TOPIC: merc vers johnson

Iam running a 64 Johnson 40hp and it moves my 1960 span America v.i.p. at 22-23 mph. can I up the speed by running a 1960 merc 300? ive always been told that mercs put out more hp then there rated is this true? I like the looks of the merc but I like the ez to work on of the Johnson. Bob

I'm not sure what if any gain you might have if you swapped to a Merc 300, 4 cylinder,...BUT
The cool thing is if you didn't gain enough more, a lot of other Merc 4 cyl powerheads with more HP are just (1) gasket away in a powerhead swap.
You would be able to jump to 40 HP, 45 HP, or even one early series of 50 HP 4 cyl Merc powerheads. How cool is that!!!

Granted,...There are a few unique tools required for 'deep repairs' on the classic Mercs, but lots of old farts like me have those tools and really enjoy helping guys 'shift over to the Dark Side'.
Yes,...I am a Mercaholic.

doc F

Doc thanks for the reply. ive worked my but off giting this Johnson up and running perfict. and its a nice motor. I put a 58 super quiet hood on it and it looks nice and vintage. BUT iam kinda hooked on the looks of them ghost white merc.s . this 300 has some lower unit problems and the top end is unknown. I have some 70 -71 50 hp mercs. will a top end this new work on this old 300? thanks Bob

The lower unit on the '55-early '61 Merc 4 cylinder motors has it issues. Often the steel drive shaft is pitted at the place the seal under the water pump housing makes contact. The cure is total disassembly, clean off the rust, and install a speedi-sleeve.
You would want to take a close look at where the seal runs on the prop shaft while it is disassembled. Fish line is that seal's worst enemy, and can score the prop shaft where the seal runs.
You can't put a speedi-sleeve on the prop shaft, because then the needle bearing in the bearing carrier would not be able to slide over the speedi-sleeve during reassembly. The cure for the prop shaft is to either have the prop shaft surface repaired by an expert, or machine the recess of the seal a bit deeper into the bearing carrier - consequently making the seal runs on a different area of the prop shaft that typically is okay.
This 'project' calls for several specific Mercury tools, and if the lower unit has been used in salt water or corrosive fresh water, it is a tough "5 hammer job"!
A sweet fresh water lower unit should disassemble fairly easy when armed with the right tools, or home-made ones that will do the job.

From the second serial group in 1961 up through all the remaining model 500 Mercs,...The lower unit, driveshaft housing, and the powerheads,...Will not interchange with the earlier parts - like your 300, etc. Lots of changes, but the later model Lightening Energizer ignition can be retro-fitted to the earlier 4 cyl Mercs & can really make starting and idling performance much better if the original magneto on your 300, etc is giving you fits.

One very cool thing I've seen done before is to simply paint the later 500 4 cyl Cloud White, and apply earlier vintage decals.
The PPG color code for Cloud White is 3398, or 1992 VW Cashmere White.
The later '70s and '80s 500 has a much better designed lower unit, and some major improvements on several different ignition systems.
Rarely will a specific Mercury tool be needs on these and parts are much easier to find from Mercury dealerships, Sierra Marine (NAPA), and trusty old EBAY.
doc

thanks doc. ill let you know how it turns out. Bob

Bob,

The idea of Mercury engines putting out more than what they were rated for is an old wives' tale. During WWII Mercury made engines that had to comply with the requirements of the military - and that demanded a far more conservative rating for power. As I understand it, for a few years after WWII kiekhaefer continued the practice of under rated the HP claims on the motors they built. However, that practice ended in about 1955. By the mid 1950s ALL standard production motors were rated at actual power output. In fact, it wasn't until the introduction of the Merc 800, that the engines wore a model number that actually corresponded to the actual power output. Many people think that the Mark 55, 58, 75, 78, model numbers denote horsepower - but they don't. The Mk 55 made 40hp, the Mk 58 made 45hp, the Mk 75 made 60hp, and the Mk78 made 70hp. So this BS made for a LOT of confusion in the marketplace.

I don't know how heavy your boat is or how long it is - but going DOWN in HP certainly will not make the boat faster, no matter the brand of the motor. The Big Twin OMC motors had more bottom-end torque than the little Mercury motors. The Merc had a more efficient lower unit, and it could wind up higher than the OMC could. They were fantastic little motors - but don't expect them to put out more power than what they are rated for.

Your OMC may have room for more tuning and a better prop selection - chosen specifically for the application.

As this is a forum to state ones opinion, being one who grew-up in a Mercury outboard dealership from basically birth, I long have tired of hearing that "Mercurys are fast, but won't pull". Seeing as Mercury was 21 years old (remember also that there were no 1943-45 models, and nil 1942 models) in 1960, Johnson was 38 years old, and Evinrude 51 years old, yes, most Mercury dealers were far newer and too often far less experienced dealers, so a great many Mercurys were delivered to the customer with the propeller shipped inside the carton, instead of being exchanged for the propeller pitch correctly suited for the boat (and the customer's usage) it was installed on (frankly, the practice of delivering boats with the outboard incorrectly pitched, or even mounted correctly, still happens in cases to this day). Fortunately, both Ted Ferguson and my father started as racers, and they knew to prop correctly. I can still remember hearing my father say to customers that "If I cannot get a Mercury to out-pull the Evinrude or Johnson you are considering that I will give the outboard to you". We never ever had to eat his words and give an outboard for free.
As to the 1964 Merc 300 versus your 1964 Johnson 40, many people do strongly feel that the 1960 Merc 300 is essentially a 40 horsepower, and as they are basically a prior Mark 55, so if the Merc 300 is a healthy example, you certainly will not be slower, and I do think that the far improved lower unit shape will likely net a small improvement. The Merc 300 is a very well thought of vintage Mercury, with especially nice idling and running qualities, with very good fuel economy. This is hopefully a link to another site discussing the Merc 300, and includes a You Tube video of one running: johnsoldmercurysite.com/phpBB3/viewtopic.php?f=7&t=12288&sid=6d370b7bf3e181e

Regards,
Joe
www.fergusonpoolemarine.com
This email address is being protected from spambots. You need JavaScript enabled to view it.

thanks guys for the info. my boat is 580 lb and 14 ft. it must be a rumor that all outboards are hp tested at the flywheel and merc is tested at the prop shaft. after talk to the good dr jumped on the 300 that was on craigs list but I missed it by 2hr. rats so it looks like ill be sticking with the ol 40hp Johnson. thanks for the help Bob