Compression and transfer port covers, Force 150

[pastorbud]

So I'm trying to figure out if my 150 hp powerhead is useable. Compression test showed about 160 on the bottom four cylinders and 125 on the top. In another post an experienced guy suggested I take a look at the transfer ports. When I pulled the transfer port covers off, I found that many of the bolts were loose (undid with my fingers!) or even missing.

So, my question is, are those compression numbers even reliable if the transfer ports covers were loose?

I ordered new gaskets, and will re-test.

BTW, I looked for damage and blockage while they were off. Saw none. Here are pics inside the #1 and #2 transfer ports.

 

[pastorbud]

After I re-test, if it's still out of tolerance, I'll pull plugs, and if necessary, the head.

 

[pnwboat]

Loose transfer port covers shouldn't have any affect on compression readings. It may affect air/fuel delivery to the cylinders if they are loose enough to leak.

 

[tommarvin]

Nice pictures, If your compression numbers are what you say they are, I have read that one piston that's more than 10% compression off you have to fix that piston.
Did the motor run fine before this?
There is a process to do a compression test correctly, wide open throttle, all plugs out, did you squirt anything into the sparkplug hole before the test, did you ground the spark plug wires so you don't damage the ignition system, I don't know how to do a compression test correctly to many factors,that's why I do a leak down test, it's so much easier, you never start the motor, safer,can't break anything, no water needed, faster, HF has a kit for 40 bucks.
Do you have a factory service manual for how to torque down a head, then don't forget to re torque after I think it's 20 hour's of motor use.

 

[pastorbud]

I bought it --just a powerhead no leg or lower unit--for the coils and CDI boxes. But now I'm trying to see if it's worth using on a bowrider I bought last fall.

The ignition is removed right now, but it had spark on all 5 before I took that off.

Since I haven't mounted it to a leg yet I haven't run it.

Kinda want to figure out the compression problem before I spend money for the midsection I need to mount and run it.

 

[pastorbud]

Is there a sticky somewhere for compression test procedure? Or leak down test? ( I don't even know what that is! )

 

[jerryjerry05]

​The damage would probably be on the skirt on the top piston??
Is the exhaust chest easily removable?
If the ports were loose then maybe the exhaust was off before??
If so do an inspection on the exhaust side and look at the skirts.
The screws on the exhaust side can be tricky if they have never been removed.
Don't need to do a leak down test.

A comp test. Your ignition is off so no need to worry about blowing the packs.
You don't need to open the throttle all the way.
Remove the plugs.
HOTTT battery.
Hook up tester.
Turn it over until the gauge stops going up.
Your test results might be right??
The engineers were messing with compression ratios on the later 150'S
A FACTORY manual for your specific motor will tell you what you need t know.
The crap manuals give some info but cover way to many models to be real specific.

You look under the pack for the foundry stamp?
The A means nothing for years.
I have a couple factory manuals for the 150 just tell me the year and I'll post the readings.

Some people are a fountain of mis-information!! Be careful with what you read and try to implement.

 

[pastorbud]

So, just to be sure I got this.... I do the compression test with all the plugs out? And should I spray any lubricants in there first?

 

[flyingscott]

No spray no lubricants in it they give you a false reading. If the cylinder is really dry spray fogging oil in it and spin the engine a couple of times to blow the excess out before you test the compression. Make sure the plugs are out for this and the throttles don't need to be open for a compression test.

.

Do not worry about the LEAK DOWN TEST they are only used after all other trouble shooting methods are used. And even then it is a last resort. People who tell you they are easier than a compression test 2 things have either never done one or don't know what they are talking about. If a leak down test needs to be done take it to somebody who knows how to do one.

Jerryjerryo5 is one of the the guy you want to listen to on this site very knowledgeable.

 

[jerryjerry05]

​Thanks Scott!!

​The oils or silicone spray will fill in any holes or leak spots giving false readings.

IF??? your cylinders are dry, a bit of WD-40 and rotate the crank.
Then let set 24 hrs before a comp test.

But the amount of turning over a comp test requires won't hurt anything.




Some people are a fountain of mis-information!! Be careful with what you read and try to implement.

 

[pastorbud]

Reran the test. Got 150-156 pounds on all 5 cylinders.

 

[pastorbud]

Now I gotta find a driveshaft cover.

 

[pastorbud]

I think this one would work... Not cheap. There was one available before for $125, but it sold fast.

 

[pastorbud]

Oops that's a 20". I need a 25".

 

[pastorbud]

There's the one I need.