Newbie to V6 mercs

I just picked up 3 parts engines, enough to build 2 good ones... but 2 of them are basket cases and I'm trying to figure out what's what?
First off, can someone explain to me the difference from XR1/XR2 and regular engines?
The first engine is complete, not running, but not seized.
It's a 200 extra long shaft (25" mid) with a one piece cowl. The numbers on the tag on the transom clamp are all erased.

The other 2 are 20" mids.
numbers are A933604 and 0D043980




And the cowls


I'd like to have an idea of what year they are and what were the major differences.
Oh yeah, and are these 2.5 liter engines?
Thanks in advance for any info.
PT

Re: Newbie to V6 mercs

http://www.maxrules.com/models/Merc_model_files/175-300.html

Check here for info on your serial numbers. My memory is a little foggy, but your 1750 case looks older, and in those years I think the 175 was a 2.0L? Then the 200's were the 2.5 but dropped down to the 2.4 sometime in the late 80's and got rid of the chrome lined cylinder walls which make them a PITA to bore and rebuilt IIRC.

Re: Newbie to V6 mercs

So out of the 2 basket cases one would be an '86 or '87 and the other a '91... I'm guessing that would be the oil injected 150.
Still doesn't give me much to go on

Re: Newbie to V6 mercs

Thinking about it more, I seem to think it was the 80's engines that were the 2.4's with the chrome bores and the late 80's or early 90's they switched to the conventional bores 2.5. I think all or most of your bolt on stuff will swap. I know there are other members with much better info on this stuff that me.

Re: Newbie to V6 mercs

Between the 150 and the 175 everything looks like it could swap but there are some differences... the shape of the heads, one set of pistons has thin connecting rods and two rings, the other set has thicker rods (same size journals) and three rings.
I only have the one block and it has steel sleeves.
The two cranks are identical and so are the crank covers.
I only have the one lower that came with the basket cases and it's very different than the one on the 200...

I really wish someone that knows more would chime in...

Re: Newbie to V6 mercs

The 175 is either a 1976 or 77. the 175 is the one with the odd looking gearcase, I know that case was used 76-78. The 3 ring pistons were superceeded by the 2 ring design, so the 3 ring pistons are from the 175. The 200s, by the cowl look like 1986 - 88. The XR1/XR2/XR4 engines were engines that has different torque/horsepower curves than the standard engines of the same rated hp. I know that one of the 150 XR2 or XR4, it's been 26 years so I might not get it all correct, had different exhaust tuning, porting, and reeds than the standard 150. It had greater oumph in the midrange and could out accellerate the standard 150, but was less fuel efficient. It wasn't a 165hp in disguise, it made 150 but it had to turn an extra 500 rpm to do it because it had less torque at high speed than the standard 150

Re: Newbie to V6 mercs

Ok, thanks Jimmbo.
Can anybody tell me what the bore and stroke were on the 2.0, 2.4 and 2.5
I just checked the compression on the 200 tonight, 115-120psi on the top 4 and 60-70 psi on the bottom 2 holes...
I'm wondering if the pistons from the 150 or 175 will fit in the 200.

Re: Newbie to V6 mercs

Can anybody tell me what the bore and stroke were on the 2.0, 2.4 and 2.5

Click to expand...

They are all the same stroke(2.650) only the bore size is different...2.0 is 3.125, 2.4 is 3.375 and 2,5 is 3.501, you need not worry as you have no 2.5 items.....

I just checked the compression on the 200 tonight, 115-120psi on the top 4 and 60-70 psi on the bottom 2 holes...

Click to expand...

Not good.......

I'm wondering if the pistons from the 150 or 175 will fit in the 200.

Click to expand...

Nope...your 150 and 175 are 2.0 motors and the 200 is a 2.4 a 1989 model as they did not make a 1 piece stock cowling in 1988.

I only have the one block and it has steel sleeves.

Click to expand...

That likely a 2.0 (measure bore) and if its the late model it will have a boss and hole for the oil pump, if not its the old 175 and the exhaust on bottom of block is different along with heads as the bolt patterns are different. Your picture of the 200 has the 175 midsection beside it as I can seen the "D" shaped exhaust ports...
The Xr2 motors where just stock motors with a 2.4 tuner, divider plate, different reed stop, louvers on cowl and a advance box, nothing special about porting. The Xr4 is a detuned 200hp 2.4 with vertical reed setup like the 2.0 motors, steel sleeves and porting is not as high as a 200hp due to the restricted breathing and usually came with the small 4-1/4 gearcase in 1.78 ratio

Re: Newbie to V6 mercs

Thanks Faz. I went out and measured the bore, it's a 2.0
No oil pump casting that I can see... but the exhaust ports are square and match the 150's mid.
So I have parts from more motors of different years than I first thought.

Re: Newbie to V6 mercs

Took the heads off the 200 today. It's a 2.4 with chromed jugs, and they're all in ruff shape, pitting in 4 and pitting and scoring in the other 2.
No quick fix here...

Re: Newbie to V6 mercs

The chrome bores are neither cheap nor easy to fix. If the 200 is otherwise complete, what I would do is part out the other two motor and use the funds to buy a 2.5 block for the 200. Perhaps someone else can chime in but I think the 2.4 parts will all bolt onto the 2.5 block. This way you could get yourself a set of new pistons and rebuild the powerhead.

Re: Newbie to V6 mercs

I think that's the way I'm gonna go...
What range HP's and what year engines would I have to look for to get a compatible 2.5 block?

Re: Newbie to V6 mercs

Hopefully faztbullet will chime in again but I think any of the 90's V6 blocks will be 2.5's. Or was the 2.0 still around in the 150hp? Not sure if there's any difference in the actual 2.5 blocks themselves but I think for your uses it would be interchangeable.

Re: Newbie to V6 mercs

I think the 2.4 parts will all bolt onto the 2.5 block.

Click to expand...

Sorry but no as 2.5 uses a wider divider plate and head bolt pattern. the internals(crank/rods) will work along with electrical. The 2.5 did not come out till 1991..