Question on an inline

[specboatops]

Hi guy's, hope someone can help me out.
On my 1500xs Iwas told to move the water discharge fitting from the middle of the head(actually to block it off) and move it up around the #1 plug, I was told this would help keep #1 cooler as this is usually the cause of many problems with the old inline motors,I've looked around on this site before posting to see if I could find anything but no luck!
Any help in this matter is appreciated,or any other hepful hints with these old motors.

Chris

[lightchop]

I was told through this board to do the same thing. run the tale tail off the top of block to prevent an air pocket from forming. The current block im using on my 1500xs lower is a standard 1500, and has no facilities on the top fer this mod. (not shure about about adding one). but i looked at the original xs block, and it has castings that can be machined fer this.

[specboatops]

....is just what you stated I drilled out a spot on top of #1 and pluged the one around the #3 hole,re plumed the (actually I bought a new piece)water line to it , it seems to run fine, though I did do this at the end of my boating year , October of 2004,so I don't have much run time on it.
I did notice that when I turn engine off,I don't see as much water continue to drain,but I suppose this is due to the higher posistioning of the piss tube.

Chris

[Raceman]

The XS blocks are the exact same castings as the std 1500 of the same time period. As far as the block itself, only the port timing is different, and that's a machining process.

[sho305]

I've read both do it and not to bother. There are some great inline posts on here about that stuff. Mostly run good gas/oil and not too much timing, and keep a good impellor in there. Oh, and have a good clean working fuel system.

Use the search function with "inline" and maybe "1500" etc., look for longer posts. Some are a couple years old and the searcher does not always like to look back that far. They are there, just takes some stirring to find them.

[Dave S]

The blocks with the top water outlet is the better block. It has different water passeges that cool the exhaust side better. I think the blocks with bolts only on the front halve, not nuts and bolts are the block that makes the change. They got better as the years went on.

[Bruster]

The old 3 cylinder 49 ci Mercs have suffered a pretty bad rap 'cause they would routinely fry the top cylinder. The fix was/is to move the discharge to the top of the block. Guess what? The 3 cylinder is simply half of a 99 ci inline 6. I think this mod has positive merits.

[Raceman]

It might, and some people who have a lot of inline experience believe in it, BUT, I've never cooked #1, so haven't thought it necessary. One thing about it though, with no downside to the mod, there's no reason not to.

[CrayzKirk]

Here are a couple of pics of a late model with telltale at top and how I did it on a trashed block. Used a pipe tap and pipe dope with plastic fitting.

Kirk S.

[Jeff_G]

All of the inline blocks from 1973 on had the exact same water passages with the exception of I believe the 1973 (don't remember the exact year) and prior had a service bulletin to drill and insert a larger water tube in the bottom of the exhaust side of the block. Since the mid 70's I haven't seen any blocks that either weren't modified or factory changed. You can see this opening which is about 1/4" at the bottom of the block going up at an angle towards the inner water cover on the exhaust side.
That being said, that is the only water passage difference. The nut and bolt and through bolt blocks were the same.
The reasoning behind the change on the tell-tale is the inlines fill from the bottom. If a motor is running a little on the hot side the earlier motors could and did form a steam pocket that surrounded the #1 cylinder. The later ADI motors had a running change that moved the tell-tale to the top of the block. You can do this on earlier models by drilling and tapping the block. It is thin material so take your time. Use a 1/8 pipe tap and right angle fitting. either block off the hole on the back of the water jacket or install a water pressure guage there.
In fact the earliest inlines had a take off for the tell-tale on the lower side of the water jacket on the exhaust side, later moved to the rear water cover and later to the top of the block.
A simple and effective way to prevent a steam pocket and ensure water is circulating all the way to the top of the block.

[Dave S]

Hey Jeff, your rite about that hole on the bottom. That is the difference between the nut blocks and the later bolt blocks. The bolt blocks had that lower hole that cooled the exhaust side better.The cool water short changed the exhust plate warm up feature. Just what I have see in my years.The T2x block was older style but they drilled a hole at the top to bleed the steam out of that area.

[specboatops]

When I first purchased this motor it had a bigger piss tube coming out of motor,it seemed to have more water coming out but not at the pressure you would see on the stock set up, I replaced it back to the oem style,is there i better way to go??????

Chris

[xskid]

1977 was the first year for bolts threaded into block. but still had tube coming out of water jacket. 1978 was first year for telltale coming out of the top of block, which i beleive is better. as far as steam building up at top of block, i think as long as you dont troll around too long under 1000rpms, i think you might be o.k.