1st hand knowledge of 350 small blocks in a 31.

Carl · Post by **Carl** » Nov 19th, '07, 16:51

Again this weekend I heard about a guy who had 350 smallblocks in his 31, supposed to be a Bahia-Mar. Guy told me the boat ran fine with them and had quite a few years on the engines with little issue. No specifics other then that.

I always seem to hear about someone who knows someone who had 350's in a 31, never the actual person with the engines. I don't intend to ever go this route, but for personal curiosity I wonder how the boat would perform with small block's. Would the engines die in short time or would the boat just be a dog and slush around barely on plane. I'd really like to hear from someone with 1st handknowlege of a boat powered with smallblocks.

Dug · Post by **Dug** » Nov 19th, '07, 16:54

There was one in Noank a few years ago. I think it is now on the Mystic River in CT.

The owner and the broker and the new owner all told me it ran fine.

I always thought what you said, that it would be a short lived set up. Seemed to be contrary to what they said.

I still like my Yanmars... :)

D

Ryan · Post by **Ryan** » Nov 19th, '07, 17:16

My Express Cruiser has 320 hp 350 Vorteks in it. It cruises around 24-25 kts. and does 34 kts wide open. Small blocks can produce the same amount of hp as a big block and have always had a longer lifespan. My boat does the same speed as a big block boat and burns much less fuel.

Capt. Mike Holmes · Post by **Capt. Mike Holmes** » Nov 19th, '07, 17:54

A guy in Freeport had 318 Chryslers in a 31 Bahia Mar hardtop, replaced them with 350's a couple of years ago, seemed happy.

John F. · Post by **John F.** » Nov 19th, '07, 18:18

We ran at 22 knots from NJ to Montauk a few years ago with a 31 Express that had small blocks--he did fine. A B31 around Annapolis (Jim Burk's) has small blocks and he likes its and gets similar speed to mine with 454s (20-21 knots). I never understood why a B28 is fine with small blocks, but a 31 would be considered underpowered--they aren't that different. 350s are great motors, but it isn't about hp--torque makes a boat go (ask the diesel guys)--and 454s have alot more torque at cruise speeds. Got me how this all works.

mike ohlstein · Post by **mike ohlstein** » Nov 19th, '07, 19:32

Try running a 31 with small blocks up the back of an 8 foot sea at nine knots......and you quickly learn what the fuss is all about.....

Hyena Love · Post by **Hyena Love** » Nov 20th, '07, 08:56

Torque is weak in the rpm range in which one would typically operate the vessel. Backsides will scrub your speed off and the engines will tend to struggle.

At the same time, I am convinced one can stand astride a Chevy 350, pour fuel down the intake out of a dirty bucket, and the engine will still run. Great engine, poor application.

Capt Dick Dean · Post by **Capt Dick Dean** » Nov 20th, '07, 11:28

Reading the start of this thread I almost believed it. Yes, the engines run fine. But the two senior diesel techs that were at the Mid Atlantic gig in July both said that it is torque that you need in a 31. And that's why diesels are so great as you can turn a bigger wheel.

When I told them I had 18x18 quad wheels the reply was "your over proped". Take an inch off the pitch and I would do better. They said that I was lugging the engines.

Futher more, just between you and me, top speed on my beauty was not disclosed. This put them in the dark. Just a little. Nor was the cruise speed.
The only stewards that know the data are CWJ and WindStar. Both are sworn for a tight jaw.

scot · Post by **scot** » Nov 20th, '07, 12:06

I have a single 350 small block inboard in the "For Sale" 22ft boat. Most boat manufactures do not put enough gear on them (IMHO). I set the boat up with a TD5011A 1.9:1 and 18x19 3 blade and it has excellent torque, for a small block gasser....gave up the top end but the bottom end and cruise are strong. Cruise is 22-23kts at 3200 rpm. WOT is 28-29kts at 4200 rpm. The engine is just a bit warmed over. Set up like this the 350's are not too effected by the load in the boat, or the sea state. Just don't expect to win many races.

Carl · Post by **Carl** » Nov 20th, '07, 13:08

Thanks Ryan. Finally someone who really has them in there. Gotta be better to work on then the Big Blocks. Can you tell me what rpm you cruise and your hourly burn? If you don't mind your reduction and wheel size as well.
Your numbers sound almost too good as I cruise about 20knts at 2950 rpm and burn about 22-24 gph. How is she in big seas? I know my 440's can struggle up the back of some waves, 3-4's I really start losing speed and could use more power.

Scot I agree with you, gear them right and the power should be there at cruise. Yes maybe a bit slower, loss of top end but I can't see why it wouldn't work. I think Ryan sort of proves that as he has a quick 31 with 350's, so if he cut back on the top end he should really increase the power in the cruising range.

Carl · Post by **Carl** » Nov 21st, '07, 10:37

Just thinking last night how many different ways our boats are setup.

Diesel's from Small-ish 4-53 140hp Detroits to Whalers 6-53TA's @ 400hp.

Gassers, Capt Mike Holmes mentioned one had 318 gassers running up to 8.1's, what's that like 500cubic inches plus.

Pretty large span of engines for a 31 foot boat. I'd love to go from one to another to see how each was different.

Not sure what it all means, but interesting. I can't think of too many other boats that go so far to each end of the spectrum.

34Hatt · Post by **34Hatt** » Nov 21st, '07, 12:29

Well another option is a 350 with a stroker crank that adds more torque and keeps the weight & size down. Makes for a nice in-between.

dougl33 · Post by **dougl33** » Nov 21st, '07, 13:31

The 8.1's are 496 ci.

Also, I'm not so sure I'm sold on Ryan's longer life-span comment. Maybe at 260-270hp, but I think its a little different when the 350's start cranking out 300+ hp. They just haven't been around that long at that rating to compare to a 330-350hp 454.

DRIFTER31 · Post by **DRIFTER31** » Nov 21st, '07, 15:38

Dan is right......A 350ci stroked to 396 with the right torque camshaft and a Holly injection system would put out the same torque # as older big blocks and could live a long time at 3200-3400RPM. But the 8.1 is a stroked 454 and at 496ci thats the king of gassers. The 396 small block would only have an advantage over the old 454 if using new roller camshaft and other beef up goodies aluminum heads etc. Add all that up and the 8.1 starts looking like a better deal

Carl · Post by **Carl** » Nov 21st, '07, 16:08

8.1 I hate the whole liter thing...496 is still alot of cubes but thanks for setting me straight dougl33.

Time will tell about the 300+hp 350's. But even with less hp I would think the 31 would perform okay, by okay I am thinking a cruise of 18-19mph in good weather with a moderate load.

Carl · Post by **Carl** » Nov 21st, '07, 16:10

What motor is the 502?

John F. · Post by **John F.** » Nov 21st, '07, 16:31

I think the 502 (8.2) is a siamese big block--no water jackets between cylinders. Mercuiser sells a 6.2/377 c.i. small block that they stroke themselves. Crusaders sells a 6.0/364 c.i. small block that is what GM replaced the 5.7/350 with. I asked a mercruiser rep. at a boatshow if I could get a copy of the hp and torque curves--they weren't available. To me, for a B31 its all about torque at cruise rpm. The 496s are available as 385 hp and 425 hp. I was told that the the extra h.p. for the 425 h.p. comes at high rpms, and that at cruise the numbers are very similar. So, unless you have a go-fast, there's no reason for the 425 in a B31--my 2 cents. The 496s are supposed to be great in a B31. I'd like to see what the 6.0 Crusaders would do.

Have a nice holiday everyone.

Anna E. came out today--on the hard until April.

John F.

Ryan · Post by **Ryan** » Nov 23rd, '07, 20:15

SIM,
The 350's I have in my boat are Vortek 320 hp's so they turn high RPM. I cruise them at 3300-3400 RPM at 23-24 kts and burn about 22 gph. Those motors are capable (so the manual says) of cruising at 3800. At 3800 it runs 27 kts but I don't know the burn since I never run it their for any length of time. WOT is 5000 RPM with those motors and the boat does 34 kts and doesn't feel good at thet speed. It's geared at 1.5 to 1 and seings 3 blade 16x16 with heavy cup. I have been out in heavy rolling seas and never had a torque problem running up backsides of waves. If someone doesn't have the money or need the range for diesels I believe the 350 is the best way to go in a 31.

Carl · Post by **Carl** » Nov 26th, '07, 09:35

Wow!

Someone really did there homework. It does not sound like you are over taxing the motors as I would have expected. Then again, I was thinking of 350's with 270 or so hp.

22gph at 22-24knts, much better then my 22gph @19knts with 440's 1:1.52 turning 16 square four bladers. If you ever get flow scans please let me know where your sweet spot is.

Did you decide to go with the 350's, bought it that way or...

Ryan · Post by **Ryan** » Nov 26th, '07, 09:50

I bought the boat without motors from Tom Oaks when he owned Holtz Boat Works. It was his recomendation to go with those motors. I figured out of anyone, he would know that they would work well for the boat.

Carl · Post by **Carl** » Nov 26th, '07, 14:36

Hearing your numbers, it sounds like he knew what he was doing. Time will answer the last question, will the 350 hold up? Years ago when Yanmar was just getting started in our recreational marine industry I was told those high revving Yanmars would never would hold up and I'd be throwing my money away on them. Stupid me I stayed with my 440's. Hopefully you got the new diesel alternative.

Best of luck with'em.
Carl

bertram31.com

1st hand knowledge of 350 small blocks in a 31.

1st hand knowledge of 350 small blocks in a 31.

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