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Converting a 280 SP to DP

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douglcfl

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I have a Volvo Penta AQ225 with a 280 single prop outdrive. I was given a working 280 DP lower unit and want to know if it is feasible to swap out my SP lower. What issues would I run into?
 
The swap is relatively easy and requires five new O-rings and one gasket. Two o-rings for drain plug/dip stick, three o-rings for the lower (oil tube, main bearing and lower pivot tube) and one red phanolic fill plug gasket.

You'll want the original DP vertical shaft tapered roller bearing race that was up inside of the Intermediate housing that the DP lower was removed from. Not a good idea to inter-mix these races, although it has been done. If no original race, new would be best.
Shimming procedure is spelled out in the workshop manual. This must be followed.
NOTE: this is a Negative pre-load, not positive.

NOTE: remove the exhaust flapper from the interior of the exhaust bellows. No need for this restrictive part when the DP will have an external back flow prevention flapper.

NOTE: this may not be a 280 DP. During/after the DP -C drive, some of the vertical shafts from this point on, are shorter. If so, this will require the long spline coupler. All else pertaining to the install is same.

NOTE: the over-all ratio of the Duo Prop lower must be 1.95:1 for your AQ 225, unless this is a very small light weight boat. In some caes, the 1.78:1 may work. Best to stay with the 1.95:1.
The 2.30:1 will NOT work.

The transmission must now run on the lower driven gear (vertical linkage piece is now on Port side). FWD shift raises this linkage, eccentric piston rotates CW.

The gear oil now changes from engine oil to GL-5.


Special note: Each prop requires a small spacer ring immediately ahead of the propeller. This is a thrust washer. Without them, you will cause damage.

You will use the B series (aluminum) or the C series (SS) props only (no thru hub exhaust for this drive). No exceptions! Props must be used as a set.... no mixing/matching.
Test props as you would for a single prop drive, as per OEM specs...... WOT RPM being the target.

Have fun, and wear neck brace protection! :D
 
Thanks for the reply, that is very helpful. The DP lower came with the aluminum props so I am set there. I was also told I would need the long spline coupler and that was included as well. Don't have the roller bearing race so I will get a new one, any suggestions on where to purchase this?

This is going on a 24 ' Sea Ray so not really a small boat. How would I confirm the gear ratio on the lower?

Thanks again for the help... :cool:
 
douglcfl said:
Thanks for the reply, that is very helpful. The DP lower came with the aluminum props so I am set there. I was also told I would need the long spline coupler and that was included as well. Don't have the roller bearing race so I will get a new one, any suggestions on where to purchase this?

This is going on a 24 ' Sea Ray so not really a small boat. How would I confirm the gear ratio on the lower?

Thanks again for the help... :cool:
Click to expand...
First of all, be prepared that the props may not be correct for you. A WOT RPM test must be performed, in order to determine which props will work.

The over-all gear ratio (if no one has changed the gear set) will be stamped into the prop shaft bearing carrier.
Remove props (this should have been done prior to purchase.... hope that they are not corroded in place) and remove the "ring anode" and wire brush the AFT-most area of the carrier.
The numbers will be exposed once clean.
For this boat, you will want the 1.95:1 over-all ratio.
No other will work.

.
 
Good news is that the props came off without to much trouble. I cleaned up the bearing carrier as much as possible, couldn't find the gear ratio any where. If I can't find it stamped on the unit is there any other way to determine the gear ratio?
 
NOTE: this is the area that would be covered if the ring anode was still in place.

In all my years, I have never seen one that has not been marked from the factory!
The exception would be a drive that has had a replacement carrier installed..... in which case the tech forgot to stamp it.
I let one slip away once that did not get marked.

Look very closely..... not all digits are always stamped. A 1.95:1 may read 1.95 only.

The other two ratios are 1.78:1 and 2.30:1 for this particular drive.
 
I may need to clean it up a bit more, it has been painted over and is a bit rough. I'll give it a closer look tomorrow. Thanks again for all the help.
 
could always mark the propshaft and rotate the driveshaft in gear. If it takes a bit less than 2 revolutions to turn the propshaft 1 revolution, you are in luck

If it takes a bit more than 2 input revolutions to get the props around once, you are out of luck.

trick is to make sure the cone clutches are fully engaged, and you take up any gear lash by going in 1 direction only

were the props 'A' or 'B' props. A is for diesel
 
Thanks for the tip. The input revolutions are definitely less than 2... Now that means it could be 1.95 or it could be the 1.78, correct?

The larger prop is stamped B4 854325
 
Your prop set is B-4....... That's about all you need to know..... still doesn't mean they will be correct, however. My guess would be 2's or maybe 3's tops.

Hystat is correct, as long as you have the lower bolted to an Intermediate and transmission that is free from an engine.
But you would be changing the lower unit ONLY.... correct?


If you were to do this, you will want to eliminate any slack between when the sliding sleeve locks up, and when torque is in place!
It could be done to determine the ratio.

Remember..... this is an "over-all" ratio, and takes into account the transmission reduction as well.
There is not a whole bunch of difference to be seen between the 1.95 and 1.78..... but enough if you were to test several times.

You could also do the math. I believe that the trans ratio is 26:27. Not sure, somewhere I have this written down.

Easiest way is to wire brush the aluminum carrier off and read the numbers.... if they are there and visible.



If I can make time, I'll spin a 1.95 for you ... or give you a gear count, and post the numbers.
 
I was finally able to clean the carrier off and read the numbers. It is 1.95

My next question is would you recommend a newbie that is mechanically inclined try the swap himself. I have done a lot of work on automobiles, including brake jobs, tune ups, carb rebuilds in the old days when we had carbs, etc. I am an IT engineer and build computer systems, so I am not afraid of a technical challenge. At the same time I want this to be right and can't afford a mistake that damages my drive. There is a local shop that is a Volvo Penta dealer that estimated $ 300 to do it for me. Is that good? My fear is the shimming procedure and the preload. I am not familiar with it and it might be worth the $ 300 for the peace of mind when I get this in the boat and turn the key... :) What do you recommend?
 
douglcfl said:
I was finally able to clean the carrier off and read the numbers. It is 1.95 .....................
My next question is would you recommend a newbie that is mechanically inclined try the swap himself. .........................
At the same time I want this to be right and can't afford a mistake that damages my drive.

There is a local shop that is a Volvo Penta dealer that estimated $ 300 to do it for me. Is that good?

My fear is the shimming procedure and the preload. I am not familiar with it and it might be worth the $ 300 for the peace of mind when I get this in the boat and turn the key... :) What do you recommend?
Click to expand...
I'm hoping that Andrew does not mind me sending you to the Vault "shimming procedure when changing lower units", rather than me typing all of this out for you. You'll find that I have explained it fairly thoroughly.
Use your Volvo Penta OEM work shop manual (not Seloc/not Clymers) for the instructions on taking dimensions A and B and for doing the math.

As for the $300 ..... I'll tell you this;
Minus the time to drain the oil, remove the single prop lower, install the DP lower, and re-install the new GL-5 gear oil...... the actual shimming task itself (shimming dimension check, calculating the new shim value, installing the new shims above the race, etc,) takes someone like me approximately 15 -20 minutes to do.
This is prior to beginning the lower unit re-install.
The entire job can require as little as 2 hours.... with prior experience. It will take you longer.

The physical portion is very simple...... doing the math is critical, in as much as knowing that this is a "NEG Pre-Load".... not positive!

If you are in an area where not too many work on the AQ series V/P's, then you'll want to ask questions regarding this (even the pros occasionally have trouble with this, if they do not routinely work on the AQ stuff)!

It usually takes as much time for oil R & R, cleaning mating surfaces, etc..............., as it does for the actual work.

I'd pocket the $300, and give it a try. If nothing else, you will have reduced the amount of work that the shop will need to do.
The $300 may now become $150. I can't image that it would take your shop any longer than it would take me!

You MUST use all new O-rings and fill fitting washer/gasket.
 
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I am going to give it a try. I have reviewed the shimming procedure and it doesn't look that difficult. I'll be building a stand for the drive and getting started this weekend. I am going to start by removing the SP lower from the drive and cleaning the mating surfaces of the DP lower. Then I will take the measurements and do the math a few times then come back with some questions. I figure I'll do a few trial runs and educate myself first.

Thanks for all the input. I'll be back for more...
 
Yes, odd as it may sound, it requires several to many measurements to come up with a consistant reading.
You need to tap the bearing race down evenly and equally onto the roller cage of the lower unit.
Tap the vertical shaft down as well. It must be seated onto the angular contact bearing that is beneath the roller cage (you cannot see this bearing).

Take many measurements...... use the one that you come up with more consistantly.
Likewise with the "bore" in the bottom of the Intermediate housing.
I have never found one good reading at first attempt.
You will need some small value OEM shims. The thinner/the better, as you can create more combinations with these.
Grease works well to hold them in place.
Better order these ahead of time.

A good depth mic and a standard micrometer is all you need.

I also glue the pivot tube O-ring into the bore of the lower unit. Grease it prior to the install.

You will do just fine!

Oh.... btw, a long 1/2" carriage bolt (14" or so), with a heavy sleeve of some sort on it, double nutted at the threaded end, makes an OK slide hammer for removing the race from the bore of the Intermediate housing.
The carriage head will hook the race, and allow you to remove it with the sliding action.
Otherwise, it's a bitch to remove one.


NOTE: if the race will not come back out of the bore of the LOWER unit, apply a bit of heat to the aluminum case, grab what's sticking up of the race, with a huuuuuuuge channel lock pliers. It must come out, in order to be driven into the Intermediate, while capturing the new shims above it.
 
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