TOPIC: 1968 Convair

Hello all, I have a 1968 Convair with a 4 cylender gm motor, can't seem to find any info on this boat. looing for max rpm and normal rpm. also would like to know oil requirements for the engine and the outdrive. any info would be awsome.

stew0576,

WELCOME ABOARD.

Your I/O engine is LIKELY a 120 HP 4-cylinder Industrial Quality (usually installed in FORKLIFTS. - It is NOT a Chevy II engine, despite what some people say.) 153 cubic inch displacement engine (over the last 40+ years, the engine may have been changed. - It pays to be SURE what you actually have!) that has been "marineized". - The 120 GM engine is TOUGH, EASY to maintain & cheaper than most I/O engines to run.
(It uses 4 quarts of 25W40, according to the manual. It has been my experience that a QUALITY 20W40 SD oil is fine for the 120 & 140HP.)

Presuming that your outdrive is the ORIGINAL, it is a MERCRUISER model II.

Fuel: These engines are a nearly 60 year-old design. They should NOT be run with gasoline/alcohol blends.
(You can find "non-alcohol-blended gas, if you "look around." -For example, there are any number of service stations that sell NON-alcohol gasoline in the San Antonio metropolitan area.).

You should also run "lead substitute" additive in your gas. - MOST of these engines run OK on a QUALITY "mid-grade" pump gasoline.
(I never ran PREMIUM in mine.)

Unsolicited/free advice (I presume that you know how much "free advice" is generally worth. = CHUCKLE): Get yourself a SELOC manual #3200, if you don't already have one. - I paid 12.oo for mine, used, on amazon.com.

SORRY. I don't know anything about Convair boats. - I've never even seen one, except in photos.

I hope these comments have been a help to you.

yours, satx

That helps, i appreciate your advice, i've looked into unmixed gas in my area, have to travel a long ways or pay marina prices, can i use the mercruser treatment? it says it will keep the ethenol from doing damage? or should i just pay marina prices?

stew0576,

I know ZILCH about the "Mercruiser treatment" - thus I cannot comment intelligently on it.
IF I still had my old boat & there was NO "un-mixed gas" nearby, I would buy a barrel or two of UN-mixed gas, put fuel stabilizer in them & make my old engine "happy".
(FYI, I'm too much of a cheapskate to pay "marina" prices.)

yours, satx

stew0576,

BTW, "back in the day", my local EXXON distributer offered to DELIVER barrels of gas to me, as I bought so much fuel, when I was "commercial trotlining".
IF you have an "independent distributer" nearby you might ask if they "deliver" - Never hurts to ask, as the worst that they can say is, "NO".

yours, satx

I understand that, as a husband and a father of three with one more on the way I have to find ways to reduce costs whenever possible, going to have to try mixed for the moment I guess, will see what I can figure out for stocking up on unmixed, I like the way you think

I understand that, as a husband and a father of three with one more on the way I have to find ways to reduce costs whenever possible, going to have to try mixed for the moment I guess, will see what I can figure out for stocking up on unmixed, I like the way you think

ohh, just a heads up, I traded a used ipad for my boat, the guy just wanted to get rid of it, it ran backwards, when you pushed forwards it went back and vise versa, I switched the shift wires around and it works perfect

stew0576,

LUCKY YOU!

yours, satx

Welcome aboard.

If that outdrive is electric shift, then you have an OMC I/O, not a MerCruiser as was assumed above.

Also, MerCruiser never used a #2 drive with the 124/140/160 engines. It would be a #1 drive, but that is not relevant at this point.

Also, the 153 CID (110/120/2.5L models) engine was indeed used in Chevy 2 cars. It was based on the bore & stroke of the 230 CID inline 6. Check about 1963 to 1966 timeframe & you will find it used. The 181 CID (140/3.0/3.0LX models) was not used in any autos in this country that I am aware of. It is not based on any GM 6 cyl variant. The math comes out to 271 CID. It was indeed its own oddity but yes, it does look externally like a 153/2.5L block. As far as I know it was strickly industrial/marine but perhaps in foreign countries it was used on the roads.

As for fuel treatment, it is best to find a fuel additive for valve wear if possible. I am not aware of MerCruier or OMC marketing any but it can typically be found at auto parts stores. Marine dealers may also carry it.

The sharp entry of the keel suggests MFG boats for the manufacturer to me.

Jim

i will get pics tonight of the boat, engine and outdrive, thanks for the input, my plan is to use it for the summer then restore it this winter, going to be a fun project to do with my sons.

stew0576; jimandros; All,

FWIW, my CHILTON"S GUIDE # 3200 states on page 440 that the CORRECT Mercruiser outdrive for the 1968, 120HP GM, 4-cylinder was the Model I.
(I mis-typed the data & didn't catch it. = SORRY.)

As to the Industrial engine/Chevy II controversy, I was told by the late Marlin Manjos of Marlin's Marine Services (Marlin was factory-trained by Mercury long ago & forgot more about Mercury motors than I will ever know.) that the 153CI Mercruiser is NOT the same block as the old Chevy II block as it was "built heavier in every way", though it has the same Cubic Inch displacement.
Additionally, the pistons, connecting rods, crankshaft, bearings, valves, gaskets and virtually every other component, except the marine manifolds, generator & starter, are the same as the Industrial Engine.

yours, satx

nice, sounds like a solid engine, any idea where to get repair parts, took it out today after cleaning carbs and it ran a little better at first but then started acting up again, think I need to rebuild the carbs on it. Not overly experienced with carbs but I'm pretty handy with a wrench

stew0576,

NAPA Auto Stores sell marine parts for most popular marine engines, including the older outboard motors.
(Around here O'Reilly's Auto Parts sells them too.)

note: I work for NEITHER commercial company.)

yours, satx