Compression test
- Thread starter Joker2
- Start date
tsubaki
God
Can't say it's correct but I usually remove all the plugs, hold the throttle butterflies wide open and pump each cylinder till the gauge levels out.
This is done using a remote start switch (jumping the solenoid) with the key off.
Hoping for no more than 10% difference between the cylinders.
Never been able to determine what the "correct compression" for each engine was. With the 150's, I expect 90psi and above is pretty good on the crossflows, I would think the loopers would be higher.
This is done using a remote start switch (jumping the solenoid) with the key off.
Hoping for no more than 10% difference between the cylinders.
Never been able to determine what the "correct compression" for each engine was. With the 150's, I expect 90psi and above is pretty good on the crossflows, I would think the loopers would be higher.
Joker2
Junior Member
Sounds good, butterflys open is the same as manually holding the throttle full open at the engine corrrect? Jumping the selenoid is the same as cranking the engine with the safety lanyard (kill switch ) disconnected right? Just curious because other things i have heard say that but I trust you guys on this site.
tsubaki
God
I didn't think about the kill switch doing the same thing but yes.
The wide open throttle lets all available air into the cylinders.
Some people will say do it after warmed up or with oil to improve the accuracy or cold is the best test.
It's gonna depend on a lot of factors. For me, if it don't perform a good test cold, the engine's questionable period.
The wide open throttle lets all available air into the cylinders.
Some people will say do it after warmed up or with oil to improve the accuracy or cold is the best test.
It's gonna depend on a lot of factors. For me, if it don't perform a good test cold, the engine's questionable period.
Destroyer
God
Seafoam is an aftermarket product that keeps your carbs and injectors clean of residue, shelac, etc. It's got a good, well deserved, reputation within the boating and automotive industry. Simply put, it does what it's advertised to do. While I've never used it, I'm sure that the Evinrude Engine Tune does everything that it's advertised to do also.
willy
God
Just remember, Sea Foam is a very good product for doing the engine clean, carb clean, and for de-carbing your engine.
What it does not do is treat your fuel for ethanol gas. You MUST use a separate treatment such as Evinrude 2+4, Startron etc. or your fuel will start phase separating within a couple of weeks, quicker if there is extra moisture present.
Ask me how I know
What it does not do is treat your fuel for ethanol gas. You MUST use a separate treatment such as Evinrude 2+4, Startron etc. or your fuel will start phase separating within a couple of weeks, quicker if there is extra moisture present.
Ask me how I know
THEFERMANATOR
God
Seafoam is not even close to the same as EVINRUDE engine tuner. Seafoam can be mixed with your gas and run through that way for decarbing whereas EVINRUDE engine tuner CANNOT be mixed with gas and ran through your carbs. The engine tuner is meant to be injected through your priming system for a deeep decarboning, and I use it for soaking my carbs in as well. It WILL destroy fuel lines in rapid ordeer though, so be careful with the EVINRUDE engine tuner. EVINRUDE does make the 2+4 product that is like SEAFOAM.
Destroyer
God
I thought that I remembered you mentioning that you used the Evinrude tuner stuff for soaking your carbs, and I meant to ask you way back then if there was any problem with it attacking the plastic carbs that are on my engine.
Destroyer
God
Just remember, Sea Foam is a very good product for doing the engine clean, carb clean, and for de-carbing your engine.
What it does not do is treat your fuel for ethanol gas. You MUST use a separate treatment such as Evinrude 2+4, Startron etc. or your fuel will start phase separating within a couple of weeks, quicker if there is extra moisture present.
Ask me how I know
Another good product to treat your gas for separation is the new Sta-bil for Ethanol.
THEFERMANATOR
God
I thought that I remembered you mentioning that you used the Evinrude tuner stuff for soaking your carbs, and I meant to ask you way back then if there was any problem with it attacking the plastic carbs that are on my engine.
I bought it just for doing plastic carbs as regular caustic carb dip will detroy plastic carbs. It will eat rubber fuel lines though in short order. Doesn't seem to bother viton needle and seats, but the neoprene ones will swell up a bit in it.
Joker2
Junior Member
I have been adding the Sta-bil for ethanol every time I get gas since I got the motor ( last Sep. ) when it was newly rebuilt. I am thinking more about a product for decarboning. I just got a known good compression tester yesterday, I will do that first and see what my results are. I only have about 18 hours on motor, ( 10 hrs of break-in running double oil ) it seems like not enough to have to decarb. I have a 20 minute ride at idling speed each way till I get to open water every time I go out, wondering about how that is for buildup ? trying to get it to run smoother at idle and get more power out of it, only 45-4900 RPM's max 25 MPH on GPS
Joker2
Junior Member
Well went out today. Got to boat swap out the fuel / water seperator filter next off to gas dock ( 16 Gal high test ), had a problem threading on my Perko plastic gas cap, I deformed the threads and just forced it on, ( I know I need a metal one )off to go tubing, everything normal, tubing for about 1 hour, through all rpm ranges a little opened up, all fine, then it happened, she started cutting out on me no power, got it started with the fast idle lever a few times, drove a couple of hunded feet it happened again, started it dropped down the fast idle she wouldn't stay running, dumped my water seperator real quick and put it back, looked OK, also right before this happened as I was backing away from the beach slowly, into a slight chop, a little wave came over the transom, ( not sure if this has anything to do with it ) problem started shortly after that happened. Could water have gotten in somehow ?Not sure what to do, Tomorrow I am checking comp. Any chance this could be a fuel pump problem?
Joker2
Junior Member
Did comp. test this morning with a brand new screw in type tester. Had to do it with the engine cold, I can't start it. I got 120 lbs. on all three starboard side cyl. Had 100 lbs. on all three port side cyl. Also this is the 3rd time I found black buildup on the lower starboard side plug. I just changed the plugs last week, only ran motor about 2 hours since. I will try seperate fuel, I think those numbers were like that since I got boat, I feel yesterday was fuel related, just wanted to check comp. Is there a problem with these comp. numbers ?
Last edited: