What did I buy?

[Toyman991]

Today I purchased a running 1956 AD-10 M with decals on the cowl that say 5 1/2 hp. Now I find that an AD-10 is a 1956 7 1/2 hp motor. The serial number on the model plate differs from the number on the freeze plug on the powerhead. Should these match? <br /><br />Plate Serial #1437185<br />Freeze Plug #1560456<br /><br />How can I determine whether this motor has the correct powerhead with either the wrong hood or decals? The plugs are J4C and not J6C which would indicate that at least the plugs are correct for the 5 1/2. <br /><br />Aside from from these serial number discrepancies, are there any other distinguishing characterisics between the two motors?<br /><br />Please help me solve this mystery.<br /><br />John

 

[rolmops]

Re: What did I buy?

Hello.<br />The plate serial is '56 and the freezeplug serial is '57.<br />This is really not as strange as it seems.It is possible that the transom clamp has been exchanged,people often cannibalise old engines in order to keep within their budget.My gut feeling is for you to go with the freeze plug.The 5.5 horse is 8.84 cubic inch and the 7.5 is 12.4 cubic inch. good luck.

 

[Toyman991]

Re: What did I buy?

Thanks for the info Rolmops. Is the difference in displacement due to bore or stroke. In other words, could I use a set of calipers to measure the bore and settle it once and for all?<br /><br />If, by chance, the freeze plug is an OEM parts counter replacement, would it have a serial number on it?<br /><br />Thanks for any help in solving this mystery. It looks like I may have a mongrel on my hands.

 

[Chinewalker]

Re: What did I buy?

Hi Toyman,<br /> There's really no confusion between the two blocks if you know what you're looking for. The 5.5hp block has no transfer port covers - they're cast right into the block. The 7.5 would have two cast aluminum covers held on by four screws each on the starboard side of the motor (one for each cylinder), near the cylinder head. The 5.5 does not have these.<br /> Also, a 5.5hp hood would not fit the 7.5hp powerhead - mounting bushings and such are in different places and the 7.5hp hood is larger than the 5.5hp hood...<br />- Scott

 

[Toyman991]

Re: What did I buy?

Chinewalker,<br /><br />You've solved my mystery! My block has no transfer port covers so it is a 5 1/2 horse (CD model, I presume). Apparently, everything below the pan is from an AD-10. Does this present problems when I begin to work on it? My Clymer book covers both these models, are there differences (aside from the model plate) between these two legs, etc.?<br /><br />Also, what are your thoughts on these little motors? Any areas prone to problems? I do have to pull the powerhead to unhook the shift rod for waterpump service, right? Any tips in this regard?<br /><br />Lots of questions, I know, but I truly appreciate you gurus can offer.<br /><br />John<br /><br />P.S.: Love your website, Chinewalker!