Rebuilt Outboard Engine Reliability

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
dccarpenter
Posts: 2
Joined: Fri Jul 10, 2020 11:33 pm

Rebuilt Outboard Engine Reliability

Postby dccarpenter » Fri Jul 10, 2020 11:45 pm

What is the reliability of an outboard engine that has been rebuilt?

I have a 1973 Johnson 20-HP two-stroke-power-cycle outboard engine that I can get to start for a minute, but the engine hasn't seen water in years. I'm weighing having it completely done over or buying a new Mercury 20-HP FOURSTROKE engine for $2,700.

I am hoping for an engine I don't have to think about starting as long as I perform basic maintenance. I'm going tiller control with either.

I would think a good going over by an outboard mechanic and replacement of wear parts would come in substantially less than $2700 on the old Johnson assuming the powerhead is okay. The engine does not appear to have been abused or used hard. It was given to me by someone I trust who received it from a friend they labelled meticulous.

I would take on the rebuild task myself, but between work and my 4 year old my free time is scarce.

After years of looking and dreaming I finally picked up a Boston Whaler boat. I'm the proud owner of a 1965 13-footer. This boat won't see any weight other than me and a small cooler, and I'll be using a tiller extension to get my weight forward a bit (and I'm less than 200 lbs).

Don SSDD
Posts: 313
Joined: Fri Oct 23, 2015 6:58 am
Location: Nova Scotia

Re: Reliability of Outboard Rebuilds

Postby Don SSDD » Sat Jul 11, 2020 6:39 am

A rebuilt outboard engine only as good as the mechanic doing the rebuild. If a really good mechanic could be found, he could rebuild a really good outboard.

A mechanic who knows his trade can assess if your outboard is worth rebuilding and give an estimate of the cost before doing the job.

These old Johnson and Evinrude outboard engines were mostly sold in high volumes and changes year to year were minimal. The same parts were used on many different HP units over many years. Parts are generally available at low cost.

Having a vintage Boston Whaler boat with a period-correct outboard is a plus.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
Posts: 11673
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Rebuilt Outboard Engine Reliability

Postby jimh » Sat Jul 11, 2020 9:12 am

If an outboard engine has a powerhead that is “okay”, then it does not need to be rebuilt.

The term “rebuilt” as used in regard to older two-stroke-power-cycle outboard engines means the powerhead has suffered a catastrophic failure and needs extensive rebuilding with many new parts such as pistons, rings, connecting rods, cylinder re-boring, and so on.

No one would ever hire a mechanic to rebuild a 20-HP 47-year-old outboard engine because the cost would be much too high. Many hours of labor would be involved, many new parts, and probably some re-machining of the cylinder bores would be needed. The total cost could easily be thousands of dollars.

When finished, a rebuilt outboard engine can be reliable. The skill of the rebuilder and the quality of the components used will really determine the outcome. The quality of the original design and manufacturing will also influence the rebuilt engine reliability.

Usually only outboard engines of much higher horsepower than a 20-HP engine are rebuilt because their replacement cost could be $15,000 or more.

And usually 20-HP outboards don’t suffer catastrophic power head failures unless abused by their owners.

Your engine may need a new water pump impeller kit,new spark plugs, and perhaps a carburetor cleaning. That is not a re-build; that is normal maintenance.

dccarpenter
Posts: 2
Joined: Fri Jul 10, 2020 11:33 pm

Re: Rebuilt Outboard Engine Reliability

Postby dccarpenter » Sun Jul 12, 2020 11:31 am

Thanks for your replies.

I am glad to hear that outboard [engine powerheads] are relatively robust.

The 20-HP Johnson lived a freshwater-only life. I will do a compression check. If that comes back well [then I will do] basic maintenance on it. And then hope it proves a reliable runner.

I also have an [1974—always use four digits for year] Johnson 40-HP that saw saltwater use down here in Southern Maryland. I plan to do a compression check.

Thanks from out an outboard novice.

jimh
Posts: 11673
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Rebuilt Outboard Engine Reliability

Postby jimh » Mon Jul 13, 2020 10:13 am

The era of rebuilding high-horsepower outboard engine is probably over. The practice was common when outboard engines were almost all two-stroke-power-cycle engines with no valves and no forced lubrication oil sumps. A bad cylinder could be re-bored and fitted with a slightly larger piston at much less expense than buying a new engine. The engine compression ratio was low, the tolerances were sloppy, the engine designs were simple and basic.

At this moment, with the end of Evinrude production of two-stroke-power-cycle outboard engines, the new engine market in the USA is totally dominated by complex four-stroke-power-cycle engines with overhead cam systems with elaborate variable timing systems and forced oil lubrication systems. Performing a total rebuild of one of these engines is now far beyond the skill, time, and resources of a typical dealer’s service shop personnel. A highly skilled technician who builds high-power four-stroke-power-cycle engines by hand for a living now works for a NASCAR race team, not your local outboard service shop.

If you do happen to blow up a 400-HP VERADO race engine, it will go back to Mercury Racing Engine division for a factory rebuild; a local mechanic with a toolbox and some wrenches is not going to work on a $35,000 engine.

biggiefl
Posts: 897
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Compression Check Procedure

Postby biggiefl » Mon Jul 13, 2020 12:05 pm

Compression tests on a pull start motor can be tricky. Personally, if the engine is a bit hard to pull, it is OK as you only have two cylinders.

If you do a compression check, just look to see if the cylinder pressure measurements are close to each other. If the compression is supposed to be 120-PSI, you probably will not get that high by pull starting it. Also, all testers are different and give different values.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

jimh
Posts: 11673
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Rebuilt Outboard Engine Reliability

Postby jimh » Mon Jul 13, 2020 12:32 pm

We seem to now be far afield of the original topic.

The thread is asking about the reliability of rebuilt outboard engines.

For advice on how to assess an outboard engine see the REFERENCE SECTION article on that topic:

Assessing Used Outboard Engines
http://continuouswave.com/whaler/refere ... Check.html

To discuss availability of engine diagnostic software for modern engines, please start a new thread.

To discuss effects of saltwater on engine maintenance and service life, please start a new thread.