Mercruiser to Volvo Swap - full restoration

[PolishedPerfectionNE]

Alright guys, I finally joined this site after lurking here for the last year soaking up much needed information! I came across a 1979 Carver Santa Cruz 26 last march that a kid locally was giving away to anyone who could move it. I knew a couple of boat movers, and decided this may just work out for me. The boat came with a seized motor currently in her, but had another motor with 300 hours on it that could be purchased for 500$. Everything went relatively smoothly getting her back to my fathers shop - he does fiberglass work, auto body, and has a metal shop. We build handicap accessible vans and build everything from cutting the roof off to interior finishing. All tools and supplies could be sourced for a good price.

The hull is solid, deck is solid. Flybridge and all lower steering cables were all good and moved freely. The outdrive just needs new zincs. Trims tabs are good and work. The only bad besides the motor ( which mechanically I am inclined - I do all my own automotive repairs to my diesel, only thing I haven't done is a transmission at this point. ) were the windows were rotted and I don't even see how Carver ever thought these windows would last. I cut and removed all the rot around the windows, new Marine plywood installed and 3 layers of fiberglass cloth were added inside and out. Gutted the interior, Rebuilt the back wall of the cabin, have the front two windows installed and have to order new custom side windows next. The interior is redone and painted with mildew resistant boat finish. non slip on the isle and new cabinet that was fully glassed. Finally after a year of balancing building a new business, starting a family, and every other monkey wrench life can throw at you... I'm at a point where I can attend to the motor. which was removed and stored inside for the past 6 months.

NOW here is where I need your marine advice because I know automotive and there are some obvious differences.

The original power plant is a mercruiser 5.7 260 hp. the outdrive is a "pre alpha" I believe MC-1.

The motor I have to replace this is a Volvo Penta 5.7. I need to check the serial numbers tomorrow because I've been searching for hours on here and I thought I had this down to a 96-2001 carb model. I believe it is a GSI.

Please excuse my terminology as from my automotive standpoint all I see is a GM block 350. the mercruiser "bell housing plate" matches right up to the rear of the Volvo and the motor mounts stay the same. The outdrive input shaft should in theory slide right thru the transom and match right up the exact same way as the mercruiser motor had. From what I have read across these forums is that the Volvo motor MUST run the Volvo exhaust manifolds and, correct me if I am wrong, then my mercruiser transom assembly Y pipe will not match exhaust wise with the risers. I do not see this to be an issue as I am sure its possible to fabricate a stainless pipe to connect with rubber boots and hose clamps.

I need to get the model number tomorrow and find out what the exact horsepower rating would be. I believe this new motor may be more HP. I have a "pre alpha" outdrive and I do plan on using this boat to go fishing, and always want to get home safely. How reliable is this outdrive? would it be worth it to swap an Alpha transom assembly and I plan on buying a complete rebuilt outdrive no matter which generation it is.

Some people say the alpha gen 1 will bolt up to my pre alpha transom assembly? is this true?
everyone says the alpha gen 2 will not bolt up to alpha one or earlier. is the second generation any better or just cosmetically it looks better? would it be worth it to skip right over the alpha one if i'm swapping transom assembly anyway? or just go for an early bravo?

Need real experience on this because as I said I just started a family and if a front moves in while i'm out and the waves do kick up a few feet, i'd like to know i'm not going to shear a shaft and be literally dead in the water.. I used to work on a lobster boat and I know how it is out there. Best job I ever had! I'd like to get back out and do some commercial fishing this year.

I rebuilt the whole boat to my liking and removed the flybridge to lower the center of gravity. Really pushing to get her out and running by April with May 1st the latest!! New manifolds and risers, water pump, thermostat, starter, are all on the way shipped. Need a new alternator, and i'm replacing the steering cable, and will continue to do so regardless of its condition for safety/reliability reasons every 2-3 years.

thanks guys any help is greatly appreciated!!

PS I will post pictures shortly. Interior wise don't hate on my fiberglass work as I this was my first learning experience doing any of this. I'm not afraid to try new things because how else would you learn!! I can always re-do it next year but there's a lot on the table to be done in the next 8 weeks!

 

[wrench 3]

I guess you've been here for a while but welcome aboard anyway.
The 1-R drives had a weak spot on the vertical shaft at the pinion gear in the lower unit. I've seen them break on a 165 hp inline six.
The alpha one will bolt to your bell housing. (the one outside the boat)
The main improvement in the alpha one gen two was the water pump but the alpha one pump was fine as long as it's maintained.
The bravo is definitely stronger drive but the alpha is rated to 300 hp.

 

[Scott Danforth]

First....welcome aboard

unless your replacing everything, the only thing you need to worry about is unbolt your broken '79 block, and bolt in the new block. you have to find a coupler to work with the bigger flywheel bolt pattern.

your going from a Gen 1 GM SBC to a Vortec (late Gen III SBC). while most of the dimensions are the same, most of the post 1986 motors come with the larger 168 tooth flywheel vs the 153 tooth that your motor most likely has. you will need to use your MC-1 bell housing with your MC-1 drive stuff. so you may need to source a flywheel.

there is no such thing as a pre-alpha. you have an MC-1 drive.

no, the A1G2 stuff wont bolt directly to the Alpha or MC-1

 

[PolishedPerfectionNE]

Thank you guys that was extremely quick! and exactly the info I needed! I probably should have asked months ago but always try to find the answer via the search option first! I would have to assume that I can swap the flywheels from the seized motor 153 to the new motor 168? and the shaft on the alpha is shorter than the mc-1? but I should be able swap out those shafts too?

 

[achris]

V8 input shafts... MC1 and Alpha are the same length (The shorter shafts were used on the MC1 inline engines.).

If you are looking to replace transom assemblies, yes, go straight to a A1G2. The Alpha One is stronger than an MC-1, and will bolt up to the existing MC1 transom assembly. The Gen II will not bolt up to anything but a Gen II transom assembly.

The only reason I can think of for the statement 'Volvo engines MUST use Volvo exhaust manifolds' is for the cooling system plumbing. If you take all the plumbing from the Merc, you can use Merc manifolds. The heads are the same (And you're right, it's a 350GM engine).

Chris.......

 

[PolishedPerfectionNE]

okay thank you for the info! I had read that the difference between the motors were all internal like compression and the manifolds had to match to help with the proper cooling across all the cylinders or early engine wear and failure could occur. has anyone ever heard of this? I know you're supposed to replace the manifolds every 5 years as proper maintenance so I can always cancel my Volvo manifolds and find mercruisers

 

[achris]

The engines are the same. They all came off the same GM production line. Here's the Merc 260 spec alongside the Volvo AQ260 (note the compression ratios).... I can also confirm that the initial timing and total advance is also the same.



Chris.....

 

[Scott Danforth]

your new motor is a vortec so your existing intake manifold wont fit the heads. however your newer motor should have the intake manifold on it.

 

[PolishedPerfectionNE]

you guys are amazing! such good info so quickly! can't thank you enough! does this forum have a minimum post requirement to put pictures up? I'm going to go thru all my files later and get some updated pictures also

 

[achris]

3 posts. You're at 4, so :thumb: Just make the pictures less than 200kb each.

 

[wrench 3]

I don't think anyone answered your flywheel question. GM changed the bolt pattern in the crank shaft in 1986. So the older flywheel won't fit.

 

[PolishedPerfectionNE]

Thank you! all these little things that I would have never known about until actually trying to fit the parts together and end up wasting a day(s). incredible forum you guys are running here! busy day today I didn't get to the boat. hoping tomorrow

 

[PolishedPerfectionNE]

steering post - steel frame with 1/2" plywood- covered in fiberglass cloth and just resin on the inner walls. bondo sprayed with leftover clear coat to seal. then painted with leftovers. note on the candy camo pattern - should have primed first but we didn't have any laying around

 

[PolishedPerfectionNE]

long hair fiberglass mixed with kevlar to try and blend some of the cabin lines. I tried to building everything stronger than the original. then short hair to try and cover my horrendous fiberglass work. also this was in January during the coldest spell we had - 10* roughly all week working inside. trying to heat and cure this was all very fun! but January was my only down month with no work have to do what you have to do! the original fiberglass cloth work was laid over the summer when I cut and replaced all the plywood.

 

[PolishedPerfectionNE]

Now she is finally completely watertight! still had one small drip coming from what I found to be one of the hand rail mounts around the side - always thought it was my fiberglass cloth work somewhere with a pin hole

 

[PolishedPerfectionNE]

had some tinted fixed trailer windows sitting around the shop. brand new - just had to fabricate trim rings and screw them in. an inch or two too small but I really needed light in there. I only had two extension cords to work with and one being dedicated to the light was killing me. can always get customs later but the side windows should go forward enough to give me plenty of view

 

[PolishedPerfectionNE]

I could spend the rest of my life working the fiberglass to be perfect but I have to really keep telling myself - its a fishing boat, extra bondo work will not catch you more fish? I suppose its enough of a justification for me. I didn't bother with the middle sections of the walls as I do plan for windows to occupy most of the area obviously. she seems solid and smells wonderful compared to the musty-ness that was present originally. I will probably re wrap all the cushions inside with a matching red vinyl like the steering post. of course I can't find any of the original photos - ill have to ask my brother if he may have any. she's come a long way!

 

[PolishedPerfectionNE]

I tried to resize and I could only go down to 240x320 I hope thats fine!