mercruiser 120 in Starcraft

[idyltimelg]

I will try again. Surely someone on the forum can help me out with performance figures and fuel consumption for an 18' aluminum (Super Sport or Holiday) using a Merc. 120 I/O. I have read general statements that the 120 is a dog, and others that the 120 is a bullet-proof proven performer that is very fuel efficient. Thanks for any assistance.

 

[SpinnerBait_Nut]

Re: mercruiser 120 in Starcraft

Let me get this to the Mercruiser/Volvo/OMC I/O or Inboard forum for some answers.

 

[Bondo]

Re: mercruiser 120 in Starcraft

I have read general statements that the 120 is a dog,

Ayuh,.....
In an 18" starcraft aluminum hull,.... It'll be rather Snappy,......
Til you load in Mom, Aunt Ruth,+ then try to pull your 2 over weight nephews on Skis,.......
Then it'll be a Dog........
In a 21' copy of that hull,.... It'd Struggling most the time........

and others that the 120 is a bullet-proof proven performer that is very fuel efficient.

Ayuh,......
That's Very True,........ It's been making 120hp for about 50 years now,.......
And,.....
As Any Boat,.....
Fuel Efficiency is Directly related to the position,+ motion of the Capt.'s Right-hand..............

 

[idyltimelg]

Re: mercruiser 120 in Starcraft

Bond-o

Thanks for the reply. I saw your post in Marineengines.com where you referenced your Islander, so I will infer that you have first hand experience with the 120. I posted twice in the Starcraft forum hoping that someone with the 18' hull would reply, but no dice. I bought the Super Sport to have a small boat that I could actually afford to run, as my large boat gets about 1/2-3/4 miles per gal. I know it was a gamble to purchase this old boat; even though it only has 190 hours, it has sat up for many years (inside), so it could have many time-related issues. However, it starts right up and shifts (on earmuffs) smoothly. The oil pressure is not what I would like(20-35 lbs), but the oil that is in it looks mighty thin, like maybe 10-30 syn. I am hoping with some SeaFoam followed by the proper 40w oil and some use, any potentially hung up rings will free and all will be ok. If not, the investment was relatively minor at $750 for a boat that seems to have all of its hull integrity, hard floors and a decent interior, on a nice little galvanized trailer. Only Spring will tell.

 

[Bondo]

Re: mercruiser 120 in Starcraft

Ayuh,.....

my Islander had the 3.0l, 140hp when I bought it,.....
And,....
It actually performed quite nicely,.....
But,......
Being the Wrench-head that I am,...... The 4.3LX was a given.......

That SS should give your Good Service,......... Good Luck........
'ell,...... Just parting it out would probably Triple or More your investment..........

 

[DJ]

Re: mercruiser 120 in Starcraft

I have operated a 1976 SS 18' with the 120. It performs about to the equivelant of a 90 HP outboard.

Speeds in the mid to high thirties with a moderate load. The fuel economy is better than an outboard. About 1/3 better.

For $750, you really can't go too wrong. You'll need to do some maintenance.

1. Water pump.

2. Gear lube.

3. Probably exhaust riser, maybe a manifold.

4. Pull the drive and address the Gimbal and perform an alignment.

None of the above are real expensive other than maybe the manifold and riser.

 

[idyltimelg]

Re: mercruiser 120 in Starcraft

DJ-

Thanks for the reply. That is exactly what I was trying to find out. I figured about 35 mph and probably 6-8 gph. Generally it is just me and my wife, w/4 people being a max. anticipated load. I know it is premature, since I haven't run the thing yet, but do you have any opinion regarding Smart Tabs on that hull?

I have already scheduled a water pump replacement and gear lube change. The gimbal is free, lubed and easy to turn by hand and by wheel, so I think I lucked out there. Now that I am writing this, it occurs to me that you were probably referring to the gimbal bearing, and you are right, I need to check that out.

 

[DJ]

Re: mercruiser 120 in Starcraft

Smart Tabs probably would not hurt anything but that hull planes very easily.

I would do some testing first. If you have an issue, then you can look at solutions.

Yes, I meant the gimbal bearing.

Don't forget about the manifold/riser.

 

[95yj]

Re: mercruiser 120 in Starcraft

I had a brand new 1981 19' Citation cuddy runnabout with a 120 Merc in it. It performed just fine and didn't kill me at the gas pump. I could get the boat up to around 38mph with just myself in it, could have 4 people aboard and still get a water skier up out of the water without any problem. With 6 people on board, I had to have a few go forward to get her on plane, but once it was there, it would pull just fine. You won't win any races with the motor, but I had no complaints at all about it in a fairly light boat.

 

[manofprawnz]

Re: mercruiser 120 in Starcraft

Had the same boat and motor for 8 years, great combination, solid hull, takes a beating, no engine issues. It went quite well with 4 aboard, fuel economy was decent. It lived in a marina so not sure how it trailered, can't go wrong at that price, I would have bought it.

 

[idyltimelg]

Re: mercruiser 120 in Starcraft

Again, thanks for the replies. When you are used to cruising 15 knots at .6 mpg on a good day, almost anything else looks fast and fuel efficient.

 

[dwindle]

Re: mercruiser 120 in Starcraft

Hi
I have a 120 in my islander 221 from 1986, hooked up to an alpha one, and it seems really good after one full year of fishing and socializing, even though I suspect that the boat has been "run hard and put up wet" many times. Sure is good on fuel, that I will say. Cheers and good luck