How's the 350 merccruiser run ?

[bgreene]

I see a few Tsunami / Sceptre's with 350 I/O mercs and wonder ............

1. Are the I/O's not too good in salt water use ?
2. Hows the fuel burn and performance ?

[FLexpat]

My '76 Sceptre has a 260 HP 350. With the original pre-Alpha drive and the cav plate even with the keel WOT was about 40 mph, Cruise about 23-24 and it got just a bit under 3 mpg (I think ~2.8). It is probably a good functional minimum I/O power package. The original 233 Ford block wasn't quite enough and got replaced. The 350 worked really well in salt water for a lot of years but that took a bit of maintenance.

In this rebuild I'm replacing the original pre-Alpha (died from corrosion) with a Bravo 1X and setting the cav plate up ~2"; hopefully better performance and the drive is capable of handling a lot more torque. The Bravo has a 1.65 ratio versus the 1.47 in the Alpha so the prop will turn slower with more pitch. The 350 is going back in for now but I wish it was a 383 stroker or something with more mid-range torque than the 260 HP version of the 350. In an ideal world I'd put a L96 or LS3 in it, but I suspect it will end up with the stroker in a couple of years.

[bigeasy1]

My setup and results are similar to the above reply.I have a 350 260hp Mercruiser,with an Alpha drive in my 74 Tsunami.
My top speed is right around 38-40 mph (gps)and I cruise around the mid to high twenties at about 3200-3500 rpms.Somwhere I have my fuel burn numbers from the Flo Scan,and I think that depending on water/wave/wind conditions,and weight of fish and crew I'm burning anywhere from 9 to 12 gallons per hour at cruise speed.
My setup is raw water cooled,not the best in salt water,but I fish the great lakes,so it isn't an issue for me.
If money and time were not an issue,I'd love to change the out drive to a Bravo III dual prop setup,but I think the Alpha will have to do the job.
Without a doubt,outboards have more pros on the salt than outdrives,but a well maintained fresh water cooled outdrive can give you good service on the salt.

For the fishing I do(salmon trolling)I love the outdrive setup.The boat never stops moving forward,all our fish are netted off the stern so the high transom,and lack of outboard engines and rigging make netting big kings easier.In over 25 years of salmon trolling,I can count on one hand the times I had a fish run forward of the boat(a very ugly scenario)
The out drives are definitely more prone to corrosion,as they can't be tilted completely out of the water,and a disadvantage for fishermen like me in the northern areas is that I have to make the decision to pull the boat out and winterize it at some point.
I can't just decide to fish a nice day in november or in early march,as I'd have to re-winterize it each time I did.
That wouldn't be an issue with an outboard powered boat.

[RUSTYNTABATHA]

couple questions as i am going to look at a seafari with the 233 still in it... the current owner claims that it only needs an exhaust mainfold ... so if i can replace the single bad manifold are there any other things i need to be looking for ... and when replacing the for 351 for the 350 chevy is it a drop in project or is this a PROJECT ... ?? I would like to get this thing and get it running good so i can tear down the 20 MA .. and i didnt want to be without a running seacraft while doing this ..

[FLexpat]

I would never replace just one manifold on a V configuration motor so plan on two and the risers also. The 351 has the distributor up front so that's nice for access. The 350 is actually about 1" narrower so that comes in handy too. Changeout isn't a a huge deal - the 350 motor mounts are a couple of inches further forward than the 351 IIRC. Both are good motors if maintained. Either way I'd think about pulling the motor just to look at the inside of the transom housing; the Y tube is prone to corrosion on the bottom and that sinks boats. Pulling the motor is a 1 day job (2 hrs if you really hustle). A little longer going back in since you have to align the drive.

Also, the 233 was only made for a few years in the mid 70s so parts are not nearly as available as for the chevy blocks. That also means it isn't even close to a new motor. Fortunately good 305/350s or 4.3L V6s are pretty cheap used.

[bigeasy1]

DO THIS FIRST



THEN DO THIS



Of course I did this reply mostly in jest,
but it worked out best for me.I yanked out the original Ford engine(first photo),and replaced it with a 350 GM (2nd photo)and am glad that I did.
I bought an older Chris Craft Scorpion(donor boat) with a rotted transom and used it for the GM engine,and Alpha outdrive.It only had 200 hours on it as the owner put in a new short block.
I bought the boat and trailer for 1500.00, used the engine and drive, and gave the rest of the boat and trailer away.It was an inexpensive deal.The guy I gave the ChrisCraft to
for free,made a center console out of it,he was happy

I had thought about keeping the original ford power plant,but it needed a fair amount of work,and it had a lot of hours on it.Parts for the Ford marine engines are much more difficult to find,as compared to GM.
As mentioned, parts for the GM are extremely easy to find,and the prices are reasonable as well.I'm a big Ford guy,but the GM 305-350's are a sweet running engine and have been around so long,and have such a proven history of durability,that I think it's the way to go.

Good luck with your project Btw,like Flexpat,I would have loved to put in a nice new 383 stroker,but it was out of my reach with the green backs

[Islandtrader]

Different boat...but just for comparison. I have a 383 stroker, bravo 1 and 350 ponies.

Nice cruise speed, is 28-30 and mpg is 3.1 with a burn rate of approx. 9 gph. Top speed just over 50.

[FishStretcher]

Gen I bravos 3s have a corrosion issue, but I think you can help with some gen 2 anodes and the mercathode system.

I have one that is pretty terrible looking from sitting at a mooring and never being maintained, but it seems to work fine so far.

I haven't been able to air out my bravo 3 setup yet- the 25 footer had tank trouble. Previous owner said mid 40 kts with a 350 MAG MPI and 22" counter rotating props on a 1:2.20 lower unit. Just noodling in a river without space to air it out, I blew thru 32 knots when I bumped the throttle a little before I could pull it back, so I think I believe it. I wasn't anywhere near WOT. It hooks up well, and slows the boat very quickly when you chop the throttle.

[pelican]

Originally Posted by bgreene

I see a few Tsunami / Sceptre's with 350 I/O mercs and wonder ............

1. Are the I/O's not too good in salt water use ?
2. Hows the fuel burn and performance ?

Bennett h !!

depends on what configuration - meaning,carb'd or injected

the MPI motors are the best ! smooth,very fuel efficient - my sea craft,350 MPI bravo I drive cruise @23/25kts,depending on conditions - 3 nmpg

stern drives in salt water:

lots and lots of poor information out there

truth is,no there's no problems with stern drives biggest problem owners have,these are self inflicted ! read that as poor maintenance practices.drives need to be pulled every season - bellows checked,gimbal bearing checked - u joints lubed/checked

every 5th year,manifolds,risers and bellows should be replace...

click this thread - http://www.classicseacraft.com/commu...ad.php?t=23364


there's a whole host of good information given about servicing and upkeep on stern drive set ups

[Bigshrimpin]

Anyone use these Stainless-Marine Manifolds? I just got 2 sets of them with a project hull.