john 25hp 1972 paint/carb

[henning_dt85]

Hi, got a 25hp johnson as a parts engine for my 1970 20hp. Outside it has the standard green, but inside the paint is dark green (standard 1969-1971) on the halve side with carb/reed, and the side with cylinder it has same color as the outside. Is that standard? ( look at this ad, it has the drak green other places: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2487025306&category=50439 )<br />Is the paint for 1970 called dark green or forest green?<br /><br />Then, the carb. If that is ok, could the carb be installed at the 20hp ( conversion from 20 to 25 hp)? if not, how to get the 1000 rpm the 20hp dont have?

 

[rickdb1boat]

Re: john 25hp 1972 paint/carb

RPM's have nothing to do with the size of the motor. Running at peak efficency and the proper pitched prop will take care of that. I have no idea on the colors...

 

[G DANE]

Re: john 25hp 1972 paint/carb

Oh Yes rickdd1boat. <br /><br />On the 73 20HP tiller the label says 20BHP at 4500 Rpm. On same vintage 25HP it says 25BHP at 5500 Rpm. The difference however comes from higher piston tops, which is the reason there is riveted weights on the cranckshaft of those 25HP's. Apart from that the motors are identidal. To answer your question here from Denmark Henning, you will have to change pistons. This jump in Horsepower is genial. Same block, head, exhaust,propeller ect, just the pistons and weights riveted on cranckshaft. Maybe if you could shave the head a bit you could get the higher compression it takes that way. I was told the weights on cranck reduces the "dead" room in cranckcase too, increasing vacuum.<br /><br />Motors from that vintage was painted with same paint everywhere. Different colours means a part got overheated, or part swapped from another motor. These are old ladies, that probably got some beauty surgery now and then

 

[G DANE]

Re: john 25hp 1972 paint/carb

In 72 they got the lighter metallic colour, but most parts still matched.

 

[G DANE]

Re: john 25hp 1972 paint/carb

Oh - I fotgot, both have the same carb, I dont know with jets. The HP is marked on the reedplate, on a visible "EAR" I never could see any difference on either plates, guides or reeds though. Measured everything to find some seacret.

 

[henning_dt85]

Re: john 25hp 1972 paint/carb

The carb from the 25hp has partno. 313355. the 25 has 5500 rpm and 20 4500 rpm, thats correct. Could a 18hp 1963 head be used on a 20hp 1970? How much to reduce ( in MM)?

 

[G DANE]

Re: john 25hp 1972 paint/carb

I dont know, sorry