1974 25 HP Johnson

[JohnAB]

Good day,<br /><br />I have what I believe to be a 1974 25 hp Johnson. Model # 25E74M Serial Number C47280. Was wondering if it is possible to hook a tach up to this engine. It is a manual start.<br /><br />Interestingly enough, when I went to a dealership here, they stated the model # didn't exist. I was in getting a new orifice plug for it.<br /><br />I do have a Clymer shop manual for the engine but am having a hard time determining if I can hook a tach up to it.<br /><br />Thanks for your help.

 

[rolmops]

Re: 1974 25 HP Johnson

Hello.<br />The serial# does exist and it is a 1974 electric start 25 horse.<br />You can very easily attach a "tiny tach" tachometer to it by wrapping the red wire a few times around the lower plug wire and the white one to a ground.<br />Go to search on the top of the page and type in "tiny tach" it will get you the info of their website.If that does not work just google it.<br />Good luck.

 

[JohnAB]

Re: 1974 25 HP Johnson

I figured it was a valid number and that at one time it was an electric start. Starter motor plate is still there but the starter and such is gone.<br /><br />Cannot find a rectifier or any such thing on it though.<br /><br />Will peruse the Tiny tach site.<br /><br />Thanks.

 

[rolmops]

Re: 1974 25 HP Johnson

I don't think they ever had rectifiers,they were the electromagnetic type ignition.

 

[JohnAB]

Re: 1974 25 HP Johnson

Thanks for the info. Went to the Tiny Tach site and see they have a Canadian Distributor. Will be ordering a tach.<br /><br />Now that I have that covered, I am hoping I will be able to hook up a battery so I can run and charge a trolling motor.

 

[Chinewalker]

Re: 1974 25 HP Johnson

Hi John,<br /> Your motor never had a charging system and there was never any provision to add one. You may want to consider a solar trickle charger type system to keep the battery topped off. .<br />- Scott

 

[Paul Moir]

Re: 1974 25 HP Johnson

I almost never disagree with Chinewalker, but I though 1974 was the first year they offered charging on the 25hp. Although don't see anything that looks like a rectifier on this '74, but it's got the new-style ignition.<br />I could be wrong though.

 

[Chinewalker]

Re: 1974 25 HP Johnson

Hi Paul,<br /> The 1974 models had the low tension magneto with the driver coil and "maker" points. Now that I think about it, I suppose it would be possible to install a stator coil for an alternator under the flywheel in one of the spots where a magneto coil would have been in an earlier generation. The armature plates on the low-tension mags are laid out quite similarly to those used on the older magneto plates. The driver coil occupies one of the earlier coil spots, while the other is empty - perhaps for an alternator coil? Hmmmmm.... I've never seen one with an alternator set-up and as such I suspect they're as rare as the proverbial hen's teeth...<br />- Scott

 

[Paul Moir]

Re: 1974 25 HP Johnson

That sounds likely. I found this at the Old OMC Site indicating a 45W (3.75A) generator on C.A. models (Corrente Alternata, Alternating Current, 'Charging' models I presume). <br />Elsewhere in the brochure it seems to mention this as a fitted accessory rather than something that came equipped on a standard model. That is if I'm reading my babelfish translation properly.<br />Thanks for filling me in Scott!