Hybrid 4.3 camshaft questions

[IOmmSocket]

Hello, first post. I'll introduce myself : I'm Jake. I own an auto repair shop, been an ASE master tech for 15+ years. Just getting into boating - and I like an arduous project. I have had a couple of boat "projects" into and out of my life that I didn't really get wet with. I just picked up a 1990 Sea Ray 200 overnighter with a 4.3/alpha 1.

The engine in the boat turned over, wouldn't fire, and when I opened the block drain valve (was still "winterized") it was full of water. The oil was also full of water. I went no further knowing there was a significant failure and decided the boat needed a full engine refresh. Because I like to get in over my head and figure out the best way out while under fire I went ahead and bought a vortec 4.3 from a 2001 silverado and tore it down, discarded basically everything besides the block and heads. I brought those to my local marine machinist and had the block bored .020, crank and cam holes align bored, heads smoothed, and a couple of faulty valves replaced.

I've got the engine in my shop on a stand for assembly now, thinking I would just throw the cam from the 1990 engine into the vortec and it'd be a marine vortec - oops. The camshaft is very clearly different from the vortec - looks like much more duration with less lift, both are rollers. I've looked all over the internet in every place but the right one for good specs on the 1990 marine camshaft, the 2001 truck camshaft, and any vortec specific marine 4.3 camshaft and have come up dry.

First question in this whole series of fun is where can I find specs for these camshafts? I'd have to assume a truck cam would have low end torque a boat would want, and being stock I couldn't imagine it would have too much overlap - then again this was an EGR motor so it may. The other problem I'd have with the truck cam is loss of potential - does the truck make a lot less HP than a comparable boat and is this directly pertaining to the cam?

 

[Scott06]

General consensus is truck cam will work. You can also call your preferred cam supplier or order a factory mercruiser one
part number 431-803186

 

[achris]

.... The other problem I'd have with the truck cam is loss of potential - does the truck make a lot less HP than a comparable boat and is this directly pertaining to the cam?

We come up against this all the time. People calling out for 'more power', (like Tim Allen in 'Home Improvements' :facepalm without understanding exactly what that means (in terms of the trade-off between top end and mid range power).

So, more power in a car is great. You have a gearbox with which you can keep the engine running in the power band... Boats, not so much. The ratio in the drive and the propeller pitch are what you have, from idle to WOT... And unless you're planning on racing, most (over 80%) of the time you're going to be below 4,000rpm. So the question is why you would sacrifice mid-range torque for top end power that you are rarely going to use? But it gets worst... When setting up the boat with regards to propeller pitch, we select what we think will be about the right pitch, and take the boat for a test run. Then based on what the engine achieves at WOT we change prop to get the right pitch to meet the right WOT RPM. And if you have an engine that makes a lot of top end power and is very 'average' in the mid range, you need to prop for the top end, which leaves the engine struggling in the rev range you'll be wanting to operate in....

So, you can get a nice fat cam, make 280hp out of that 4.3L, but suffer with the engine being underwhelming when cruising, struggling to even get on the plane and generally being close to 'undriveable' most of the time. You'll hate it and be dis-satisfied in the boat generally.

The other option, use the truck cam, pretty much as mild as you can get, have the engine making around 210hp, but with a really strong pull right from idle. The engine and the boat will have great acceleration, and will cruise with ease.

Good luck,

Chris.....

 

[Scott Danforth]

the vortec cam that is in the 4.3 marine engines is about the largest cam you can put in a 4.3. the 4.3 marine motor is just on the raged edge of reversion at about 225hp at the crank (about 205 at the prop)

your 1990 motor isnt a vortec, an ASE master tech would know that.

you would also know it isnt a balance shaft motor as those came out in '93

the vortec motors came out in 1996

the truck cam should be fine, however i would get the crane cam that Mercruiser uses.

make sure you use the marine circulating pump, marine head gaskets and brass core plugs

jumping from a non-vortec to a vortec means you need a new marine intake, and you should get the proper engine mounts for a balance shaft motor. the motor mounts you have are fluid-filled for the non-balance shaft motor

another thing, you will be jumping about 4 generations on the accessory drive. you have a bit of work to get the accessory drive from the 1990 motor to line up.

 

[IOmmSocket]

Scott06 - I appreciate the general consensus, and thank you for the part number!

Chris - Sorry I must have misled you as to what my goals are - I'm not by any means trying to achieve a 280hp v6. If I was shooting for big power numbers I would V8 swap. My inquiry was more directed to the camshaft itself from a mercruiser 4.3 of the vortec variant, which I do not have. I wanted to compare the specification of that part to the specification of the 4.3L vortec from a truck.
My concern with leaving power on the table is not anything to do with peak HP, I want to know what the torque curve is. I've read enough threads on a variety of forums to see all the "more power" guys go nowhere, I'm by no means trying to frustrate any veteran with this inquiry.

Scott Danforth - I'm sure 225 is reasonable, I don't expect a ton from the little guy. The original motor from the 1990 is most definitely not a vortec, I did not mean to imply that. The replacement motor, however, is a vortec. The original was the 170hp variant with a 2bbl carb.
The balance shaft has been removed from the new motor, so I will be keeping the dampened mounts. The plugs and head gaskets have been replaced with marine components, and the pump will transfer over from the old engine. I'm moving from the old 2 barrel to a 4 barrel which meant new intake anyways. I will be using the old accessory drive, none of the components on it were faulty & I don't mind periodic belt adjustments.
What are the chances that you have either a part number or a link to the crane cam that you are referencing? I find nothing on their website for V6, nothing on the internet for Vortec engines - they all have mechanical fuel pump lobes.

 

[achris]

If you have a balance shaft block, put the balance shaft in and change the mounts to 'solid' (non-fluid).

These camshafts appear in the search for 262 V6. One of the 1200 to 5000rpm ones would do fine.

https://www.compcams.com/products/c...-c.i.-90-degree-w/-balance-shaft-(1992+).html

Chris......

 

[Rick Stephens]

I have a pre-balance shaft block with Vortec heads, plain ol' Edelbrock Performa intake and an Edelbrock 1409 carburetor in my boat. I stuck with the fluid mounts. I like it. Not that it matters, really, but a balance shaft uses 15 HP to spin, from what I read back in the day I built this motor. The cam is roller type right out of the stock '92 truck motor the block came from. I haven't had any issue with it, and can't claim any knowledge of its lift or overlap.

I run 100% in inland clean water. So the non-marine all aluminum intake is fine. If I was running in salt I would get the marine version with the bronze water passageways.

After running this motor for 4 years, I wouldn't spend anything to 'upgrade' to a balance shaft. It just doesn't matter to me. The motor runs fine and gets some long cruises on the big lake I normally fish. I don't notice a vibration at 1700-1800 RPM that is the reported reason for the balance shaft. Only time I spend at that RPM is when pulling wake boards.

Sounds like you'll have fun building it up. I'll follow along and feel the deja vu.

Rick