nissan 25hp not performing as expected

[teakman]

I recently bought a 2000 Nissan 25hp 2 stroke from our local dealer, he claims he took the 'throat plate off' to make this motor a 30hp. I've put it on a 14' true inflatable, not a rigid inflatable. I've got a console and some seats in it to add a bit a weight (125 lbs), too.

Problem is :

1) The boat is a dog !!! It will plane, but only does about 15 mph ... maybe 18 ! That is not fast enough. Something must be wrong with this engine right ? Or maybe the non-rigid hull is really grabbing the water and not allowing me more speed ? 4 adults in the boat, no plane at all !

2) Can it really be a 30hp by just taking out the 'throat plate' as the dealer claims ? Or is there more to it ?

Suggestions ?

 

[TOHATSU GURU]

Re: nissan 25hp not performing as expected

Yes, something is wrong somewhere and CHANGING the flange gasket and timing will make the 25 into the 30. Take it to another dealer.

 

[teakman]

Re: nissan 25hp not performing as expected

Thanks Guru ... glad someone agrees its the engine and not the boat.

Can you be specific about changing the timing, do you know what to change it to ? Also, what compression would you suggest ? I have a mechanic coming by tonight to check it out.

 

[TOHATSU GURU]

Re: nissan 25hp not performing as expected

You cannot change compression and the timing can be found in your service manual.

 

[teakman]

Re: nissan 25hp not performing as expected

Ha, I'm not that much of a newbie, I know you can't change the compression I meant what compression reading should I come up with ? I'm gathering around 125 ?

You're right though, I need the manual ASAP. Off to buy it tomorrow.

Now today the engine is bogging under load at anything but idle, intermittently too which is bizarre, kind of jumps from high RPM to low and back again at full throttle. I'm soaking the carb tonight and will let you know.

 

[TOHATSU GURU]

Re: nissan 25hp not performing as expected

Your looking for the compression to be even rather than a number.