Help! motor jumps when accelerating

leeds russ · 10 April 2010, 20:14

Hi all
Hope some one can advice me on the possible problem I have

We have a 3.4m inflatable with an aerodeck with a 9.9 motor on, when we accelerate the engine seems to move backward and forward on the transom, and makes a noise like the propellor is coming out of the water.

I am new to boating and wondered if this is something to expect with an inflatable or do we need to get more weight on the front or the back?

the boat and engine are both new, so presume it is something I am doing wrong rather than the engine being faulty

Hope you can help

Nos4r2 · 10 April 2010, 20:32

How old is it? Are the engine mountings shot?

leeds russ · 10 April 2010, 20:37

The engine is brand new, i tilted the enging so it was as low as it would go in the water
could this make any difference?

The engine seems to run ok it just seems to happend when the boat goes faster

Nos4r2 · 10 April 2010, 21:06

Quote:

Originally Posted by leeds russ

The engine is brand new, i tilted the enging so it was as low as it would go in the water
could this make any difference?

The engine seems to run ok it just seems to happend when the boat goes faster

Yeah, get it so it's parallel to the transom-or possibly one hole out.

astra · 11 April 2010, 09:32

Propeller Cavitation/ventilation with the over rev cutting in,just a thought

biffer · 11 April 2010, 11:06

Quote:

Originally Posted by leeds russ

Hi all
Hope some one can advice me on the possible problem I have

We have a 3.4m inflatable with an aerodeck with a 9.9 motor on, when we accelerate the engine seems to move backward and forward on the transom, and makes a noise like the propellor is coming out of the water.

I am new to boating and wondered if this is something to expect with an inflatable or do we need to get more weight on the front or the back?

the boat and engine are both new, so presume it is something I am doing wrong rather than the engine being faulty

Hope you can help

it might be jumping in and out of gear, ie, not engaging properly

John Kennett · 11 April 2010, 13:34

Quote:

Originally Posted by astra

Propeller Cavitation/ventilation with the over rev cutting in,just a thought

That's my guess.

Russ, is the air floor definitely inflated to the right pressure?

leeds russ · 11 April 2010, 16:12

yes thats a thought
the floor was ok but the compartment below might not have been up to full pressure

Ive only used the boat twice and the first time it didnt do it, and this time i did feel the water pushing the floor up slightly, then when the floor went down and the water released like it made the engine jump

It sounded like the propeller was coming out of the water so we move back but still did it
we tried moving forward in the boat and no change

do you think been slightly under pressure would cause this?/

astra · 11 April 2010, 19:30

I think that this is something inflatables suffer with a fair bit you will have to just try shifting wieght about and trying the engine on different settings,i had same problems with mine but managed to cure it to a degree but sometimes it still does it.

John Kennett · 11 April 2010, 22:37

Quote:

Originally Posted by leeds russ

do you think been slightly under pressure would cause this?

Yes. This type of airdeck is a bit floppy at the best of times, and you really do want to make sure that all the sections are at the right pressure.