan..

as S.T. said.. take a look at the lower unit of your motor. The cavatation plate is the horizontal (level area) plate directly above your prop... you sometimes may see *wings* (hydrofoils) mounted on them on other motors.

That cavatation plate should be even, or possibly lower than the bottom of your boat. If that plate is at least as low as the bottom of your boat, you are fine on shaft length.. it doesnt matter if its 2, or 200 horse power.. It must be the proper length shaft.

14' boats come in both 15"(short), and 20"(long) transoms.

Are you by chance in, or near the metro area?

I am almost positive the problem you are facing is you have a short shaft motor on a long shaft transom.

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Ethan, I went back to the beginning of this thread. First you say the prop isn't spinning and now you say it is but it cavitates? You said the impeller was replaced and pumping good, now you say it isn't pumping good. Your feeding us bits of conflicting info here. Are you pulling our leg?

If we could see and sit in the boat while this is happening we'd have you good to go in no time. You have to answer the questions asked or theres no sense in asking if your not going to answer.

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