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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15048
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Ooh well! Got a 25 hp evinrude outboard motor that does not

Customer Question

Ooh well! Got a 25 hp evinrude outboard motor that does not loss RPM but it loses tork in the water it is like a slipping transmission, the boat still moving but something is going in and out! RPM stay up, propeller is still turning butyou can tell when you are driving it.
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hello my name is ***** ***** am I speaking with?

I don't quite understand you. Are you saying you are loosing thrust from the propeller, is that about right?

Does the boat get up on plane? If not, what kind of speed are you getting from it?

When did this problem start?

Customer: replied 1 year ago.
Hi Jason, yes the boat get up on plane! It does not lose RPM. Its like the propeller is slipping and then ones in a while i get the full engagement.
Expert:  Jason replied 1 year ago.

What is the story on this boat, have you ever seen it work properly? Did you just buy the boat?

Customer: replied 1 year ago.
I own the boat for 3 years, yes it has been running fine until last fall at first i thought it has to do with how many people are in the boat. I am doing research know to narrow it down. Engine fires up and idles great the water pump is working in the low RPMS there is no problem as soon as the boat planes the RPM go up but I am loosing torque in the Water. So i am thinking propeller clutch.
Expert:  Jason replied 1 year ago.

Is the boat falling off plane, or will it stay on plane?

Customer: replied 1 year ago.
it will stay plane but not with maximum speed.
Expert:  Jason replied 1 year ago.

What kind of RPMS are you getting on the tachometer?

Customer: replied 1 year ago.
No tacho, its a 25hp Evinrude on a 14' boat.
Expert:  Jason replied 1 year ago.

So really what you have is a lack of power then, is that accurate?

Customer: replied 1 year ago.
but it is going in and out it is not constant.
Expert:  Jason replied 1 year ago.

Without a tachometer this is really difficult to do. Normally I would ask how many rpms you are dropping.

Expert:  Jason replied 1 year ago.

Does the engine feel like it's dropping a cylinder, or is the drop in more not quite that much?

Customer: replied 1 year ago.
its not quite that much,
Expert:  Jason replied 1 year ago.

If it's not quite that much then chances are there is either a little bit of junk in the carb, or the carbs float is sticking intermittently. Has the carb ever been cleaned/rebuilt that you know of?

Customer: replied 1 year ago.
how is it the carb if the RPM go up and it looses torque?
Expert:  Jason replied 1 year ago.

I asked you "So really what you have is a lack of power then, is that accurate?" And you told me yes

Expert:  Jason replied 1 year ago.

Is your propeller in absolutely mint condition, or does it have any dings on it at all?

Customer: replied 1 year ago.
lack of power but RPM increase! yes its a older motor!
Expert:  Jason replied 1 year ago.

So the prop does have dings on it?

Customer: replied 1 year ago.
the prop has dings on it!
Expert:  Jason replied 1 year ago.

If the prop has dings in it that is going to cause cavitation, and cavitation will make it feel like it is slipping. Are you familiar with the word cavitation, do you know what it means?

Expert:  Jason replied 1 year ago.

Cavitation is when water begins to boils and turn into water vapor around the prop. That vapor is a gas, and the prop gets airbound with this gas. This is why the prop feels like it is slipping, because it is not turning in clean water. Instead what it is doing is turning in a mix of water and water vapor. Cavitation can happen for many different reasons, but the #1 reason is imperfections in the prop. Propellers have to be in near mint condition, or else cavitation can occur. Even very minor defects in the props surface will cause it.

Click this link to read an article about cavitiation, It will go into scientificially what is happening with the propeller

http://www.boattest.com/resources/view_News.aspx?NewsID=3643

The fix for you is going to either get a new propeller, or have yours reconditioned. Does that make sense?

Expert:  Jason replied 1 year ago.

I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you
Jason

Expert:  Jason replied 1 year ago.

Hello, just checking in. No rating has been put through yet. Did you still need help with this issue? The website has already charged you, but they have not credited me yet for helping you out. So I wanted to make sure I got all your questions on the issue answered for you.

Thanks,
Jason

Expert:  Jason replied 1 year ago.

Hello, just checking in. Were you able to get a new prop yet?

Expert:  Jason replied 1 year ago.

Hello, just checking in. The website has charged you but no rating has been put through yet. I wanted to make sure I got all your questions on this issue answered. Did you have any further questions on the issue?

Thanks,
Jason

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