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BF150 compression value

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fastkurve

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"Hi,

Would like to know wha

"Hi,

Would like to know what value I should expect for a compression check, also, does it make a difference if checked with power lever at full throttle or idle position ?
thanks,

Robert"
 
The compression should be 222

The compression should be 222 - 250 psi at 200rpm

If should be measured at full throttle. Be sure to use throttle only (not in gear) and disconnect the safety landyard to eliminate any spark.
 
"Thanks a lot for the info. I

"Thanks a lot for the info. I had checked it, and found 120 PSI at 3 cylenders and 95 at the fourth one, full throttle, not in gear. Does not look too good....What I found strange, the spark plugs look pretty good, light brownish and engine running smooth. The only concerns I had was that I lost 6-7 mph on the top end and it was not pulling as hard from the hole as t was when I bought it in 205 (was a demo engine with 40 hrs done). Otherwises, fuel consumption did not really change, strange.....?????"
 
"You may want to see if you ca

"You may want to see if you can borrow a different gauge and take the readings again.

Also, make sure full throttle is really full throttle...is the throttle arm on the engine against the stop? A stretched or out of adjustment throttle cable, could give you a false reading as well as lower top end.

If there is still a difference, spray some oil in the low cylinder and see if it brings up the compression.

You may also want to take compression after the engine has been warmed up to see what you get.

A leak down test should be done next.

It could also be the valve clearances need to be adjusted."
 
"Thanks for suggesting, I do h

"Thanks for suggesting, I do have a second gauge, so I would check it with it, but the first gauge was used recently to check a car engine compression, it happens to be an Honda accord engine by the way lol, and was reading a solid 175 PSI at all four holes...As for the throttle being at WOT, I looked at the linkage and seemed to be positioned at the full max stop. Did not think about sqeezing some oil i it and double check it afterwards, another step to be done.As for the leak down check, it would be at the dealer to be done, I do not have the equipment to do so. As for the valve clearance, would it be that sensitive , I mean, how bad clearance need to be to affect compression value that much ? should had I notice bad engine idliing, or hesitation from the engine if it happens to be this ?? thanks for your feedback, by the way !"
 
"Update -Update- Update

Che

"Update -Update- Update

Checked it with a second gauge and ended up with similar results. One thing though, I asked my son to keep cranking the starter 8-9-10 times in a row and compression ended up rising up to 155-160 PSI ??? Could it be the fact that fuel was accumulating in the cylinder and helped sealing the piston-ring-cylnder all together ? That's was I supposed then..."
 
"Not sure if the fuel is givin

"Not sure if the fuel is giving you the increased reading.

Be sure to crank the same amount of time on each cylinder.

Also, be sure that the battery is fully charged so the engine cranks as close to the 200 rpm as it can. It probably will not crank that fast so your compression readings may come in lower than the specs."
 
"-Just in Time -

Yes, I&#39

"-Just in Time -

Yes, I'm sure that I had positioned the lever to WOT.
Even check the linkage if it was working ok, and yes it was.

-Mike-

I even hooked up my battery charger on the battery and set the switch to have the "
 
"Question:

Is there any spe

"Question:

Is there any specification/recommendation to check the engine compression while engine is still "warm" ? Personally, I never did that with a warm engine, but just curious to find out if Honda is recommending such sort of recommendation...

thanks,"
 
"Well, the dealer did check i

"Well, the dealer did check it and agreed that something wrong is going on, he kept the boat and will talk to the Honda tech on Monday.

I will let you guys know about further development.

thanks for your support,

Robert"
 
"Here's an update:

Took

"Here's an update:

Took the boat at the dealer,did the same as me and concur compression check values. Also did a leak down check and ,based on their statement, shown a bit of leakeage through valves.

Now my question, they said that the low compression was mainly due to the fact that piston rings groove were all aligned instead on being offset by 180º
from each other ?? I personnaly do not believe that such condition would explain such a loss from the compression check we did...what would be your thoughts about this ?

To me, offsetting the piston ring groove, is just a common sense thing, having such impact really surprise."
 
"I have no idea how they could

"I have no idea how they could come to that conclusion from a leak down test. Fishy, fishy, fishy.

How old is the engine and how many hours? How has the engine been used? What kind of fuel have you been using?

I would consider decarbonizing the engine. YamaLub Rig Free or SeaFoam will do the job. Follow the directions closely."
 
"Other than their theory, did

"Other than their theory, did the leakdown indicate things were ok?

How much is a little leakage at the valves? Did they recommend adjusting valve clearances?

Were all cylinders the same?

I agree with W D. It seems very unusual for all cylinders to have the rings oriented the same unless it was done at the factory. You said you have recently lost 6 -7 mph...so it must have been something that has happened recently.

What did they say should be done?"
 
Your engine wont have 250psi c

Your engine wont have 250psi compression!!!

Normal compression would be around 150 to 160psi.
If yo had 10psi difference i wouldnt worry about it at this stage.

Run the engine (to get it warm) and disconect the fuel line and wait for it to run out of fuel.

Do your compression test with WOT and count about 5sec's per compression test. Then squirt a couple of squirts of oil into the cylinder and check compression again (do this for each cylinder) the oil will only effect the compression if you have a ring problem!!

To check the valves if the are sealing a cylinder leak down test is required...if there is a valve problem you will hear air escape through the problem valve and out the exhaust or through carby intake.
 
"I will try to respond to ever

"I will try to respond to everybody query or comments:
1-the engine is a 2004
2-it has approx 350 hrs
3-I'm using regular fuel
4-engine used mainly to reach fishing spots & been cruise 95 % of the time at 4000-4200 rpm. otherwises, cruising for a ride or skiing once in a while
5-the leak down test is required to figure out the potential valve to seat leakage, the low compression value was determined using a standard gauge while cranking the engine starter
6-the engine is now dis-assembled
7-as per their own statements: "leak down tests shown some leakage"
8-nothing special happenned with the lost of top speed, it is just a matter of feelings from me that the engine did seem as responsive, gradually loosing power from my 5 year of ownership, then I did 3-4 trials at wot ad observed the lost of top speed then, that's all
9-they are talking to honda they said, and waiting for their feedback about the piston ring gap all aligned and if they agree with this as the basic reason
10-the manual states 225 psi min.
11-the manual does not state to warm up engine prior compression check
12-I did my own compression check and obtained 120 psi at 3 cylinders and 95 psi at the fourth one & the manual states that the max compression should be obtained with 9-10 strokes (which I personal foind too muh, I would expect to reach it with 4-5 strokes max, but it is just me and my own exerience with piston engine)

I would like to thank everyone for queriing and sharing, it is fun and pleasant to have your feedbacks, thanks again"
 
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