Is this motor REALLY a 1978 200hp?

[Raysoncrafter]

Long-time lurker here- and now that I'm an outboard owner at last- I will have some questions for you Merc outboard guys.

I recently bought a boat with what the owner described as a 175 with 200hp markings- he supposedly knew of this before he bought it himself back in the early Eighties. It's described as a 1978 200 with s/n 5364431 on the plate. The external decal of course calls it a Black Max 200.

Since I've learned from this forum that there were no 200hp 2.0's ever built, what physical differences are there on the 2.4 that would separate it from a 2.0 that a newbie could determine? What photos could I take and post to make it easier for the experts to see for themselves?

Thanks in advance- I'm hoping to try and fire this thing up sometime in the next week or so- more questions then.

DaveA

[johnboy 88 vegas]

2 liters and 2.4's will have the bore size stamped on the face of the head near the top.....3 1/8"= 2liter..... 3 3/8"=2.4. Someone still could have swapped the heads from one motor to another.

[MercNuts]

2 liters and 2.4's will have the bore size stamped on the face of the head near the top.....3 1/8"= 2liter..... 3 3/8"=2.4. Someone still could have swapped the heads from one motor to another.

That is not true on V6 Mercs made in the 70's. And back then the heads between the 2.0 and 2.4 did not interchange without doing some changing on the bolt pattern. The bosses for the headbolts on the early engines were on the side of the casting for the cylinder rather than the block as they were done later. Early 2.0s would have a distinctive bolt pattern. I dont remembrer the diameter but if nobody else posts it up tonight I can measure one tomorrow. I think there are other obvious external differences but Im drawing a blank. It is very easy to tell with the exhaust divider plate removed because the 76,7,8 2 liters had that funky shape at the bottom of the powerhead where the 2.4s were rectangular.

[Raysoncrafter]

I've checked the heads with the cowl open as much as possible and I see nothing on the heads as described. Here's some photos of what I did see.

[Raysoncrafter]

The first photo is of the top of the engine as you can tell. The second is of the pad on the base of the left head near the top. The bottom one is the numbers on the midsection. There's a number stamped between the heads at the base of the engine in the back that I cant read unless I remove the cowl. I took a mirror and looked at the tops of the heads- there's a number there along with the Mercury Marine logo, but it's not anything like 3-1/8 etc.

[MercNuts]

It was nice of somebody to put an aluminum flywheel on it for you.

[Capt.Insane-o]

The early 2.0 heads will fit on the early 2.4's, just sayin'.

[b0atguy]

That appears to be a 2.4 block. The dead giveaway is the smooth "ramps" on the top of the block leading to the heads. The 2.0L blocks had a "boss" cutting into the ramp on the top of the block to accept the longer thermostat bolts . The 2.4's did not have the "boss".
I would say you have a 2.4 block, possibily an 81. You can easily tell the HP by looking at the cylinder block on the port side, where the halfs meet approx around where the timing advance stop is. If its a 150, there should be a 5 stamp. If its a 175, it should be a 7 stamp. If its a 200, you should have a 2 stamp. I have several powerheads sitting here, 2.0L and 2.4L. If you need any pictures of anything let me know. I Just checked them, to confirm the numbering.

b0atguy

[pyro]

If you lift straight up on those cowling halves, they will easily lift off, one at a time. Each side has two pins that drop into sockets on the back end. It's really easy.

[WATERWINGS]

I see "81" stamped at he block 1/2's......

[Capt.Insane-o]

It appears as if someone has cut the heads down as much as possible too.

[Raysoncrafter]

This is exciting- I think I got a 2.4 200 after all- here's more photos- what do you guys thinK?

I hope this is the number 2 you're talking about---



You guys think these heads have been machined?



Port side of engine



Guess what else it needs- any suggestions on replacements?

[Raysoncrafter]

This is great- thanks for such good information!

MercNuts, didn't notice the aluminum flywheel- BONUS. Thanks!

Pyro- that was so simple & I didn't even think of it. Thanks for the reminder...

b0atguy- hope the photos confirm what you've been saying. 2.4?

capt insane-o: you still think the heads have been cut?

[TEXAS20225]

its a first generation block with head bolts attached to the sleeves( it looks like)

[TEXAS20225]

prop shafts are plentiful