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Volvo ad31p no low end power hard to plane

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Vince Hubach

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" Help! I bought a 1997 Novura

" Help! I bought a 1997 Novurania Equator 600 with a ad31p-a with duo-prop 2.3:1 drive.At per-purchase sea trial the boat would not get up on plane. Motor would only turn 1800 rpm and plow water, no planning. Out of gear(no load)the motor turned 4000rpm. The broker stated to me that the engine was newly rebuilt and only had 1/2hr. since rebuild.I figured this was a prop related problem (solvable) and bought the boat. I took the boat to a reputable Volvo sevice (actualy listed with you) and now $2500+, and hours of talking with Novurania tech. The boat still will not plane.
The dealer did the following:
1. Found props (c-6) to have the hubs spun out causing missalignment among other things. Had props reworked.
2. replaced fuel filters/seperators. replaced air cleaner.
3. While waiting for props to come back they tried a set of b-5's. Boat planed when someone stood in the bow. While on plane they got 4100rpm. and stated it ran like mad.
4. Got c-6's back and the boat performed like original. Could not get above 1800 rpm and No chance of planing.
5. Sent out injection pump for inspection. Stated to me there was some kind of restricter in the pump. Removed restrictor, Reinstalled and sea trialed. Original results. Reinstalled restricter.
6. Tried a-4's. similar to b-5's Planed only when weight was shifted to the bow. Turned way to many rpm's 4200.

As you can imagine I am getting realy frustrated and they are out of answers. I have read your posts extensivly and have read some interesting, "rpm's/props" and "outdrive woes".
I hope you have some suggestions.It seems like the engine develops no low rmp power. Was someting misplaced, or misaligned durring rebuild? Does exhaust pressure setting's come in to play? Is there any kind of other "settings or calibration that was supposed to be done durring rebuild? Any suggestions would be greatly apreciated. I will be checking in frquently as the summer is slipping away. I hope this is not my only option.
Any advice on converting a ad31 to a kad32.Thanks, Vince Hubach "
 
" Vince,

Sounds like you st


" Vince,

Sounds like you still have a prop issue, possible combined with an unfavorable weight distribution.

The 31P does not have a lot of power below 1800-2000 rpm - based on your post I doubt that there is anything wrong with the motor.

Stick with the B5 props for now.

"Boat planed when someone stood in the bow." Is the trim function on the drive unit working properly ? When accelerating the drive should be trimmed in fully. If the boat is equipped with a digital trim gauge it should read -4 trimmed in.

Is the boat equipped with trim planes ? If not; consider installing a set.

Any reason, that you can think of, why the boat would have gotten ?tern-heavy??

Karl "
 
" Thanks for the fast response

" Thanks for the fast response. I believe the outdrive is trimmed ok. It does have trim tabs, and they don't seem to help, maybe too small? I don't think there is any added stern weight. I believe that the engine just has not enough power low rpm. The novurana tech told me they are installing Yanmar 230hp. now. I think this would be the way to go. I was thinking you may have come across this problem before and it was something simple or indicative of this engine. "
 
" Lets back up a little, What

" Lets back up a little, What the weight of this boat overall length and what type of bottom. If they are now putting in 230 Yamamar's that tells me there's a jiant leap in HP?????Del "
 
" normally adad31 use a5 or a6

" normally adad31 use a5 or a6 props,they provide less load while planing unlike the b's........have tried them myself......by the way does anyone know how much the turbos boost??? "
 
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