Can a prop bog down your motor?

[Skytex83]

I've got an 82 evinrude 70hp outboard that keeps dying when you put it in the water and try to accelerate. It will go into gear just fine and idle/move a bit faster than idle and the engine runs great. Using water ears on it at home, the engine runs like a champ. However, putting it in the lake, anything past say 1/4 throttle will bog the motor down and kill it. A marine mechanic friend said it could be my prop. I just got the boat and had a shop check everything out and make sure it ran good. However I was miffed to find it didn't run after going in. So, I took it back to them and he called and left a message today saying he replaced the prop and it runs good now. I'm totally lost. The only thing I could guess is too large of a prop was put on by the previous owner and it was digging the water too hard? Can someone enlighten me as to how changing a prop could make the boat run? I assumed it was a carburetor problem or maybe a fuel pump.

 

[Maclin]

Re: Can a prop bog down your motor?

Need more details to be able to help. What boat is this on? Is the boat new to you? Did it always run like you described? What pitch prop did he remove? What pitch prop did he put back on?

You have not run it yet I take it, so be optimistic but verify results yourself.

 

[Maclin]

Re: Can a prop bog down your motor?

Sorry, I did not answer the question, so..... Yes if the pitch is way too high for the boat/motor combo.

 

[Texasmark]

Re: Can a prop bog down your motor?

Question: Can a prop bog down your motor? Answer: You bet your bippie, in a New York minute.

Mark

 

[Skytex83]

Re: Can a prop bog down your motor?

got the boat back. too windy to try it out. He said the prop was for a 115hp when mine is only a 70hp. the numbers off the old one are 13x19. I'd have to take the prop off to see what the one he replaced it with is. Also said the carbs were running lean so he richened them up. Hoping the weather backs off enough to let me take her out this weekend and see.

 

[jestor68]

Re: Can a prop bog down your motor?

. Also said the carbs were running lean so he richened them up.

There's your answer. It's a fuel delivery issue and has nothing to do with a 19 pitch prop.

It likely won't show up running on muffs, because there's no load on the motor. You can check it with the boat on the trailer(save yourself some time). Just back it in enough to put the stern in the water and start the motor, put it in gear and give it some throttle and see if it wants to stall out.

If the idle circuit is set too lean, the motor will stubble (or stall out) when you first advance the throttle because it is still running on the idle circuit initially until it transitions to the high speed circuit. That's why the idle adjustment should be done in the water(or in a test tank), in gear so there's a load on the motor.

The tech should know how to verify that the timing advance is adjusted properly, as that could also cause the motor to stubble/stall if the timing advance is not synchronized properly with the throttle movement.

 

[Maclin]

Re: Can a prop bog down your motor?

Still not sure what kind of boat this engine is on or how long you have owned or run it, but in my opinion a 19p for a 70hp engine does seem a little tall and could have been a contributor to your problem.

 

[BonairII]

Re: Can a prop bog down your motor?

Still not sure what kind of boat this engine is on or how long you have owned or run it, but in my opinion a 19p for a 70hp engine does seem a little tall and could have been a contributor to your problem.

I'm running a 17p(@5900 RPM) on my older 75hp....and could run a 19p no problem.

A very large pitch increase will bog a motor down, but in this case I suspect an ignition and/or fuel delivery problem rather than a prop issue.

 

[Maclin]

Re: Can a prop bog down your motor?

Still do not know the boat it is, length, fiberglas or Aluminum, if it always acted like that, etc...all factors to consider. My posts were dealing with the questions about if the mechanic's diagnosis sounded right. Now we know the mech found engine issues also, so I bet the OP is good to go now. I like to get all the facts/factors out in the open so future searchers can make better decisions about if this applies to them or not.

 

[81_chapparel194]

Re: Can a prop bog down your motor?

I've got an 82 evinrude 70hp outboard that keeps dying when you put it in the water and try to accelerate. It will go into gear just fine and idle/move a bit faster than idle and the engine runs great. Using water ears on it at home, the engine runs like a champ. However, putting it in the lake, anything past say 1/4 throttle will bog the motor down and kill it. A marine mechanic friend said it could be my prop. I just got the boat and had a shop check everything out and make sure it ran good. However I was miffed to find it didn't run after going in. So, I took it back to them and he called and left a message today saying he replaced the prop and it runs good now. I'm totally lost. The only thing I could guess is too large of a prop was put on by the previous owner and it was digging the water too hard? Can someone enlighten me as to how changing a prop could make the boat run? I assumed it was a carburetor problem or maybe a fuel pump.

please advise what you do to correct the problem. i have the same exact issue on a 81 evinrude 90hp. i see your mechanice richened the fuel. please advise how this was done and if it fixed your problem. i do have a smaller prop i can try on mine if that really was your problem. keep us updated

 

[Skytex83]

Re: Can a prop bog down your motor?

Ok backed the boat into the ramp today and yes it's fixed.

For those asking, the boat is an aluminum 16ft bass tracker 3 1984 model with an '82 70hp evinrude 3 cylinder. I've owned the boat now a total of 2 months. When I purchased it, the motor ran fine, again on ears, but when put in the water, bogged down. Took boat to mechanic once and he replaced a bad fuel line and changed the lower unit oil, boat still had same problem leading to my op.

Like I said, I'd have to remove the prop to get a look at the size he replaced, but the one that came on it was a 13x19 and had atleast one blade bent a bit out of shape and a good sized chip taken out. As for RPM's, I have no clue. The boat doesn't have a tach. Yes he also richened the carbs. I couldn't tell you how as I've never done it and would only have a basic knowledge from doing lawnmower carbs.