New Project - inline six questions

[Fishermark]

Well, my dad went out and bought a new project for us to work on.

I will be posting quite a few questions over the next few weeks I'm sure.

Here's the brief overview:
Boat - 1970 Sea Ray - 18'

Engine - Mercruiser inline 6 - 250 ci.


First question: Is this what is referred to as the Mercruiser 165? Here's a couple of pictures:

I know serial numbers are preferred... but I haven't gotten far enough into it to see any serial numbers yet.

Second question: If this engine is not rebuildable can I use a truck engine of the same vintage? If so, what are some things to look out for? (I am familiar with small block Chevies and the various differences like one piece rear main, etc, but I'm not real familiar with the inline six engines). Are the heads the same?

I'll start another post with questions on the outdrive.

Thanks in advance!

 

[DJ]

Re: New Project - inline six questions

Yes, you can use a truck engine. Make sure the mounting bosses on the front of the engine are the same. Some automotive blocks had different locations for mounting accesories.

 

[Fishermark]

Re: New Project - inline six questions

Thanks for the quick reply!

 

[starsnstripers]

Re: New Project - inline six questions

Welcome to my world lol. It is a 165hp gm 250 cid. if your gonna use a auto motor make sure that the ear for the two mount bolts are there, fron right corner between oil filter and timing cover. The block i am going to use doesnt but its a rebuilt so im going to fabricate one. The heads are the same but your going to have to put a marine head gasket and brass freeze plugs if it's an auto block. Oh and i think the oil pan from yours or a marine application, Not positive on the pan but i believe the're different. I'm told the truck cams are so close it wont be a noticable difference. good luck !

 

[starsnstripers]

Re: New Project - inline six questions

also clean up and use your rocker cover and valve covers, and a marine alt. / starter. Good Luck

 

[Bondo]

Re: New Project - inline six questions

First question: Is this what is referred to as the Mercruiser 165?

Ayuh,.......... Sometimes...........

There have been 2 Very different 165s,...... You've got the Better 1.......

The Other 1 was a 470.................

 

[Fishermark]

Re: New Project - inline six questions

Thanks Bondo - the other one is the "Frankenstein" motor wasn't it? With the outboard type stator and problem plagued front cam seal, etc?

 

[Bondo]

Re: New Project - inline six questions

Thanks Bondo - the other one is the "Frankenstein" motor wasn't it? With the outboard type stator and problem plagued front cam seal, etc?

Ayuh,........... Exactly.........

Mercruiser's Better Idea,............ That Wasn't................

 

[achris]

Re: New Project - inline six questions

Ayuh,........... Exactly.........

Mercruiser's Better Idea,............ That Wasn't................

Nothing wrong with a well maintained 470!!! Yes the alternator was one of their 'not the brightest' ideas, but I love the water pump and the setup at the front of the engine. If you fit the Ford 'Dove II' head on it, they output close to 250hp!! They just like being maintained with TLC.

The original question -- You have a 160 or 165, in-line 6, 250cid. Solid engine, very difficult to kill. Once you have it running, do yourself a favour and heave the points and put an electronic system in. You'll love it even more.

Chris.............

 

[Fishermark]

Re: New Project - inline six questions

Thanks Chris,
Yep, I fully intend on putting electronic ignition in. We did it years ago in my Dad's other boat - he has the inline 4 120 engine and we put the Pertronix unit in, have never looked back.

On a different note Chris, I read with interest your note about "fixing" the flow of water to the manifold. #3 has me a little confused:

"3. Remove the exhaust elbow and fit a blanking plate over the water galleries between the manifold and the elbow. Has to have a small (1/8") hole for air bleed."

Where exactly does this step come in? Is there more detail you can give me about this? We will be ordering a new manifold and riser/elbow. I take you you would recommend this on a new manifold?

 

[achris]

Re: New Project - inline six questions

The last time I ordered a manifold it came with a water reversing kit included.

 

[flabum]

Re: New Project - inline six questions

Thanks Chris,
Yep, I fully intend on putting electronic ignition in. We did it years ago in my Dad's other boat - he has the inline 4 120 engine and we put the Pertronix unit in, have never looked back.

On a different note Chris, I read with interest your note about "fixing" the flow of water to the manifold. #3 has me a little confused:

"3. Remove the exhaust elbow and fit a blanking plate over the water galleries between the manifold and the elbow. Has to have a small (1/8") hole for air bleed."

Where exactly does this step come in? Is there more detail you can give me about this? We will be ordering a new manifold and riser/elbow. I take you you would recommend this on a new manifold?

They are talking of putting a plate to block off the water flow between the manifold and riser (elbow) You will find it on this page: http://barrmarine.net/wordpress/mercruiser-straight-6-cylinder/

 

[MikDee]

Re: New Project - inline six questions

Hey Fishermark, I rebuilt one of these about 22yrs ago! Great engine. Mine came in a 72' 18.5ft Wellcraft Airslot Bowrider, the motor looked pristine from the outside, but it was siezed. I tried everything, and anything, to free it up because it looked so good, but no luck Basically it was a 250cu in/150hp Chevy Nova, or Chevy truck motor, but with a 2bbl carb (instead of a 1 bbl), and maybe a better cam to deliver 165hp.

I had to drive a couple of pistons out of it, and replace them. I got matching pistons, and all the right parts from Speed Pro, I was amazed at that, through a long defunct auto store chain called "US 1 Auto" I was able to just hone the cylinders well, lap the valves in a bit, clean, & lube it all up, put it back together, and it ran like a champ!

After some break in on the water, with me, & my young daughter in the boat, it was revving to 5k easily, I had no speedo, but I'm guessing it was doing about 40-45. I think the Type 1 drive was 1:5X1 reduction, and I was spinning a 19" pitch prop. But, it was all kinda downhill from there as I put more people in the boat after that run, Not engine wise, But let me Warn you, although the original drive coupling looked pristine, before the summer was over it was about shot! Not knowing that much about I/O's, outdrives, & drive alignment back then, maybe that was an issue, I don't know? it wasn't making any noise? It was a hard learning experience, to say the least

So, let me make a suggestion that you go for a new Drive coupling, and take the time, and make sure, your outdrive is aligned up well.

 

[achris]

Re: New Project - inline six questions

The usual ratio fitted to the in-line 6 was 1.65:1.

And yes, engine alignment is very important.

Chris...........

 

[MikDee]

Re: New Project - inline six questions

The usual ratio fitted to the in-line 6 was 1.65:1.

And yes, engine alignment is very important.

Chris...........

I think the early 70's Type 1 Drive was 1.5:1 gearing for everything but the 4cyl engines.

 

[achris]

Re: New Project - inline six questions

Just checked the Merc Service training handbook.

120/140/2.5L/3.0L - 1.98:1
165 (6 cyl) - 1.65:1
470 (all variants exc 488) - 1.84:1
488 - 1.65:1
earlier 4.3 V6s - 1.84:1
898/200 (305cid) - 1.65:1
Ford V8s - 1.5:1
Most GM small block V8s - 1.5:1
GM big block V8s - some 2.0:1, some 1.5:1

Chris.........

 

[MikDee]

Re: New Project - inline six questions

Your probably right Chris, I seem to remember reading it being 1.5:1 somewhere though? It's been many years since I've needed to know, probably the Haynes, or Clymer, Mercruiser book (that I can't find right now), but we all know how accurate they are

 

[DJ]

Re: New Project - inline six questions

That engine, no matter what you do, doesn't like anything over about 4300 RPM. It complains-loudly over that RPM.

It's a great engine. Prop it to turn a tiny bit over 4300 WOT(very light load) and it will serve you fine.

MerCruiser made/makes an "elephant ear" prop that works well, with that set up. Various pitches are available. The engine delivers gobs of torque at mid range. Overrevving gets you nothing. 4300-tops. I'd start out with a 19" prop pitch. See where that gets you.

Realize that the engine is NO speed demon but it is very reliable.

Good luck. Take care of it and it will run for years.

 

[Bondo]

Re: New Project - inline six questions

On a different note Chris, I read with interest your note about "fixing" the flow of water to the manifold. #3 has me a little confused:

"3. Remove the exhaust elbow and fit a blanking plate over the water galleries between the manifold and the elbow. Has to have a small (1/8") hole for air bleed."

Ayuh,.............
Maybe FreebeTony will stop by,+ let you in on How to build yourself a Full Closed Cooling system for that motor,......

Basically,........
You need the Nipple End-plate that's required in Chris's reverse flow system,+ a Heat Exchanger................

Btw,......... DJ's Right,..... Those ole I-6s would rather Lug than Scream...........

 

[Fishermark]

Re: New Project - inline six questions

I've boated in salt water here in Florida all my life - never have had a closed cooling system. Always thought it would probably be a good idea.... just never have done it. Just flush it every time and replace everything often!!

I'm starting a new thread on timing marks...