Mercruiser 165 questions

[cantaris]

I bought a 1971? Reinell 24 ft hardtop cabin cruiser with a GM L6 6cylinder engine. I believe it is the 165. The outdrive says model 120/140 H.P. Does the outdrive model indicat that it is for 120 or 140 hp engine?
The merc 165 is a 250cid engine. Is this combo large enough for a 24 foot boat? I am assuming that everything is original. Engine has no rust on it and cranks over, or at least did. Has a short somewhere. Is it worth rebuilding and keeping in this boat? Or should I think about an upgrade? I plan on using it mostly for fishing and trolling out in the Puget Sound and for going out tuna fishing off the west coast of Washington( 30-100miles). Any thoughts would be welcome. Thanks

 

[dan t.]

Re: Mercruiser 165 questions

first things first ,check the stringers,this machine is old. tap with a small hammer ,a sharp crack noise means much happyness, a dull thud means delamination or ROT. wish you luck ,I think you may need it

 

[cantaris]

Re: Mercruiser 165 questions

Already figured out that the stringers and transom may need replacement. I was just wondering wether or not to put this engine back in and if it is strong enough.

 

[chiefalen]

Re: Mercruiser 165 questions

The motor is a little lite for that size boat.

But if you do change it you will have to change the gearing in the drive.

 

[180shabah]

Re: Mercruiser 165 questions

The motor is a little lite for that size boat.

But if you do change it you will have to change the gearing in the drive.

Depends on how fast he wants it to go.

Also, does it have the correct ratio now? 120/140 = 4cylinder, need to determine if the gears were changed when the drive was replaced.

 

[chiefalen]

Re: Mercruiser 165 questions

I could be wrong, won't be the first time, but the gearing is the same for the 120/140/ L6.

Is probably the original out drive.

You gonna go off shore i strongly recommend you have a kicker motor on board.

10 hp at least.

If it were my boat i would rebuild the motor and drive. Ain't a speed boat, and a very reliable package.

Good luck if you need help just post.

 

[Don S]

Re: Mercruiser 165 questions

GM L6 6cylinder engine. I believe it is the 165. The outdrive says model 120/140 H.P. Does the outdrive model indicat that it is for 120 or 140 hp engine?

Someone put the wrong drive on it. The 165 uses a 1.65: 1 gear ratio, and the 120/140's used a 1.98:1 ratio. the 120/140's were also 4 cylinder engines.
It's possible the gears were changed in the drive to make it 1.65 .

A 165 motor in any 24' boat is too small. Might be ok for trolling around the sound fishing, but I sure wouldn't be taking anything that old and underpowered, 30 to 100 miles off shore.

PS: This is a Mercruiser isn't it?

 

[chiefalen]

Re: Mercruiser 165 questions

That 165 ain't the original motor to that boat.

In my garbage book it don't show the 165 till 1972.

70' and '71 shows a 155.

Don't show a 140 till 73' -Shows the gear 19.20 upper/ lower 15.23 overall 1.61

73' 165 shows upper-21.19 lower 15.23 overall 1.39

Garbage book has been wrong before though.

Maybe like don said they already changed the gear if they put a different drive.

 

[cantaris]

Re: Mercruiser 165 questions

So how do I tell if it has the correct gear ratio?

 

[chiefalen]

Re: Mercruiser 165 questions

You got to count the teeth.

Has to come apart anyway.

 

[Don S]

Re: Mercruiser 165 questions

Pull the spark plugs out of the engine so you can turn it over by hand.
Put the shifter into forward.
Turn the engine by hand in normal direction of rotation (DO NOT BACK UP for this test) till the timing mark comes up to TDC.
Also have someone watching the prop.
Mark the prop so you can tell when it makes ONE FULL REVOLUTION.
Turn the engine by hand in the normal direction of rotation and see how many revolutions of the crankshaft the engine has to turn to turn the prop one full revolution.
Almost 2 full turns indicates a 1.98 ration (notice, almost 2 to 1 ration) would mean that it's for a 4 cylinder motor.
Just a bit more than 1.5 turns would indicate a 1.65 (just over 1.5 turns or 1.5 gear ratio) and the proper ratio for a 165 IL6 Chevy.

If you look at the picture below, you can see the IL6 was used from 63 to 81, in one form or another.

 

[mthieme]

Re: Mercruiser 165 questions

Hey Don, that's cool software!
Would that be the $900 stuff that my local parts guy covets more than the family jewels?
or is it available at a reasonable cost?

 

[chiefalen]

Re: Mercruiser 165 questions

See why i call it a garbage manual.

Way kewl software.

 

[cantaris]

Re: Mercruiser 165 questions

You got to count the teeth.

Has to come apart anyway.

Which gear teeth do I need to count, as there are several in n outdrive?
And how many teeth needs to be there?

 

[Bondo]

Re: Mercruiser 165 questions

Which gear teeth do I need to count, as there are several in n outdrive?

Ayuh,...

Up until quite recently,.. All of the Lower units were 1.65 to 1....
The Final Gear Ratio is determined by the Upper Gear Set....

Btw,....
Counting the rotations like Don explained is a Much Easier way to figure it out....

 

[180shabah]

Re: Mercruiser 165 questions

Count rotations, then figure out what it is closest to:

1.5
1.65
1.85
2.0

 

[chiefalen]

Re: Mercruiser 165 questions

I pulled out the e-basic catalog. Inline six cyl. Page 14.

They list 24-24 tooth gears. 1:65.

Funny part they list 20-24 tooth gears. GM 4 cyl. 1:98.

 

[180shabah]

Re: Mercruiser 165 questions

They list 24-24 tooth gears. 1:65.

Funny part they list 20-24 tooth gears. GM 4 cyl. 1:98.

What's the funny part?

20-24 = 1.2:1 ratio multiply that by the 1.65 ratio of the lower unit gears and you get 1.98:1 - which is the final ratio for the 4 cylinders.

 

[cantaris]

Re: Mercruiser 165 questions

So What would happen if I was to run this combo, if the the gear ratio is 1.98:1?. Out drive SN is 4526761 if this helps

 

[chiefalen]

Re: Mercruiser 165 questions

Funny, in how thats not what they sent my friend. He has a 93' 3.0 gen2. We did his drive at the same time i was going thru my problems.

What they sent my friend was less 2-3 teeth. He bought the 350.00 gear set from them. After market.

I was thinking about his drive and posting here.

"Funny" did not pertain to this post.

Just wanted to let the op know how many teeth were in each drive.