Logo
FULL SITE MENU

2005 Nissan 8 hp 4 stroke compression

B

Boxie

New member
Would anyone happen to know what decent compression numbers would be on a Nissan 2005 8 hp 4 stroke. My model number is NSF8A2. Any help would be appreciated. Thank you...Jeff
 
If you look at your Factory service manual, page 3-18, you will find the procedure and the specs. 128 psi.
 
Thank you Paul,

I bought the motor used so I thought I found the manual on line. Apparently, there must be another one available. I combed that one looking for that data. Well looks like I have a problem 62 psi top 60 psi. bottom. I do have oil leaking down the leg of the outboard and oil inside the cowling. Maybe a head gasket? Darn, I guess I have been taken to the cleaners on this purchase. Any thoughts? Let me know...Thanks, Jeff
 
The Factory service manual is copyrighted, so is not available online. The aftermarket manuals are too general to be of much use. What is the oil level on the dipstick? Does the motor run? Did you try a leakdown test? The metal head gasket on these seldom fails, but there could be other issues.
 
Paul, ( model NSF 8A2 8hp)

The motor runs very well, no stalling or sputtering ect. which I find very surprising. It’s a kicker on a jet boat that weights about 1350#’s + people and gear. You responded to my earlier post about getting a high trust prop because the weight and the current prop. 8.5 x 7.5 my not be optimum for its use in a river. On a lake it will move the boat 6-7 mph but the RPMs would not come up. I don’t have a tach on it but definitely was not running at 5500 rpm. In the tank it would rev normal and idle all day. That’s why I checked the compression.

I have not attempted a leak down test yet nor have I verified the oil level. I will have to check the oil levels before And after use correct? Which I will do very soon. I was considering running ring free through the motor at a higher dose to clean it up and just maybe free the rings up if that is a possible issue. I have it already for my Yamaha jet so just a thought. Any thoughts regarding ring free for this application? Thanks again for your input...Jeff
 
My bet would be you have high oil. Probably oozing everywhere. Get that fixed. Remember no oil filter on those, so change every 50 hours or annually, whichever comes first. Then consider that to get proper compression readings you need to be over 500 rpm. It's probably just fine; You likely did not spin fast enough. Yes, running a decarbonizer won't hurt. Actually can help a lot, especially on old 2-strokers... but doesn't hurt on modern 4-strokes. I use the spray (OMC) that you spray through the throat. I would install the carb for a 9.8A3 (need to specify whether electric choke or not -- the chokes work opposite). Then get a decent tach. Get an HT prop (depends on the RPM you are getting now... whether you get the 5 pitch (heavy) or 7 pitch (moderate) weight. In your case, likely a 7 pitch... And be done with it.
 
Back
Top