View Full Version : Chris Craft engine question
10-18-2010, 04:12 PM
Along with the restoration of my 35' Lyman Express Cruiser I will be rebuilding both engines. The original engines are a pair of Chris Craft 350Qs rated at 235HP. I would like to get some more power out of the engines since I think 235 is pretty low for the boat. Crusader currently offers a carbureted 350 rated at 315 horsepower so I figure using a few tweeks I can at least achieve that. I have also considered rebuilding it as a 383 stroker. However, this boat being a cruiser I am more interested in fuel economy and range rather than acceleration and top speed so I am not sure which route would better suit the boat. The boat weighs about 13000 LBS and should have a top speed of about 35 kts according to the factory literature. The current engine is the 235 HP 350Q turining a 19X19 three blade prop. Any suggestions or comments on the rebuild/repower would be greatly appreciated.
10-18-2010, 04:20 PM
I have also considered rebuilding it as a 383 stroker. However, this boat being a cruiser I am more interested in fuel economy and range rather than acceleration and top speed so I am not sure which route would better suit the boat.
What you want to do is mutually exclusive. So do you want economy or speed? Speed costs.
If it were me and I were looking to add 85HP per side to my existing 45 year old small block motors, I would probably look for newer motors. But personally, I have no need to go 35Kts on a boat that has beds.
10-18-2010, 04:29 PM
Indeed. Speed = Fuel. Also, consider that after 45 years, they aren't making full power. If you are going to rebuild them, you can over-bore them, larger pistons, throw in a different camshaft, bigger carb and exhaust, you know, all the hot-rodder tricks. There are even Fuel Injection systems that can be installed without a ton of complication.
But this all costs you in fuel. Bigger engine = more fuel, more power = more fuel. you get the idea.
Peter Malcolm Jardine
10-18-2010, 04:29 PM
You could quite easily get over 300 horse per small block... but the transmissions you are currently using would have to be replaced. Most of the paragons that were small block rated wouldn't take that much horsepower.... because marine small blocks didn't produce that much in the 60's.
If you want to replace motors, then just buy new mercruiser efi's and be done with it. They will be a lot more fuel efficient and a lot less hassle than a couple of 40 year old engines, even if you rebuild them. The modern small block is a lot different motor, the block casting is denser and lighter, the heads flow better, EFI saves gas and maintenance over carburetion.
I have a 36 foot CC cruiser... with twin 283's rated at 185 horse each, mated with their original paragon hydraulic transmissions. I even use the points ignition. They were rebuilt completely about 6 years ago. My boat would be a lot heavier than yours, about 16000 pounds dry according the literature, and at full throttle (28 miles an hour rated) it consumes about 30 gallons an hour. They work well, but they're vintage engines, which I chose to restore. One of the reasons I did that is because new EFI small blocks with transmissions would exceed the value of the boat. That's also likely in your case. Rebuilding your current engines will cost about 8k if you do most of the work yourself, more if you farm them out. That's still a lot less than new power.
Your boat at 35 miles per hour would be slightly less.... maybe 20 gallons an hour. Even with new V8 power, I doubt you could get it much below that amount at full throttle.
10-18-2010, 04:54 PM
The transmissions are Velvet Drive with 1.91:1 reduction gear the trans shouldn't be a problem because the Velvet Drive is used on higher horsepower applications. I am not interested in speed, I am looking to get better economy out of the engines and reasonable performance. I was figuring with more power at the low end, I could get the boat up on plane at lower RPM and use less fuel. I know a prop change would most likely be required. The only reason I was thinking about a 383 is because they develop a lot of low end torque, but this may be overkill. I will probably just rebuild it as, however it doesnt look I can even get a base 350 anymore with HP as low as 235, Even the 350 CI Crusader Classic which is a basic carbureted engine is rated at 315HP. Both being basically Chevy engines I would think that if I used similar specs to the Crusader in terms of cam, pistons etc I should get a similar result. Or I could be completely wrong. I am not interested in re-powering with new engines because the fuel savings will never equal the cost of the new engines.
Peter Malcolm Jardine
10-18-2010, 05:05 PM
Yes, you could get similiar results, but your old engine block and heads are a lot different than a modern 350. You could use the basic block and crank and rods, with new pistons, new heads, new intake, new carb, but then you are starting to get close to new anyway. At that point, I would buy a short block reman and forget about the old engines.
Your velvet drive may take over 300 horsepower being a little later tranny than my old paragons... but they still need a rebuild anyway.
The biggest thing holding you back on better gas mileage is hull design and weight. The second part is engine technology.
10-18-2010, 05:14 PM
Keep in mind older engines tended to be modestly rated. You may find your 215 are closer to today's 300s!
10-18-2010, 05:30 PM
Thats true about the rating of engines. I dont know if the older engines were modest or if the newer engines are optimistic. Peter, Youre right about hull design and weight being a bigger factor than the engines most likely. Ill probably just end up rebuilding them to stock specifications, with a few modern upgrades for reliability sake such as point-less ignition, high energy coil etc. The CC 350Q was the most costly engine option for the boat, even more expensive than the 383 Chryslers so I figure Lyman thought the engine was well suited for the boat at the time.
10-18-2010, 07:57 PM
There you go. Keeping it simple is so much easier. If my boat had been delivered to me with small block OHV V-8s I'd probably still have them.
Peter Malcolm Jardine
10-18-2010, 09:24 PM
The engine question is a big one when it comes to the larger boats.... I am still somewhat surprised at the tendency of restorers to replace sixties vintage engines... I guess it takes a while for what we see as "modern" classics to catch up to earlier boats. We all know that if we took a 30's engine that was all there and replaced it with a modern engine in a period launch, it would devalue it..... but sixties boats seem to replace engines willy nilly. More of a comment in general rather than a specific comment on this boat..... I do find a greater prospensity to replace engines in larger boats than in open boats... reliability and efficiency being a greater factor.
For the record, most of the marine engines of that day tend to be about right in horsepower. They had cams that accentuated the torque curve, and used the truck block if there was one, forged crankshafts if there was one. In the sixties however, there was a tendency to want to present the most horsepower per cubic inch, and if you dyno'ed those old engines, they only hit their horsepower figures on their best day;) You can't use the car engines as a comparator, mostly because the marine version functioned at a much lower useable rpm.
When I rebuilt the 283's in Vanora, I was still (hoping) trying to accomplish reliability the way I see it now... Ain't gonna happen, but I can live with the idiosynchrasies I have (after some cussing) I tend to be more careful with 50 year old engines, even if I think they will take open throttle, I take them there rarely. That's mostly because I don't want to break anything. I have lots of spare parts that I have collected over the past few years, because they are not super easy to get. I remember when I bought the Vanora (a 1964 Challenger CC) I thought "Oh no problem, 283's, lots of them around" . They haven't put a new 283 in anything SINCE 1968!! :d
Opinion? I would rebuild those 350Q's... you can get decent reliability with what you propose, and for the record, the correct motor for the boat.. That may not be worth much now, but my guess is that 15 years down the road, it may/will be. If you want to do some extra work, get the rotating assemblies balanced, and the block line honed and carefully/thoroughly cleaned. If you have electric tachometers (can't remember) then you can also go to a high end HEI distributor. They tend to time better and as you've mentioned, the electronic ignition helps fuel mileage.
While you're going at it, replace the front and rear seals at LEAST in the velvet drives. Disc sets are not all that expensive either, so if you replace them, you get to clean the transmission housings out thoroughly, and yes, there will be ancient dirt in them.
Good luck. I enjoy reading your threads... very nice work.
10-19-2010, 10:55 AM
Rebuild the 350s. If you want better reliability and better mileage, go with an electronic ignition and multiport EFI. Multiport EFI doesn't make more hp at low revs because it flows more fuel; it makes more because the fuel flow is better matched at each cylinder, and no fuel is wasted. This also makes for better mileage due to less internal drag in the engine. If all the cylinders are getting the correct flow, drag is minimized. If some are too rich and some too lean (typical carb), not all cylinders are working up to snuff. If you REALLY think the engines will be undersized for the boat when they are rebuilt, stroke the engines.
10-19-2010, 09:15 PM
I agree with you about the engines. The original engines do add something to the boat that it just wouldnt have with a new pair of crusaders. I have decided to keep them stock and do normal upgrades such as balancing, align hone, HEI etc. I have one engine sitting in each corner of my shop, and each time I look at them more sure I am that I want to just keep it stock. An added benefit is that it is easier and cheaper to keep it stock as well. I will look into what is involved in rebuilding the velvet drives as well. I may take them off the engines and bring them home since my shop is an hour away. It would give me somethign to do after work.
10-20-2010, 12:01 PM
There are lots of small details that will net you some "free horespower" and by free horsepower I meant power that you don't have to pay for in fuel. (it's still gonna cost to do the mods) While some people have already quit reading my reply and started typing about how I don't know what I'm talking about just stay with me for a minute. Two degrees and a couple of decades experience in engine building behind me qualifies my opinion as more than just a ramble from an idiot. If you want to increase power without paying for it at the pump you have to increase the efficiency of the engine. Things like better ignition, roller rockers, better flowing heads, better designed intake, etc will all add up to small power gains coupled with small gains in fuel efficiency. It's a win-win situation :)
The '96-99 Vortec truck heads (350ci) are some of the best flowing, efficient combustion chamber heads made for the small block and will fit your engines with no mods other than a newer intake manifold since the middle bolt angles are differnt on the vortec. The bonus is that they are also cheap :)
There are more, but I won't waste your time if you're not interested so just let me know. My 1965 Impala was my daily driver up until a couple of years ago and after I built the original 283 engine and added an overdrive transmission it was dyno'd at 317 horsepower and gets 26mpg on the highway. I have 44,000 miles on it since I rebuilt it and it's still just as good as day one. Just because the block is old doesn't mean it has to be handled with caution nor do you have to fear it breaking down at any moment.
Anyway, just a thought.
10-20-2010, 01:26 PM
Thanks for the information I would be interested in talking to you further regarding the engine rebuild. I have read that the newer vortec heads are more efficient than the older 350 heads. The problem for me is that the intake on my older engine has a different bolt pattern, and it is a water cooled intake. If I changed the heads and intake I would also have to make some modifications to the cooling system which I am not sure if I am up to. Shoot me an email at email@example.com with your contact info, I would like to bounce some ideas off you if you dont mind,
10-20-2010, 03:16 PM
Peter Malcolm Jardine
10-20-2010, 03:54 PM
Just because the block is old doesn't mean it has to be handled with caution nor do you have to fear it breaking down at any moment.
Nope, engine blocks don't usually break down on 50 year old engines...on 60 and 70 year old ones they do. Starters, alternators, water pumps, cooler assemblies, and transmissions do though. Certainly if you swap out enough parts for modern stuff, most of those problems go away completely.
I chose not to go to a modern head and intake, carb or ignition and sometimes I think that was a mistake;)
10-21-2010, 09:16 AM
I had these engines in an old chris craft i had. They are heavily customized by CC to be a low profile motor. They have a unique goose neck intake manifold that ties into a sherwood circulating pump (not traditional auto style pump), they use the mallory flat cap distributor and a low profile carter carb. They are also flywheel foward ( basicly installed backward) so the bell housing is custom and the transmission hook up is different from most gm. You also have true counter rotation ( not using the transmissions) so becareful on the seals etc on a rebuilt. THere is a lot of information on these motors on old chris craft sights. they were consider very good motors. The pumps are getting expensive.
you can not just start changing carb, intake manifold etc. they will not fit.
10-21-2010, 09:36 AM
10-21-2010, 04:57 PM
I meant 35MPH, according to the original brochure.
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