120 140 switchout

[starcrafter65]

Guys,

Simple question - I have a 1968 Starcraft Holiday - came with the 2.5 Liter 120 HP engine. The owner told me the compression was all 135+. Well it is more like 90-90-60-30. (He also told me the wheel bearings were good but that is a whole 'nother story).

Anyway - out with the old in with the new. Going to get a 3.0 liter motor - have a line on some late 80's models.

Here is my question. Does the 3.0 have the same mate-up with the outdrive as the 2.5? Does a late 80's have the same mate up as a 60's outdrive?
Are the motor mounts the same? Any other issues I should look for?

Thanks,

Clark

 

[Fordiesel69]

Re: 120 140 switchout

C'mon man, where's your sense of adventure? Go for an L6 165HP.

 

[starcrafter65]

Re: 120 140 switchout

C'mon man, where's your sense of adventure? Go for an L6 165HP.

Well - I guess - same question with the the 165!!

 

[Fordiesel69]

Re: 120 140 switchout

I actually want to know the same. I don;t know myself! I have the whimpy 120HP with good compression, and would really like the L6.

 

[bigskiohio]

Re: 120 140 switchout

should just swap out , three mounting points exhaust might be a little different, cables, but should be no big problems for the 3.0 , the i6 would not be worth the work and parts in my opinion.

 

[starcrafter65]

Re: 120 140 switchout

should just swap out , three mounting points exhaust might be a little different, cables, but should be no big problems for the 3.0 , the i6 would not be worth the work and parts in my opinion.

Yes - thanks - I got the "book" and it seems pretty simple - the hull only weighs - what 1200 pounds so it should go pretty good with a solid 140...

going to tinstock?

 

[bigskiohio]

Re: 120 140 switchout

*
12 3/4" late model fly wheel- This flywheel is needed if you are replacing a 2.5L or 3.0L engine from a pre 1990 boat/engine. Pre 1990 fly wheels (which are 12 3/4") will not fit, bolt on, or work on post 1990 3.0L engines- the crank bolt pattern is different. The 14" fly wheel that comes with the engine will not work because it is too large for the pre-1990 bell housing AND the starter will not work with the 14" fly wheel- you need to purchase a late model 12 3/4" fly wheel which Michigan Motorz carries for $149. If your existing 3.0L engine is 1990 and later, then you do NOT need this fly wheel.
*
Engine coupler- This coupler is needed for pre-1985 Mercuiser applications and pre-1990 OMC applications. Michigan Motorz carries this coupler for $149. If your existing 3.0L engine is 1990 and later, then you do NOT need this coupler.

layed off so no tinstock for me.

 

[starcrafter65]

Re: 120 140 switchout

Actually just checked the motor out 155 psi all 4 cylinders - clean oil. It has a small drip from the water jacket which had been fixed but then gave out - so that needs to be fixed again. The guy ran for two years with this drip - then wanted to sell the boat and didn't want to sell it with a drip - so he swapped motors out.

The motor is complete - it is a 1989 3.0 complete with motor mounts- it is going in a 1968 Holiday - so I assume I leapfrog over flywheel starter etc.

I will have to check the coupler.

The other thing I noticed is that the wiring harness plug has a different pattern - well if that is the only issue then not doing too bad.

Thanks - if you have any other input go ahead!

$300 bucks

Clark

 

[myoldboat2]

Re: 120 140 switchout

I'd like to hear more about the L6. A while back I asked if there was a more powerful replacement for my Merc 140 engine and was told "not really".

 

[Fishermark]

Re: 120 140 switchout

I am in the process of replacing the 3 liter with an inline six. Fairly easy swap if you have the room up front.

 

[myoldboat2]

Re: 120 140 switchout

Fishermark, do you have pictures you could post? Maybe start a new thread if starcrafter65 won't be going that route. Thanks.

How much did you pay for the inline 6? Is it as reliable as the inline 4 Merc 140?

 

[Bondo]

Re: 120 140 switchout

How much did you pay for the inline 6? Is it as reliable as the inline 4 Merc 140?

Ayuh,.... It's the Same motor with 2 more Holes,... Fine reliable motor...

 

[Fishermark]

Re: 120 140 switchout

Fishermark, do you have pictures you could post? Maybe start a new thread if starcrafter65 won't be going that route. Thanks.

How much did you pay for the inline 6? Is it as reliable as the inline 4 Merc 140?

Probably is best to start a new thread - and yes, I can take and post a few pics. Like Bondo says - very basic, simple, dependable engine.

 

[myoldboat2]

Re: 120 140 switchout

I'll watch for the new thread. Question:

4 holes make 120 or 140 hp, so 30 or 35 hp per cylinder.
So why doesn't a 6 holer of the same engine make 180 to 210 hp?
At 165 hp, that's 27.5 hp per cylinder.

I realize other things can affect power, but what are they in this
specific case?

Also, bigskiohio, why do you say, "the i6 would not be worth the
work and parts in my opinion" ? Is it just that extending the front
mounts forward is a lot of work for the extra 25 hp?

Thanks.

 

[bigskiohio]

Re: 120 140 switchout

25 more hp is problably 5 mph more at wot you dont run ther all the time. less room in boat and there will be other changes front mounts fue line etc. where the 140 is basicly a drop in. for me it would not be worth it. Mine runs around 40 mph so the 140 would run 45 or so plenty fast in a light aluminum boat.