Buying a motor for parts?? Good idea??

Randy W.

Seaman
Joined
Dec 12, 2006
Messages
74
I'm thinking about picking up a mid-70's 105hp for parts (very cheap). The current motor I'm working on is a 1977 75hp. Would there be many interchangeable parts? Both are 3 cylinder---wondering about ignition parts, lower unit, starter, etc. Just wondering if others have had successes or more hassles with this idea? I haven't really gotten into my 75hp project, so common sense would dictate finding out what I might need first???? But it's soooooooooo cheap...and lost most of my common sense years ago!
 

wilgil

Cadet
Joined
Jun 16, 2008
Messages
25
Re: Buying a motor for parts?? Good idea??

I think you will find quite a few bits of value - the starter motor, CDI and I THINK the pistons too - the clymer manual states the same bore and stroke anyways. Frank will be able to confirm. I have just swapped the lower unit from a spare 75 over to my 105 because it had a better water pump housing, so you're good there too. I think the props. are different, but in the compatibility chart the 75 prop can be used for the 105. I don't notice any real difference. What's so wrong with the 105 that you can't get it going? I love my old 105! The 105 is a 4 cylinder by the way, not a 3 - sure it's a 105?

By they way - I have a few spares for keeping on the water as cheaply as possible - apart from the 105 on my boat I have - 75, 85, 90, 90, 105, 120, 135 - I should be ok for a while yet!
 

mthieme

Captain
Joined
Oct 6, 2007
Messages
3,270
Re: Buying a motor for parts?? Good idea??

While I can't elaborate intelligently about your specific motors, I can tell you that I have purchased motors in the past strictly as a parts motor. I've always had Mercs. I happened across a '78 402 Merc last season for $100. It seems one of the local hoodlums was trying to scare up bail money.:) It had a SS prop on it, that alone was worth it. If you have a place out of the way to store it, this is not a bad idea.
After getting it home and checking it out, I have hopes to hear it run this spring! It will be one big spare then!!!
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: Buying a motor for parts?? Good idea??

The 105 and the 75 will use the same starter, same alternator stator and flywheel. The Motorola ignition is swappable, however even though the distributor body is the same, the center shaft rotor, and cam (a permanent assembly) can not be swapped because one is three lobed and one is four. If one is an electronic distributor and the other is a points signaling, the electric eye is swappable IF you get a center shaft with a shutter to match which engine you are using it in. Lower units, while they may look different are completely interchangeable, both externally and internally.
Reeds and Vee blocks are the same except the 105 has four of them. Fuel pump is exactly the same. Carbs are different but if you found a third one for the 105 pair, then you could use three 105 carbs as a set on the 75--do not expect an increase in horsepower though.
Choke solenoid, starter solenoid, bypass covers, pistons and rods: all are the same.

Even the match plate and exhaust down tube are the same.

HOWEVER: if the 105 is anywhere near repairable, IT is the engine to use if your hull is rated that high. The fourth cylinder and extra displacement gives much more torque and you will be happier with it on the hull--especially if you intend skiing.

Just noticed you said both were 3 cylinder engines. The Largest 3 cylinder Chrysler ever made was 90HP. Are you sure that a 105 hood is not sitting on a 3 cylinder engine? 3 Cylinders were 70, 75, 85, and 90. Or di the seller describe it as a 3 cylinder 105? Check the model plate under where the fuel line and control cables enter the engine. The first two or three numbers indicate horsepower.
 

Randy W.

Seaman
Joined
Dec 12, 2006
Messages
74
Re: Buying a motor for parts?? Good idea??

Thanks for all the feedback folks and especially the detail from Frank. It is a 4 cylinder--thanks for the clarification. It's amazing how Chrysler took one basic design and spread it across so many horsepowers/years--talk about economies of scale! Take care and wish me luck on getting the 75 or potentially 105 to run. I'm sticking it on an old Glasspar 1969. Rebuilding the lounge seats this week....take my advice, buy them at $150-175ea. and save yourself the hassle. I'll have at least $100 in materials in each plus the labor (and I ain't cheap!). Live and learn!
 

bman1bpm

Chief Petty Officer
Joined
Jul 19, 2004
Messages
450
Re: Buying a motor for parts?? Good idea??

all motor manufactures like to save money haha.
JohnyRude 2cyl motors just have bigger bores for higher hp
Mercruiser 4.3 and 5.7 (chevy blocks) all all the same pistons, rods, etc, just one has 6 cyls and the other has 8.
theres many many more examples but I'll save everyones time.
 
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