Honda 115 compression check

jworks

Cadet
Joined
Mar 25, 2019
Messages
24
What should the compression be (or reasonable range) for a 2008 Honda 115 hp (EFI)? I rented a compression gauge to go look at a used boat and I'll do a compression test. Also, are the spark plug holes the same for a Honda as they are for any other engine? Someone told me they thought the holes are smaller, thus my gauge may not fit. I don't know, that's why I'm asking.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
There are 2 types of spark plugs and their holes, the standard wider diam used on most old and newer 2 strokes motors and a a less wider diam usually used in newer 4 strokes motors. Ask the seller which type of spark plugs does the Honda 115 HP uses, if it's the one with less diam check to see if the tool lessor has an adapter to screw it at the end of the gauge

Happy Boating
 

jworks

Cadet
Joined
Mar 25, 2019
Messages
24
Sea Rider, thank you for replying. The owner previously told me over the phone he "thought" an adapter of some sort was needed to fit compression gauge into the spark plug hole. I can tell talking to him he doesn't know a lot about boats (I'm somewhat better but no expert). A local Honda shop told me this is not true, a regular compression gauge fitting would work. Problem is, he's 2 1/2 hrs away and who wants to drive that far and perhaps not even have the right part to do the check. I don't know. I may just have to drive there and see for myself. Sea Rider, do you know anything about these Honda 115s? Not many of them are owned around me. This is mostly Merc and Yamaha area where I live. I've read some good reviews online and some that weren't good at all. Have you had any experience with them?
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
Messages
12,345
Sorry Jworks, don't work with Honda outboards, I'm a Tohatsu junkie. Personally wouldn't want to own any Honda outboards due to being complex, parts availability, service, manuals, cost etc.

If you provide year of manufacture can look for those spark plugs to determine the size and diam. Wouldn't want to travel that far to find out that the standard plug of the compression tester is way larger in diam than the motor plug hole as to carry an adapter..

Happy Boating
 

jennyo

Seaman Apprentice
Joined
May 6, 2009
Messages
46
Small plug is a 14 mm thread 5/8 socket.Large plug is 18 mm thread 13/16 socket.
Compression should be at least 100# minimum.
 
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