1974 1500 mercury

[1974 allison]

just picked up a 1974 mercury 1500 long shaft, not a j block, it has a very long pointed bullet on the gear case, no low water pickup, looks to be part of lower unit , not added on, never seen one like it before, is it original? anyone have any insight ?

[evinrudejohnson]

Post a picture

[1974 allison]

finallly figured out how to upload pictures

[milkdud]

Its added on, and mostly un-needed for the inline 6 gear case. They blend those in very well when they put them on.

[milkdud]

If you look at your block where the J would be stamped. Is there a C with a circle around it? Supposedly the Circle C blocks had squared out exhaust ports from the factory. I believe they came on 1974 long shafts. Take a look and see if you get time. I have one but have not tore it down yet.

[wired247]

If you look at your block where the J would be stamped. Is there a C with a circle around it? Supposedly the Circle C blocks had squared out exhaust ports from the factory. I believe they came on 1974 long shafts. Take a look and see if you get time. I have one but have not tore it down yet.


I fought a couple of those circle C blocks and they about drove me crazy. Terrible low end torque. Ran great on the top end but down low it was a constant struggle. Mine were '73 blocks

[1974 allison]

thanks for the insight, will check for the circle c this weekend,,, going to check compresion & spark to find out if I have a runner or a parts engine

[gmjim]

Is the circle c cast or stamped? I have a '73 & two '74 blocks here, I think at least one has the cast 'c' on it.....

[milkdud]

I believe cast.

[wired247]

It is cast in. The "circle" is a raised pad and the "C" is cast in. Ports are higher on those blocks than the later blocks. Mercury apparently and rightly so had a lot of complaints about low end torque with the early 1500's and subsequently lowered the ports. I couldnt get mine on plane with anything more than a 19 pitch prop and that was with a couple of different circle C's and all kinds of swearing, carb and timing adjusting and overall grouchiness.

[gmjim]

I checked out the blocks I have here and one is def. a circle c, cast no. 852-5033, I see no visually discernible difference to the 1974 (cast 852-5264) block next to it as far as exhaust ports go, but I can say they are both quite noticeably larger and higher than the 1978/9ish 140 block that is sitting with them.......the third early block I have is my running motor so hard to check it..... Let me know how/where to measure or photo if needed!

[milkdud]

GMJIM,

The exhaust ports on the Circle C. Are they round or D shaped? Attached is a Circle C block that was shown last year by a member here.
C

[wired247]

Heres a couple from one of mine.Also note the one year only water cooled fuel pump boss. ....

https://imageshack.com/i/i320120515165405j

https://imageshack.com/i/4820120515165331j

https://imageshack.com/i/2s20120515165302j

[gmjim]

yes, they both look very familiar/similar to mine, mine also has the extra cooling for fuel pump. The best i can describe it is the sleeves are matched perfectly to the ports in the block, as opposed to the 140 block which has a very discernable step from the sleeve to the block casting....i also noticed that this is the same casting number as the T2X block that Arne has posted pictures of previously.
Hey wired, those ports are very clean, was that motor super rich or just fresh enough that it hasn't carboned up?
How was the top end on the '73? did it feel any faster than a later 150??

[wired247]

yes, they both look very familiar/similar to mine, mine also has the extra cooling for fuel pump. The best i can describe it is the sleeves are matched perfectly to the ports in the block, as opposed to the 140 block which has a very discernable step from the sleeve to the block casting....i also noticed that this is the same casting number as the T2X block that Arne has posted pictures of previously.
Hey wired, those ports are very clean, was that motor super rich or just fresh enough that it hasn't carboned up?
How was the top end on the '73? did it feel any faster than a later 150??

That was a 40 year ish year old motor when I opened it up. Take a look at the piston behind the exhaust ports. Not looking so good. That 1500 ran like crap even after it was rebuilt. WAY too soft on the bottom end. Once it was up on plane and past 20 MPH it sounded like an abused chain saw and ran up into the mid 60's but the 140 Johnson that was on there before that would do the same thing except for the running like the crap down low part.

[1974 allison]

Wired, what was the hull style, and weight of the boat that the circle-c was ran on?

[wired247]

Wired, what was the hull style, and weight of the boat that the circle-c was ran on?

It was on a '81 Checkmate Enticer . 1200 lbs or so with motor. It would plane fine with a 19 pitch, More or less OK if I shifted weight to the front with a 21 pitch and usually not at all with a 23 pitch. Once it did plane it would scoot right up into the 60's. Sounded just like a Husqvarna.


https://www.youtube.com/watch?v=SrQIXLjy3-g

[1974 allison]

Thanks wired,,,,, was thinking that this may go on my 1974 r16 Allison,around 900 lbs, have ran a 78 mercury 800 with a 22 pitch laser, would jump up on plane great and would run around 45-48, with some better set up I'm sure it could of been in the 50s. were you running vented props on the checkmate? Just looking ahead for solutions to a possable problem,,,,,WOW,,,, need to get this project done over the winter, so I can have some fun next summer

[1974 allison]

it is a 0 C block, has the fuel pump cooling. Going to check compression and spark later today.