compression test

[viper1]

Well since i have to pull the engine any way Decided to run a compression check. Not terribly bad as far as difference. But thought readings looked low. From what I seen it should be about 140 . Wife run after an oil can and some oil. Mine seem to have made off with the gremlins. So then did a wet test.
The Engine says 750 hours on it.

OK my readings were
Cyl Dry Wet
#1 110 125
#2 115 120
#3 115 125
#4 105 120
A little over a 10% improvement. On a car I would suspect the head with such an increase. So what do you all say. Is this worth trying to redo? I'm getting 4200 WOT but only around 25 MPH on this 22.1 Starcraft Islander. So whats your Verdict?? Replace freeze plugs and put back. Or spend money to rebuild?

 

[alldodge]

Your a little worn but not that bad for the hours. Need to do a leak down test to determine if it's valves or rings. Reaching 4200 isn't bad either with what your seeing

 

[stonyloam]

Compression checks can be a little tricky, depending on a bunch of things including the gauge. Does it smoke, is it using oil, how is the power? I think I would grab another gauge (borrow one from autozone) and recheck. The numbers look OK just a little low. We're it me, I would get her running, do a tune up (make sure the timing is correct) and run it. Summer days are too few as it is. Worry about a rebuild in the off season. That is a lot of boat to be pushing with a four cyl., 25 doesn't seem to bad. Good luck!

 

[Rick Stephens]

My 90 3.0 is 115 psi all four jugs. Seems OK if maybe a little off its rated power.

 

[GA_Boater]

Are you getting water in the oil since the crack patch? Was the compression test done hot or cold?

 

[viper1]

Well Compression test was done cold. So a little could be blamed on that. Patch remained bone dry. Going to do a leak down. But at 15-25 lbs. Can't believe people are using 100 lbs these days. Using a cylinder block to prevent cylinder roll. What about the seals? Or even valves? They aren't meant to be exposed to 100 lbs of pressure. I understand you can hear a leak at that. But man that sounds wrong.
As for smoke, I seen a couple whiffs when first started after sitting. Wrote it off to valve seals. I think a 28 year old engine would definitely have some brittle seals, from age alone. Thought about changing them while out. Maybe the head gasket too.
But i haven't made up my mind. So thought Id draw from the many years of experience here.
The man told me he did 40MPH with this boat. But after all this i have learned he knew little to nothing about boats or mechanics. Not putting him down as there are many that don't. So I think what he may of done is like others. Seen 4200 on the RPM's and took it as MPH. Makes more sense to me then that boat actually getting 42 MPH on a 3.0 I have three props he tried on this boat before this one. 2 are the same. But he didn't know that.LOL!
Seems to me at best this boat with the 3.0 L would do is 25-30 mph. I could be wrong. But speed isnt a big thing to me. As on Erie rarely see days I can run WOT or would i choose too. So 20-22 mph is good as long as boat remains on plane. And this boat did get on plane in a reasonable amount of time.

 

[stonyloam]

750 hours, well if that were a car averaging 50 MPH, that is about 40,000 miles. I think you are OK to run for the summer.

 

[viper1]

Well by my test results seems Its not in the block but the head. So could use a valve job. Not sure a rebuild at this time will help much. So for now plans are to replace the freeze plugs. Install engine and enjoy. Once boat is on the water, i'm going to install a set of 10 x 11 doors on barn. This way i can store it inside. Already have a coal stove in there. So winter work will be possible. As I will rebuild the whole engine given time. Also need room to tear up floors and redo foam and all while im at it.

 

[Rick Stephens]

On my 3.0 a vacuum gauge at idle bounces up and down hard. Can't idle below 800. Vacuum smooths out at 1200 RPM. Valve guides is my guess. The motor is 25 years old, looks never to have been worked on. With a 17 inch prop it goes about 34 MPH max trimmed juuuust so, and I better have a tail wind. Keeps on chugging though. Hard to decide to open it up. Gonna cost a bunch cause it will need everything.