150 Intruder Compression Check

J

jigs1950

Cadet
Joined
Oct 14, 2008
Messages
6
Compression reads are 60, 60, 60, 70, 70, 73. This was a hot test and I was wondering if a rebuild is needed?
Motor runs great, no problems.
 
Randybeall

Randybeall

Petty Officer 1st Class
Joined
May 2, 2008
Messages
319
Re: 150 Intruder Compression Check

Those numbers seem low, did you tie the throttle open while runing the compression test? If not, you are low but even, perhaps it is time for a set of rings to get back to full horsepower. Rember, when you do a compression test it is important to have a fully charged battery, and to open the throttle fully to prevent air flow restriction.
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
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Nov 11, 2005
Messages
51,019
Re: 150 Intruder Compression Check

how did you do the test? did you do it with all the plugs out, and turn the motor over 4 to 5 rotations, if so, try another gauge, very unusual for them to be that close and low. did you use the screw in guage?
 
J

jigs1950

Cadet
Joined
Oct 14, 2008
Messages
6
Re: 150 Intruder Compression Check

I'll try with the carbs wide open, they were closed. Yes, it was a screw in gauge. That gauge gives higher reads on differant motors.
 
J

jigs1950

Cadet
Joined
Oct 14, 2008
Messages
6
Re: 150 Intruder Compression Check

New reads with the carbs wide open.

70, 70, 70, 89, 86, 83

Fully charged battery too.
 
J

jigs1950

Cadet
Joined
Oct 14, 2008
Messages
6
Re: 150 Intruder Compression Check

1995, I was thinking the same thing. Decarb just might improve the compression, espically if the rings are carboned up.
 
iwombat

iwombat

Captain
Joined
Jul 12, 2006
Messages
3,767
Re: 150 Intruder Compression Check

Throttle open or closed makes no difference, really. Compression occurs after both the exhaust and intake ports are closed. I've seen it here posted a bunch of times that those 6-ers have low compression normally anyway - but not that low. Is there particular reason you're checking compression - like poor idle?
 
J

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,174
Re: 150 Intruder Compression Check

The first test on my V6 showed 30 psi, a new guage showed 65psi, a quick decarb jumped it up to 70+ , a more thorough decarb got it to 80+ , adding startron to fuel has it now at 85-90 , it runs good.
Unless you're the original owner its impossible to know how it was really treated.
 
J

jigs1950

Cadet
Joined
Oct 14, 2008
Messages
6
Re: 150 Intruder Compression Check

I'm the third owner, have no idea how it was used. VRO oil has been disconnected the pervious owner wanted to mix his gas by hand. I'm hoping it will straighten out when I can do a good decarb at the lake. Motor is mounted on a motor stand in my garage, i'm trying to find a used boat to put it on.
 
J

jigs1950

Cadet
Joined
Oct 14, 2008
Messages
6
Re: 150 Intruder Compression Check

Where do you find startron?

Thanks everyone for your input, much appreciated!!
 
J

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,174
Re: 150 Intruder Compression Check

My mechanic sold me a bottle of Startron for $12,
west marine has it for a bit more.
It won't work as good as seafoam, it just keeps it clean ,
whereas with the seafoam you can actually see the carbon coming out in the exhaust water, it looks greyish.

Try spraying some seafoam right on the pistons and rings.
It really gets the crud out.

I hired a $60 hr mechanic from craigslist to come over and walk me through the engine/installation , I'm familiar with 2 bangers but not V6 marine types, it was money well spent as he straightened a lot of issues out in 3 hrs and I learned how to set carbs etc.

red sox just won, weehoo.
 
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