Bought a new long block and wondering about the coupling and gimbal bearing.

[AKJohne]

Ayuh,.... The ground the housing, so the temp sensor can work,....

Is the housing not grounded through the bolts into the intake manifold...?

 

[alldodge]

Is the housing not grounded through the bolts into the intake manifold...?

Yes and no
Yes its grounded thru the bolts but over time rust and corrosion takes its toll and things stop working or working correctly

This is why Merc added the brass rivites to maintain connection.

 

[tank1949]

Good thoughts for sure, transom was redone, has a knock sensor, verified that it works with a timing light and fluke scope. Tapping on the block retarded the timing and scope could show us how many milliseconds it was retarded.
Motor was rebuilt by prior owner of motor for his own use. He bought some used heads, lapped the valves and ran it for 30 hours. Rolled the boat over. We bought the motor and drive and ran it for 500 plus hours. Intakes were thin, it was just a matter of time, but yeah, I was concerned about detonation as well.

something warped valves. 500 hrs is not really a lot if properly maintained. Good luck!

 

[AKJohne]

something warped valves. 500 hrs is not really a lot if properly maintained. Good luck!

Thanks, I make luck. One valve warped because someone took some heads off a engine or bought them from a bone yard, touched up the seats and stuck them back in. These are $4.00 valves at todays prices in Alaska. We bought the motor in 2012, they would have been cheap valves then, IF they had been new. Which, I repeat they were not. FYI, valve's are primarily cooled when they transfer heat to the valve seat, if that cheap used automotive valve starts to get hot, it pulls further away from the seat and temps climb. Soon the valve no longer seats. The timing was right, the carb was right, the fuel was clean, the temps were normal until the valve warped. Its what happens when you use car parts in a marine application. I would prefer if you refrained from commenting. Have a good day and good luck.

 

[achris]

What is their function?

Return path for an electrical signal. IE, temperature gauge.

And before you ask, no the great big steel bolts holding the thermostat housing to the intake manifold don't do the job. Been down the 'I replaced my thermostat and now the gauge doesn't work' path too many times...

Chris...

 

[AKJohne]

Return path for an electrical signal. IE, temperature gauge.

And before you ask, no the great big steel bolts holding the thermostat housing to the intake manifold don't do the job. Been down the 'I replaced my thermostat and now the gauge doesn't work' path too many times...

Chris...

I appreciate the explanation, I have run a paper gasket the last several seasons w/o any corrosion or issues with temp sensors. It was a cast iron intake on the old motor, now aluminum, which shouldn't matter. However the housing is painted.

 

[achris]

I appreciate the explanation, I have run a paper gasket the last several seasons w/o any corrosion or issues with temp sensors. It was a cast iron intake on the old motor, now aluminum, which shouldn't matter. However the housing is painted.

Yeah I know, doesn't seem to make sense... You have 2 great hulking chunks of metal bolted together and you have no electrical path. ‍♂ Seen it with ma own eyes! (And more than once). Bolted up all snug and tight, with paper gaskets, no path (high resistance). Pull it apart and put riveted gaskets in and now it's path to ground (no resistance)... Go figure...

Doesn't happen all the time, but often enough that Merc only recommends the riveted gaskets.

Chris....

 

[Lou C]

Interesting….this isn’t an issue with the OMC/Volvo thermostat housings which can use a plain old Chevy water neck gasket; in fact I coat that gasket & bolt threads with Evinrude gasket sealer yet never had a problem with the temp gauge. I’m thinking this is because OMC/Volvo have the temp sending unit in the intake manifold not in the stat housing…

 

[nola mike]

Its what happens when you use car parts in a marine application.

You realize that there's no difference in the valves, right?

I would prefer if you refrained from commenting. Have a good day and good luck.

Good luck with that.

 

[Lou C]

This brings out a whole new question though….are there really any differences between GM auto heads and marine heads? I’ve looked at sites that sell both and it seems that there “may” be differences yet the differences are not spelled out. Some listed as marine are a good deal more expensive as well, but that’s probably simply because they are branded “Mercruiser” which seems to increase the price by at least 50%.
When I needed reman heads for my 4.3 the only thing available were stock auto heads so that’s what I used. And so far so good.
Valve overheating and distortion in marine inboards is related to fuel mix, fuel octane, ignition timing but also proper propping. I think you’re better off propping it to just reach 5,000 rpm if testing when lightly loaded because this allows some margin when loaded.

 

[tpenfield]

As far as cylinder heads, my previous 454 engines had the #10114156 cylinder heads on them. I believe they are used in some automotive applications and are also found in marine applications. Listings of the head casting mostly say '1991 and up', but do not say specifically 'marine'.

I think the bigger difference may be in the head gasket, where a marine engine would want parallel flow from the block, through the head gasket, to the heads and some automotive applications may have sequential flow (less coolant flow holes).

 

[Bondo]

This brings out a whole new question though….are there really any differences between GM auto heads and marine heads? I’ve looked at sites that sell both and it seems that there “may” be differences yet the differences are not spelled out. Some listed as marine are a good deal more expensive as well, but that’s probably simply because they are branded “Mercruiser” which seems to increase the price by at least 50%.
When I needed reman heads for my 4.3 the only thing available were stock auto heads so that’s what I used. And so far so good.
Valve overheating and distortion in marine inboards is related to fuel mix, fuel octane, ignition timing but also proper propping. I think you’re better off propping it to just reach 5,000 rpm if testing when lightly loaded because this allows some margin when loaded.

Nope,..... Just as with long blocks, the differences are in the parts used in the castings,.....

 

[Lou C]

The only things I have consistently read that are differences:
head gaskets
core plugs
cam grind
but nothing really relating to cylinder heads
I think a lot of people who wind up having trouble like that are not propped correctly but are not aware of it having not really tested if the engine reaches its specified max rpm.

 

[tank1949]

Thanks, I make luck. One valve warped because someone took some heads off a engine or bought them from a bone yard, touched up the seats and stuck them back in. These are $4.00 valves at todays prices in Alaska. We bought the motor in 2012, they would have been cheap valves then, IF they had been new. Which, I repeat they were not. FYI, valve's are primarily cooled when they transfer heat to the valve seat, if that cheap used automotive valve starts to get hot, it pulls further away from the seat and temps climb. Soon the valve no longer seats. The timing was right, the carb was right, the fuel was clean, the temps were normal until the valve warped. Its what happens when you use car parts in a marine application. I would prefer if you refrained from commenting. Have a good day and good luck.

I have been building marine Chevy small blocks for decades. My only two valve issues were due to a used boat that I bought, and the former owner didn't have distributor locked down. It eventually moved and advanced timing too much and warped all of them. Shame on me for not verifying timing. The second was due to a rusted out water passage allowing sea water into chamber. The so-called recondition heads were supposed to have never been used in a marine environment. Bull! It has been my experience that improper timing causes most valves to warp. But, I agree, if you install cheap crap, don't expect miracles. Good luck!

 

[AKJohne]

In regards to heads, specific details can be hard to ferret out. When I was "shopping" and decided to buy a new long block I considered a new GM 6200 briefly, I say briefly as They were NA at that time. Essentially the 5700 and 6200 are the same except for stroke, the head castings are the same, however the 6.2 did use different valves and possibly seats. I have forgotten the specifics now but the parts were better suited to higher temps, possibly iconel, could have been ss. As I said the exact details were hard to come by. The 5.7 & 6.2 are designed for marine, truck & industrial applications. IMO, its primarily camming and valve train.

 

[AKJohne]

I think both the 5700 and 6200 use 906 heads,
This is what I recall when I was shopping, the 6200 used Inconel and the 5700 was not.
"L31 Vortecs comes in two different casting numbers, 10239906 (#906) or 12558062 (#062). Originally, the stock #906 casting head was available in two versions. One version had an Inconel exhaust seat with single angle valve grind and was available on one ton trucks. The other version was the traditional three angle valve grind. Other than that, the #906 is the same as the #062 head."

From
https://www.chevyhardcore.com/tech-...tecs comes in two,available on one ton trucks.

Bottom line as others have said, is heat is the killer of marine engines, and the heads take the abuse if things are not right. and point is well taken and I do want to make sure things last. We were propped at 4600+ with the old motor, I will run the same prop for break in. Maybe on this motor I should be propping at 4800...?

 

[Lou C]

That's a big boat for a 5.7, I think the closer you get to 5000 the less strain on the engine every time you pull the boat up on plane. The other unmentioned factor is outdrive gear ratio, there are situations (like this big boat, not so big engine) where a higher numerical drive ratio might be better, same reason less strain on the engine when pulling the boat up on plane. I'm not so familiar with the Alpha and its gear ratio selections, but many people here are.
You already have closed cooling which by itself is superior to raw water cooling because the coolant is pressurized and that will prevent localized boiling that can happen in hottest parts of the cooling system, which is why raw water cooling systems are set up to use low temp stats.

 

[AKJohne]

That's a big boat for a 5.7, I think the closer you get to 5000 the less strain on the engine every time you pull the boat up on plane. The other unmentioned factor is outdrive gear ratio, there are situations (like this big boat, not so big engine) where a higher numerical drive ratio might be better, same reason less strain on the engine when pulling the boat up on plane. I'm not so familiar with the Alpha and its gear ratio selections, but many people here are.
You already have closed cooling which by itself is superior to raw water cooling because the coolant is pressurized and that will prevent localized boiling that can happen in hottest parts of the cooling system, which is why raw water cooling systems are set up to use low temp stats.

It is pretty heavy when loaded (close to 7K), bottom is narrow and that maybe helps. It did quite well with the other motor, typical cruise around 3200 give or take depending on conditions and typical cruise was 25-32 MPH at 2 MPG. WOT about 38-39 MPH. I rarely give it WOT other than to check the prop, gear ratio is 1:57 and even I dont usually firewall it getting on plane. Every now and then conditions are right and its fun to give it "full junior". Once on plane MPG doesn't change much.
Old motor indicated WOT 4400 to 4800, not sure what the new motor is, but thinking closer to 5000, so good advice on propping towards that number. I was hoping this motor will have a tad more power and maybe can go with more pitch.
Currently running a 15.8 X 15, 3 blade Solas, I tried a 16 X 16 Merc prop and it was a bit much.

 

[Lou C]

I have mine propped to 5000 WOT because I think my boat is a little big/heavy for a 4.3-4bbl (approx 4000 lbs) I have a Cobra drive with a 1.62:1 ratio and a 15.25x15 prop. This lowers the top speed as expected but the reduction in engine strain is well worth it. I could also use a 15x17 for a bit more on the top end. As it turns out our boating conditions rarely allow WOT for more than a few min so the 15 pitch works out better all around.

 

[AKJohne]

Correction, 1:47 drive ratio.