ORIGINAL VS MODERN POWERPLANT

[rbay]

Looking for any and all input.

I recently purchased a 1973 CV21 to restore.  It has a newer Berkeley jet pump, but no engine.  The first two paths engine replacement could take are both in the same 300-350 hp range:
1.)  Replace it with an early 70's vintage Olds 455 big block like original.  Would at least start with a marine engine, possibly a non-runner for complete rebuild, or something more together.  I'm pretty certain I would use a Holly Sniper EFI fuel system and an HEI distributor, but otherwise pretty old school.  Would integrate into the electrical system, gauges, etc. like the original.
2.)  Replace it with a 2000's Mercruiser 6.2L engine.  Might be something needing repair, or drop in ready. Would have modern ignition, fuel injection, but no doubt present some challenges integrating it into the original dash and controls.  Might be a few $1000 more than the Olds, but worth it to have the later technology?

So when thinking about reliability, driveability, sensory, fun, resale, servicing, what would be your vote?  I know fuel economy will favor the newer engine, but Michigan summers are pretty short and I don't get to put that many hours on my boats, so that takes a backseat to the other factors.  Or am I missing some things to consider?

A third possibility would be a modern big block, like a 2000's Mercruiser or Volvo Penta 8.1L, which would be 375-400 horsepower and another few $1000 more....but would that be worth it?  Would the extra HP really result in a better boat?

Thanks for you thoughts.....option 1, 2, or 3?

[Plugcheck]

Why limit to three options?   What is the overall condition of the rest of the boat?   Just about anything can be configured to connect to that drive.    What is the long term thinking?   Period correct restoration?   Go fast have fun?   Honestly you could find a reasonable small block to drop in to make it operational for the 23 season, take what was learned and go forward in the fall.  Just some ideas

[rbay]

Hi Plugcheck,

To answer your questions:
1.) You're right, there are a lot of options.  I thought the three I chose:  original big block, modern small block (same HP), modern big block (more HP) covered a lot of the variants and would bring out the majority of the pro and con arguments.  On a personal level, I was a 30-yr GM engineer, so I have more experience with GM engines.
2.) As far as current condition, the original upholstery is in good condition, and I'm hoping the hazing on the gel coat will wet sand off.  Some missing pieces, the windshield frame and grab handle in particular, will be a problem.  But I'd still like to get as close to original as possible.  That said, there is no shortage of older hot rods and muscle cars being restored with modern motors.....this could be the boat version.
3.) Speed isn't my #1 priority.  This is about cruising around the local 800-acre lake with wife and dog, and having a high probability of getting back to the ramp without a tow.  Well, maybe a place diverter rooster tail would be cool.....

[carlsoncvx18]

If you do not care about originality. 

I would lean towards the gm6.2 they make a lot of hp and torque their light weight.   

[Plugcheck]

A mouse or ls would certainly be a cheaper build than a rat, although not as high on the cool factor.    The 6.2 is a fine powerplant, but the 5.3 shouldn't be counted out, powerfull and plentiful.    A place diverter is very high on the cool factor scale, but Im afraid Id get in trouble with one if I had it. Likely you are more responsible?.

[rbay]

Good words about the small blocks, guys.  I had ruled out the standard output 5.7L (250hp) since I have a psychological floor at 300hp.  But now I see there were some high output 5.7L MPI ski boat engines up to 325 hp in the late 90's.  Should be minimal electronics to integrate into the instrument panel.....I need to watch some videos or read some blogs or on-line articles related to the installation.  Has anyone in this forum put a newer inboard engine into a GC?

The Olds 455 jet boat engine is largely a western US thing, the availability of a used 5.7L HO ski boat engine east of the Mississippi should be much higher.  Biggest issue will probably be finding one with some hours left in it.....ski boats have a tendency to be used pulling towlines vs. sitting on sandbars.

My biggest temptation with a place diverter would be dousing an obnoxious stereo.

[Plugcheck]

I suppose one aspect of your selection criteria should be cost.    Ballpark what are you looking to spend?

[rbay]

I'm hoping these are reasonable amounts to buy a used marine engine and get it running well:
- 455 Olds or 5.7 L       $ 6-8K
- 6.2 L                        $ 8-10K
- 8.1 L                        $10-12K
(I don't think the marine 6.0L and 5.3L have been around long enough to get a deal on a used one)

I'll spend the extra money for the 6.2 L or 8.1 L to have a better boat, but feedback thus far has generally recommended newer, smaller displacement motors, suggesting stay at the low end of the scale.  The boat came with two sets of logs & snails and a bellhousing, so the installation cost for the Olds would be almost zero, all other motors will be another $1-2K to get the gauges and controls working (?).  I like the idea of a 1/2 closed-loop cooling system to avoid the high pressure problems when the jet pump feeds directly into the engine, so another $1000 there for the heat exchanger.

[Plugcheck]

Exhaust costs can be considerable if you opt for non Olds, considering you have those.   I have $3k in EMI thunders for BBC for comparison.  Wondering how difficult a 455 in good shape would be to find?   The dash gauges can work a variety of engines, so if you want to keep a classic dash, then there are ways to interface.     As for water control, my friends 23, 460 jet, we simply used a gate valve and adjust water flow for desired temps.  Wire it in the position that works best.    Seems to have worked well for several years.     Closed cooling has its good/bad.   If I was in saltwater, id certainly consider it, but we travel mostly in fairly clean lakes.   Missouri river is a bit muddy, but an end of the day flush seems to take care of that .     

[Plugcheck]

Found a 455 supplier out of Tyler TX that has a no core 455 offering for under $3k.   By the time you get it installed and set up probably be around $6k.   Would be a step towards period correct resto and all new.   BTW, ever consider a Billy Bob copy?
    https://www.mabbcomotors.com

[rbay]

Yep, the mabbcomotors pricing is what I've used to set up my financial baseline.  There's also an Olds 455 Hardin set-up with an extra short-block in Idaho, and a rebuilder in Spokane 8 hours away, that I've contacted.  Lot's of logistic issues there!  Would also end up about $6K.

I'm also watching a Mercruiser 5.7L MAG on the east coast, a 320hp MPI version of the GM small block for $5400.  It has wet exhaust risers, so don't I just run exhaust hose from there into my through-hull flappers?  I could see it run and haul it back on a Uhaul utility trailer.  It puts me right back in the old vs. new discussion at the same price point.

I'll take your cooling system input under advisement.  I'm reluctant to winterize my own boats and risk cracking a block, but would do a closed loop myself since the engine is already full of antifreeze.  That would save me about $200 per year.

My wife thinks it's cute that I keep watching the 007 chase scene over and over since I bought the CV21. That Billy Bob boat had a nasty paint job (all the land excursions) and exhaust pipes coming through the sun pad.....my daughters will want to be able to lay out!  I do like the twin swept antennas.

[ccv-19]

 Very few options for exhaust for the Olds motors.
 Dont need to worry about too much pressure from the pump
with the log manifolds . When you use the over the transom
open exhaust thats when there is a problem. With the logs
its mostly open flow .

[rbay]

New twist.
My neighbor is a great mechanic (cars, boats, planes).  He built a Chevy 454 for an early 60's Biscayne but ended up putting in a more period-correct 409.  So he may give/sell me cheap the 454.  I know I'd have to marinize the obvious things, maybe even a new cam.  Is a newer BBC a good compromise?
rbay

[Plugcheck]

The cam would need to light on the duration, BBC loves to suck water at idle.    Carb, fuel pump, and alternator should be marine items due to fire/explosion hazard.   Exhaust may be pricey and stock cast are way heavy.   I have a pair of cast BBC manifolds, but no risers that I would part with.

[rbay]

I have a parallel discussion going on performanceboats.com.  There's a guy there with a complete set of BBC logs/snails, engine mounts, bellhousing, PTO, driveshaft he would sell me for a pretty good price.  Yep, know about all the explosion-proof substitutions. Figured I'd need a new cam, maybe marine head gaskets.  I like the idea of the jet cooling water thermostats that manage the flow of water to the engine.

[carlsoncvx18]

Are you going to run in fresh water?  Standard felpro head gaskets work just fine. Had a set on my boat for 13yrs no problems. Haven?t touch it other 1 set of plugs.

[demian5]

I always through a supercharged 4-cyl motor out of a cobalt ss would be cool in my cvx16ss

[rbay]

I've had a lot of back and forth over at performanceboats.com and am now thinking to buy a used, complete pullout GM LS engine.  The best would be an LS2 - 6.0L/400hp, but an earlier and less expensive earlier LS1 - 5.7L/350hp would do great, too.  I think there would be quite a lot of intrinsic value in having "Corvette" logo motor covers in the engine compartment.  The lower end of these LS engines is rock solid (6-bolt mains), aluminum block and heads, and there are already quite a few marine application parts.  The unicorn seems to be the exhaust system.....going to spend $2K on manifolds and risers unless I can find a set of used Ford 351W logs and snails.  With some re-drilling on the cylinder flanges they fit.

[ccv-19]

 Ebay

[rbay]

That's a good deal, ccv-19.
Interesting they've sold 19.....maybe a low-production run?