The elusive 224/3.7 MerCruiser banger

Wrong engine

 

X2

 

You don't want it. They feel like they have 1/3 of the power of the 3.7 even though it has 2.5 liters. The 2.5 is an underperformer and in a boat, salt water can run through the engine so they rust very badly and freshwater freezes and cracks the block so they have short lives. I have personal experience with them. They were the chevy 2 car engine. Still in production as an industrial engine, common in forklifts. Sold as boat engines in 16 to 18 foot boats for many years . Very easy to work on it is a car engine, parts are all available and can be resleeved when the cylinders rust through. And they will.
For an engine go to a boatyard. Useable 3.7s needing work go for $100 because they don't like to fix them when others are much easier. Runners cost more. A man in business has a reputation to maintain but individual sellers don't.
The one thing I'd avoid on a used 3.7 is bores too large for strong cylinders. To begin with, the cylinder walls are thin. Overbore them too much and they are like tin cans. If you can find one, buy one that has never been overbored. The common first bore is 30 thousandths over because that is done to cars. 20 over is better and is doable. 40 as a last resort. Yes real gurus can sleeve them but I consider that as walk on water level genius.

The good thing is that boats don't get much use but some sink and the engines can get very wet.

 

Should I pull the trigger on the speedmaster head now? What are the odds of it ever going on sale again. It was on sale for IIRC $300 last December but in this economic environment who knows.

 

I think they may run a big sale for the 4th of July. Unless you are going to use it between now and then, I'd wait.

 

I was waiting for the Black Friday sale to order some transmission parts from Speedmaster. Of course, the stuff I wanted didn't go on sale. I want to say the bare unported 460 head was $230 at one point. That will probably never happen again.

 

Doing something right, by accident.

Expecting increased fuel consumption after having reduced my engines compression, I
Wanted better fuel economy, so I added a vacuum advance to my mercruiser distributor,
the engine mechanical advance at 1000 rpm was 12 degrees mechanical plus 6 degrees vacuum.
at 2000 rpm it was 36 degrees mechanical plus 6 degrees vacuum the advance was all in at that point.
It worked really well, the engine did nor knock, had more torque where I wanted it and revved ok too.

The rest of the story. Early on I had the block zero decked at a friend's advice. I used a favorite cam profile and the engine made good power and didn't knock (it cranked at 170 psi) but it did run hot. I tried a stock cam that knocked badly at more than 28 degrees ignition advance and it ran hotter , 1750 for exhaust gas temp (this cam had 210 psi cranking).

To fix knocking, I had the Elgin cam reground to my profile and as the engine was apart, I changed to the low compression bathtub pistons. ( cranking at 135 psi). The low compression ratio allowed me to run more ignition advance .

Now the engine has much better torque than ever at the low rpm end where I drive, it revs freely we will find out about heat and fuel consumption when it quits raining here.

("Big Chief" alluded to the above compression ratio decrease very early in this thread.)

 

What's your static CR before and after the piston change?

 

I can't give you good numbers on this right now as this is on two engines and my records fill five note books . Static compression ratios do not mean a lot ,( especially as I kept changing things) dynamic is much better but it is frustrating to calculate when you know the numbers can't come out right.
I have much more faith in cylinder pressure which is what really matters anyway

I looked in some of my notes and did not see the Initial ratio. I ran stock pistons, rods and 102cc Dovc head . the crank throws were un modified but the deck was milled 80 thousandths and the head gasket when compressed was 31 thousandths thick. I got away with it because of the cam profile and it was zero decked. Both engines were zero decked. I took the salvageable parts of the first engine and used them on the second. The cam profile made much more difference than one would expect. I remember one old calculation at 9.7:1. The second engine was bored ten thousandths more than the first engine. The second engine head was milled 20 thousandths late in the process changing the compression ratio numbers that I never recalculated.
I calculated the final ratio at slightly over 8:1 with bathtub pistons but that was before the head was milled. The bathtub pistons have a different compression height but they come up level with the top of the deck so they are both zero decked engines. The first engine was good until its block split but the second engine (mostly a block change) seems to run stronger.

I calculated dynamic compression ratios and have more faith in them but I'll have to look them up .
Frustrated with the calculations which were subject to a number of variables I just went with cranking compression comparison as it could be relied on and it is what the engine "sees".

 

There is excellent information on " Don Terrill's Speed-talk."
Look for "Quench height and ignition timing".
the final post explained how it all comes together and it applies directly to us.
Especially to those of us who run at reduced throttle settings.

 

had to do this one by one

 

second page

 

third page

 

last page I took an hour to type it and still could not post it

 

Bigchief wrote this years ago, I repost it here so you don't loose it in 95 pages

 

Just stumbled on this on Facebook.


Guys there claim that they have used this successfully in boats. I don't have first hand knowledge, but without the big nose it should fit when using an automotive bell housing. At 1/5 the price of the other one used by guys on here, it might be worth a try.
I just bought the expensive one or I would have bought one of these to give it a try on my stock engine.

 

When I look that starter up is says it fits the early air cooled VWs. I doubt that the bolt pattern or tooth mesh is correct. Those motors were up to 1.7 L so I doubt it would spin ours. I see it isn't gear reduction.

 

Like I said Beck, the boat guys on FB said it worked for them. I would have to try it myself to be convinced.

 

Has anyone tried to strip the black paint off the block ? If so, how did you do it ?

 

I think Beck glass beaded his. I tried but my machine was to small. So I used paint stripper. It was a giant pain in the butt and still looked like crap. I finally just painted it with a dull aluminum paint.

 

• I had access to a bigger glass bead blaster and used that. You have to really be cautious when doing this. The blasting media gets into EVERYTHING. For example, the oil pressure relief valve needs to be removed and replaced or at least cleaned. The oil galleys need to be scrubbed well with the plugs out.
• I don't know what kind of paint that black stuff is but it is amazingly durable, even to blasting media.
• Jeff Calkins commented, " Yeah and if you are not the one doing the blasting, damage could be done."
• Jeff is correct. The aluminum will begin to blister with enough time spent in one spot.
• If the black paint is in pretty good shape I would try to lightly dust it with a blaster to give a new coating something to bite to, then give it a coat of quality paint. With no use at all my block is showing a little paint peeling. I thought I had used quality products. I used an epoxy self etching primer followed by a single stage urethane.

 

Thanks for the input.

I always liked black stuff, rattle can freindly.........

 

Paint leaves an organic surface that radiates heat faster than bare metal. If done to excess, thick paint will insulate an engine.

The black paint Mercruiser uses is insanely durable and excellent at preventing corrosion . I painted one mercruiser engine orange with rattlecans, over the black paint which I cleaned with acetone and the paint stayed on. But there is nothing wrong with a black engine and it has the advantage of making parts which aren't supposed to be there hard to see.

If engine appearance could present a problem, screw the hood on. An onlooker wanted to see my engine so I handed him a screwdriver saying "there are 110 screws to remove and you have to put them back". ( there were actually only 58 screws ) but he silently handed the scredriver back.

 

I bought a small geared starter made to fit our mercruiser engines. It was less than $60 (new). It is lighter and does start them but it does not have a lot of power. I also bought a very small alternator from them but had to go to a wrecking yard for a plug to connect it. The seller is DB electrical .

 

Found a pair of heads on racing junk. Seller is asking $1200. I haven't asked him if he'll sell a single head.

Am I an idiot for passing on a passing on that?

I'm inclined say no because:

1. The compression chamber is small and I'd need to dish my stock pistons if I want it to run nice on 87.
2. Intake would need a milled spacer to make the transition from round to rectangle.
3. Headers would need the flange cut off and a new one made and welded on.
4. I'd need to sell the extra head

Even though I can do all that in-house and value my time at zero that seems like a lot of unnecessary work when the 95cc Speedmaster head, even before any promotional price costs $100 less per head, has none of those problems and will have no problem supporting whatever anemic power I want to make.

I figured I'd ask here since I have pretty much zero background knowledge when it comes to the options for aftermarket 460 heads.

 

What heads are they?
I bought a Speedmaster head just for the weight savings. It was less than $300 shipped, on sale.
I'm sure that the better heads will make more power, but that's not what you're after.
I might be interested in one and splitting the cost if they are something I can use for my bigger, second engine.

Let me know what you find out.

Bruce

 

I thought I had mentioned it in my comment but they're B460s which per my research is the same as an A460 but with a smaller intake port.

https://www.racingjunk.com/heads/184336429/ford-cylinder-heads-p-n-m6049b460.html

 

Those would not be for me. Chambers too small. Like you said, way more than you need, in work, money and power.

 

I would also pass on those heads. I bought an A460 for mine. It has the same issues with intake and exhaust fitment. It has way more flow capabilities than I need and has (my opinion) created quite a mismatch on my motor. The big heads need a big cam and all the associated parts. That just isn't what most of us are after. There are a couple racing guys on here that may benefit from them, but even for my intended usage it is just too much. I think one of the racers here is even using the bigger C460 head.

One more thing to consider. IF you make an intake adapter that pushes the intake out and away from the block further it will create interference with the distributor which currently fits into a little notch in the factory intake. Move that notch further away from the block and the dizzy no longer fits.

I have no 1st hand knowledge of the Speedmaster head. I had read some bad reviews on it, but I think it was on pre-assembled heads. There were valve sealing issues. If your buying a bare head and doing your own valve and spring fitment your probably good. If I was buying a complete head that used the stock intake and exhaust I would look at the Edelbrock #60669 Performer RPM. (double check that # for fitment. others use the CJ porting)

 

I am thinking a B460 head would be a great choice for one of these engines. It is a smaller port, torque head to the A460. I have used them on trucks. Other then the raised ports should work well.
Then I clicked on the link, that is not a B460 head I have used. If you look the seller is also selling a set of C460 heads, I think he may have his pictures miss matched to what he has. The B heads I have used had large chambers, looked just like a A head with really small ports. The seller does not show the ports on either pictures, so I don't know, but the chambers in his C460 pictures look like the ones on my B460 heads, along with the same rocker stud set up. And his B pictures show 18 bolt heads with shaft rockers.