Replacing AQ175 to 225D

[mrwad]

Hello everyone,

I have 7,5 m long and 2,5 m wide day cruiser boat that weights about 1800 kgs. The engine is running ok at the moment, but it seems that it would need a big service pretty soon. I have found just fully serviced Volvo Penta 225D, GM 305 (about 230 hp). At the moment I have Volvo Penta AQ175 (about 175 hp) with Volvo Penta 280 stern drive. I think they should fit perfectly just straight forward as the 225D had the same stern drive. At the moment I am doing about 50-50 km/h on 6000 rpm. Would there be a big gasoline consumption difference for my boat? Do I have to change the impeller on my stern drive? Any other things to keep in mind changing these two?

Thank you!

 

[captmello]

The swap would be easy, as you say, going from the 4.3 V6 to the V8. Volvo used different gear ratios in the lower units of the outdrives for different size motors, but you may get away with the V6 gearing since your not looking for high performance.

If you're really running at 6000 RPM, your motor is going to fail soon! you should be around 4500 rpm max, same goes for the 225D.

Your impeller is in an engine mounted pump, not in the sterndrive.

Gas consumption should be similar.

 

[mrwad]

The swap would be easy, as you say, going from the 4.3 V6 to the V8. Volvo used different gear ratios in the lower units of the outdrives for different size motors, but you may get away with the V6 gearing since your not looking for high performance.

If you're really running at 6000 RPM, your motor is going to fail soon! you should be around 4500 rpm max, same goes for the 225D.

Your impeller is in an engine mounted pump, not in the sterndrive.

Gas consumption should be similar.

Thank you for the answer and sorry for my English, I meant propeller not impeller. I would also like to rise performance with V8 as the boat would probably go a little bit faster or achieve the same speed at lower RPM? Also last summer I had problems with spark plugs. While leaving the port or using on high RPM (no matter low or high) one of the 6 spark plugs failed and I had to stop and change the failed one. That happen probably 4 times last year.

 

[Bondo]

Thank you for the answer and sorry for my English, I meant propeller not impeller. I would also like to rise performance with V8 as the boat would probably go a little bit faster or achieve the same speed at lower RPM? Also last summer I had problems with spark plugs. While leaving the port or using on high RPM (no matter low or high) one of the 6 spark plugs failed and I had to stop and change the failed one. That happen probably 4 times last year.

Ayuh,.... Welcome Aboard,... What was happening to the spark plug,..?? How did it fail,..??

Goin' to a bigger motor will give ya more power, not faster speeds at the same rpms,.....

As Capt. Mello said, 6000 rpms is Way to many rpms,... 4800 rpms should be Tops,....

 

[jerryjerry05]

You will use more fuel.
The motor should be easy to put in.
I think the exhaust down tubes might be the same for both motors.
You will probably need a new prop too.

 

[mrwad]

One time plug spark failed after just leaving the port. Engine was prewired and outside temperature about +25C. I just leaved the port on about 15 km/h and then started to gradually increase RPM and speed. Then suddenly I have noticed lack of power and vibration as one cylinder was out in my V6 engine. I came back to the port and found one plug spark that was blowed up. Changed it and everything worked good for about a 3 weeks and then on full power 4500 rpm one plug spark failed again. I use NGK plug sparks so they should be fine.

Sorry everyone! For sure the boat runs on 4500 RPM doing 55 km/h, I said wrong (not 6000 rpm). Sorry I am kind new to boating. Used to km/h more than knots (as it should be usually for more professional discussion).

What is the point in bigger engine then? It will get to plane faster? I thought replacing V6 by V8 will give me lower RPM on 55 km/h and lower consumption or at least the same. On the other hand I understand that more cylinders and power means more fuel.
Would you suggest to service my engine rather than replacing it to V8 225D ?

Thank you everyone!

 

[Bondo]

and found one plug spark that was blowed up. Changed it and everything worked good for about a 3 weeks and then on full power 4500 rpm one plug spark failed again.

Ayuh,.... What is "blowed up",..?? How are they Failin',..??

Are the electrodes erroded,..?? Missin',..??

If so, look for poor fuel delivery, 'n the timin', as it sounds like detonation,....