Volvo 270 to 290dp Lower Swap

[Mknick]

Hey All,

Exploring potential performance upgrades for my recently acquired 1974 Glastron Caribbean V-254. It has dual Ford 302's("Glastron 165's") and volvo 270 outdrives. I am looking at swapping to Mercruiser outdrives as well as upgrading to newer Volvo drives.

Everything is stock on it as far as I can tell, power steering, power shifting, and the 270 outdrives.

No trim cylinders to be seen (so not 270t's). I am considering doing a lower leg swap, keeping the upper off of the 270s, and getting 2 290dp lower units and joining them up with the 270 tunnel and upper part of the unit. As far as I've read this is possible with some proper shimming.

My main reason for doing this is better low end performance for getting on plane, and slightly better gas mileage.

I wish I could swap out the entire thing for a 290dp or newer with trim cylinders, but that seems to be a hefty project that might not be worthit with the transom bracket differences as far as I know.

I have also considered leaving it with the 270's on it, but I feel like the 290dp's would be better suited to the boat.

With all that being said,

1. Is trimming the lower units up a big impact on performance on a 25' cabin cruiser? (weight of 5500lb+) How much of a performance loss am I looking at by continuing to use an outdrive that does not have trim, and relying solely on tabs instead of both trim tabs and outdrive trim?

2. If I stuck with 270's, what am I looking at performance wise for hole shot and top speed vs 290dp's. I should note, I am considering upgrading to 351w engines, with them being a direct upgrade to my current 302s. I'm assuming the 290dp's will win all around, but if anyone had any experience on this, I'd love to hear about it to help decide one way or another. It's supposed to be a 40+ mph boat as it sits now.

3. Are there any other issues comparing volvo 270 and 290dp outdrives as a whole? Maintenance, reliability, parts availability, etc.?

4. I know that swapping out enough parts to get a trim system is pretty much out of the question without pulling the motors(as far as I know, without counting the 270t outdrives) If anyone has any additional advice in this area, I'd love to hear it as well. I think that I would pretty much have to swap out the entire thing if I wanted trim, including inner and outer transom brackets, which is an obvious pain.

 

[Scott Danforth]

My main reason for doing this is better low end performance for getting on plane, and slightly better gas mileage.

I wish I could swap out the entire thing for a 290dp or newer with trim cylinders, but that seems to be a hefty project that might not be worthit with the transom bracket differences as far as I know.

no such thing as "better gas mileage" on a power boat. if you want slight increase fuel economy go to diesels. if you want a big jump in fuel economy, move to sails or slaves with oars

Hey All,


No trim cylinders to be seen (so not 270t's). I am considering doing a lower leg swap, keeping the upper off of the 270s, and getting 2 290dp lower units and joining them up with the 270 tunnel and upper part of the unit. As far as I've read this is possible with some proper shimming.

My main reason for doing this is better low end performance for getting on plane, and slightly better gas mileage.

I wish I could swap out the entire thing for a 290dp or newer with trim cylinders, but that seems to be a hefty project that might not be worthit with the transom bracket differences as far as I know.

I have also considered leaving it with the 270's on it, but I feel like the 290dp's would be better suited to the boat.

if you swap to 290's you will need to find a hyper-rare 290 PDS housing for a ford and swap over the transom shield and back. or you can get a ford to GM trans adapter from companies like kennedy engineering or transdapt and then space out the coupler the same thickness of the adapter. this would require you to move the front mounts a bit. at that point, you will be repairing the fiberglassed in mounting blocks.

why are you enamored with the obsolete ford motors? Just find some GM V8 290DP's from the late 80's to early 90's and drop them in. in the short run, it will save you hundreds, in the long run, it will save you thousands

1. Is trimming the lower units up a big impact on performance on a 25' cabin cruiser? (weight of 5500lb+) How much of a performance loss am I looking at by continuing to use an outdrive that does not have trim, and relying solely on tabs instead of both trim tabs and outdrive trim?

2. If I stuck with 270's, what am I looking at performance wise for hole shot and top speed vs 290dp's. I should note, I am considering upgrading to 351w engines, with them being a direct upgrade to my current 302s. I'm assuming the 290dp's will win all around, but if anyone had any experience on this, I'd love to hear about it to help decide one way or another. It's supposed to be a 40+ mph boat as it sits now.

3. Are there any other issues comparing volvo 270 and 290dp outdrives as a whole? Maintenance, reliability, parts availability, etc.?

4. I know that swapping out enough parts to get a trim system is pretty much out of the question without pulling the motors(as far as I know, without counting the 270t outdrives) If anyone has any additional advice in this area, I'd love to hear it as well. I think that I would pretty much have to swap out the entire thing if I wanted trim, including inner and outer transom brackets, which is an obvious pain.

1 - no, not much. more response to trim tabs on big boats.
2 - change your props. you get either better hole shot or top speed. cant have both even going to duo-prop drives. however there are trade-offs with duoprop drives as well. the benefit of a duoprop drive is the near instant holeshot.
3 - very few parts are same between the two. in the much later years, the transmissions are the same. you should go thru the parts diagrams and the service manuals. your 270's most likely have the 10-spline input shaft
4 - yes, you need to pull the motors, and swap transom shields if you want to get away from the 270

 

[Mknick]

no such thing as "better gas mileage" on a power boat. if you want slight increase fuel economy go to diesels. if you want a big jump in fuel economy, move to sails or slaves with oars

I laughed so hard reading this...

if you swap to 290's you will need to find a hyper-rare 290 PDS housing for a ford and swap over the transom shield and back. or you can get a ford to GM trans adapter from companies like kennedy engineering or transdapt and then space out the coupler the same thickness of the adapter. this would require you to move the front mounts a bit. at that point, you will be repairing the fiberglassed in mounting blocks.

why are you enamored with the obsolete ford motors? Just find some GM V8 290DP's from the late 80's to early 90's and drop them in. in the short run, it will save you hundreds, in the long run, it will save you thousands

Awesome, thank you for the advice.

I'm not really stuck on the old Ford's, just making it a project as is and going from there.

When you say GM V8 290DP's, I assume you mean the whole powerplant, not just the outdrives. I'm not against this idea, or potentially a hybrid setup in the future.

Do you have any good sources for used or remaned GM V8 290DP's?

Do you think that short term doing a 290dp lower swap with the existing 270 uppers would be good for the foreseeable future? I could probably sell the existing lowers off the existing outdrives as well.

Or should I just stick with the 270's until I decide sooner or later to upgrade to GM V8 290DP's? I don't know if the upgrade will be worth the time going from a 270 to a 290dp lower at this point.

 

[Scott Danforth]

build the motor yourself from brand new parts for $3000 each (a stroker is just a bit more)

buy a re-man from your local machine shop for about $1800

plenty of 290 drive parts out there. a whole bunch in the Seattle CL

your on your own trying to marry the 270 to the 290. a 280 to 290 has been done. not a 270 to 290 that I know of

I would stick with the 270's until you get the hull restored. your first order of business should be looking for rot

 

[Mknick]

build the motor yourself from brand new parts for $3000 each (a stroker is just a bit more)

buy a re-man from your local machine shop for about $1800

plenty of 290 drive parts out there. a whole bunch in the Seattle CL

your on your own trying to marry the 270 to the 290. a 280 to 290 has been done. not a 270 to 290 that I know of

I would stick with the 270's until you get the hull restored. your first order of business should be looking for rot

Thank you for all the advice Scott. I should post some pics, but the hull itself is fairly clean. Could use some paint. Fiberglass floor with no cracks, so no water getting in there. The transom is solid as far as I've checked, but I haven't done a core sampling yet. May give me an excuse to repower sooner rather than later, along with a transom rebuild.

The other forum I found on the 270 to 290dp swap is here if you're interested. Not sure if the guy was successful. https://www.offshoreonly.com/forums...vo-penta-outdrive-expert-w-270-280-290-a.html

 

[Scott Danforth]

if you read the article, its a 280, not a 270.

and yes, the 280 and 290 have the same lowers. making it easy to swap if you re-shim the one bearing.

the early 270's share nothing with the later 270's other than decals, etc. since the 270 went thru many changes from your early 70's version to the late 80's/early 90's versions

I would run what you have and take core samples of the stringers and transom, get past that hurdle and go from there.

 

[Mknick]

if you read the article, its a 280, not a 270.

and yes, the 280 and 290 have the same lowers. making it easy to swap if you re-shim the one bearing.

the early 270's share nothing with the later 270's other than decals, etc. since the 270 went thru many changes from your early 70's version to the late 80's/early 90's versions

I would run what you have and take core samples of the stringers and transom, get past that hurdle and go from there.

"Also Scott I think you have a Volvo 270. Not sure how a 280 cover got on it. But the D/P bottom should bolt up to the mid section with no issues. Shimming is done in the top and bottom independently and should not affect one another. If the (bottom or top) unit was shimmed proper before it should be as simple as swapping the two sections out."

They at first thought it was a 280, but someone else thought differently. Again, I don't know, can't trust everything I read on the internet. I need to find some service manuals somewhere.

Found another writeup where some guy says he did it successfully:

"I have actually done that exact swap and it was on a circa 1969 boat as well. I was after the power trim transom assembly and not directly after the dual prop although that is all confined to the lower unit so it could be swapped at any time. i got the transom assembly off a mid 80's Bayliner that had one of those funky DOHC 4cyl's in it so i knew the gear ratio would be wrong and luckily the upper gear section was backwards compatible with the older mid so after some mixing and matching i came up with a 290 mid/lower mated to a 270 upper mated to a 290 transom. From my experience nearly everything was a direct swap. Come to think of it i may have used a VP 285but i think they all interchange from that family"

But then again, he had to pull the engine still. And with the 290dp lower/mid and the 290 transom, it would be prohibitively expensive. Time to seriously consider a Merc based setup.

 

[Scott Danforth]

FWIW, i picked up an entire 290 DPA1 (same year and p/n as my drive) from transom shield to one prop for $425 which also had a 290SP lower in the pile. The trans was blown. Picked up a trans for $200.

thats my spare pile for when I blow something up

You just have to have time and look

As stated, a pile of 290DP parts on Seatle CL. Watch your parts, you cant mix and match. You must look at the service manual and the parts list. To many changes along the way