Princess 266 Convert Petrol to Diesel

[krl]

I am new to the forum so Hi to all!!

I would like to change the twin AQ151/290 on my princess 266 to diesel. Originally princess use to fit AQAD31. I found a couple of 2nd hand 130 HP volvo diesel engine at reasonable but have the following question:
1) Will the z-drive (stern drive) match or do I need to get one as well?
2) Will I see a great reduction in speed?
3) Do I need to change all deshboard meters?
4) Will i save money on comsumption?
5) What model do you recommend?

Looking forward to reading your answers!. Thanks in advanced.

 

[Don S]

Re: Princess 266 Convert Petrol to Diesel

The 31's used the 290 drive, so it will bolt up. I will have to check and see for sure, but I think the gear ratio's are the same. The later 31's all used the duoprop drive. If you convert to that, it will make a huge difference and economy. Only the lower unit and props would have to change, not the complete drive.

The exhaust tube will also have to be replaced.
The two big rubber rings on the flywheel cover where it goes through the transom shield will also have to be replaced with the softer diesel rings. Absorbs more of the vibration.
You will need the diesel gauge and alarm panel. The tach is different, and the alarms are completely different from gas. So is the ignition switch.

5) What model do you recommend?

If they came with the 31, stick with it.

 

[krl]

Re: Princess 266 Convert Petrol to Diesel

Any more comments guys?

 

[HorizonblueDK]

Re: Princess 266 Convert Petrol to Diesel

The gear ratio for the 31 diesel is 1,61:1 for single prop and 2,3:1 for DP, so you will need to replace the lower outdrive, since your current drives has 2,15:1 ratio.

Depending on propeller, you will see the approx same topspeed as today, the 31 diesel is a strong engine, compared to the AQ151.

You will save on fuel consumption, how much I don't know. Depends on how you use the boat. 30% maybe more.

 

[krl]

Re: Princess 266 Convert Petrol to Diesel

What you said applies to AQ 171? I just found out I have the AQ 171 and not the 151. I am assuming I have the 290 out drive.

 

[HorizonblueDK]

Re: Princess 266 Convert Petrol to Diesel

Yes, the same applies to the AQ171 (16 valve 4 cyl), as they have the same ratio in the lower unit as the 151. Regarding the top speed, I still don't think there will be much difference. A couple of knots slower.

You have the 290 or SP outdrive, if it's still the factory installation.

 

[krl]

Re: Princess 266 Convert Petrol to Diesel

Dear All, i am changing the petrol AQ171A to diesel. I have found two reconditioned AQAD31 (130 HP 4cyl). The mechanics has told that they will fit my stern drive 290 SP. Is this correct or will I have to change the lower unit aswelll?

 

[HorizonblueDK]

Re: Princess 266 Convert Petrol to Diesel

You will have to replace the lower-units. The 4 cyl gas ratio is too low for the diesel engines.

The best option will be a set of duoprops with a 2.30:1 ratio, but that's gonna cost.

A pair of 1.61:1 ratio single prop lower-units will be fine.

 

[krl]

Re: Princess 266 Convert Petrol to Diesel

thanks Horizonblue.

So whether i choose the 1.61:1 sp or the 2.30:1 duoprop i just need to change the lower unit only? Just remove and replace ? or are there more hidden expensis?

How can I know what ratio i currently have on my 290sp.

 

[HorizonblueDK]

Re: Princess 266 Convert Petrol to Diesel

Remove the zink ring behind the propeller and the ratio is stamped in the housing. I'm not sure, but I think it is also stamped on the plate, that is under the steering helmet bolt.

It is correct that you just replace the lower housing, BUT.....

When you purchase a set of lower housings, be sure that the bearing race for the upper taper bearing (on the vertical shaft) is included. This ring is pressed into the upper housing and must follow the lowerunit.

When you start to install the "new" lower housings, this ring must be installed in you upper housings with the correct amount of shims under.(remove the old bearing race and sell them with the old lower-units)

The shimming procedure is described in the Volvo sterndrive manual.