circa 1980 Johnson 100HP 4cyl - info needed

djm3801

Seaman
Joined
Apr 12, 2014
Messages
64
Looking at a boat with this motor. I have done about everything to a car engine that can be done so engines do not scare me. On this one - what is general opinion of this model? Are parts still available? It has not been run in a long time - never a good thing - but how reliable were these in general? Opinions welcome and thank you.
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,135
you might need to track down the year as there were a few improvements around 1978
most of these were reliable so long as you took care with the maintenance- water pump/thermostats and that you didnt run it lean with a blocked carb.
You should try and find out if it had being oiled up before storage, id be concerned about rust/pitting on the bearings
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
The crossflow V4 was the most successful outboard that OMC ever made. These were made by the thousands in a number of different configurations. They were reliable, torquey engines that were endeared to many consumers for many years. Since they were so popular, and so many were produced, parts are readily available, either new or used. They did smoke a lot and were not very fuel efficient when compared to today's engines, but that was not a detraction back in their day. If you read through these forums, you will find many folks still repairing these engines that are from the mid-to late 70's. This model has a number of solid, modern improvements, such as fuel primer choke, all electronic ignition, charging alternator, modern power trim system, thru-hub exhaust which uses props still made today, mid section water silencing. They are relatively light, when compared to today's 4 stroke engines of similar hp. Of course, any engine is only as good as the periodic maintenance that it was given over the years. So, do your due diligence and check the gear oil for water intrusion, hear it run, check the compression and make sure you get all the parts: control box (shifter) and the power trim electrical control box. Adjust your $ offer accordingly.
 
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