1984 starcraft islander

havoc_squad

Senior Chief Petty Officer
Joined
Mar 5, 2011
Messages
738
Finally got around to doing a compression test on the engines. I don't think it looks good but I'm not an engine expert.

Left
1= 100
3=75
2=110
4=90

Right
1=75
3=90
2=80
4=80

Based on those numbers, looks like the left engine on the port side cylinders overheated at some point.

You may be fortunate if they sat around forever without being ran and some aggressive decarboning may help to free up the rings but I doubt it.

If you want a real picture of where things are at without removing anything yet, you would want to get a leak down tester and do a leak down test before disassembling anything.

There's only three places the air can leak out from (the block/crankcase/head, exhaust, or cooling system).

What everyone who actually knows (fastbullet & racerone and a few more) will likely say is at least the bypass covers need to be removed for inspection of piston wall and piston rings.

More likely though the head has to come off and bypass covers to get a full picture.

Take lots of pictures and label them properly on where they are from.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,534
Try some ring free, then get them running and then test
 

jdvasher

Petty Officer 1st Class
Joined
Jul 10, 2019
Messages
370
Finally got around to doing a compression test on the engines. I don't think it looks good but I'm not an engine expert.

Left
1= 100
3=75
2=110
4=90

Right
1=75
3=90
2=80
4=80
I'm not exactly sure what engine you're running but I'm assuming a Chevy 5.7 from my personal experience and what I've read along the way 100 PSI is pretty much the bottom for most engines. You lowest shouldn't be less than 70% of the highest.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,813
This boat has a pair of 90 HP outboards.-----I would remove bypass covers on the 75 PSI cylinders.
 

airshot

Vice Admiral
Joined
Jul 22, 2008
Messages
5,080
Might pull the plugs an give each cylinder a shot of storage oil before turning it over.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,813
I can't grab a hold of those engines.----Some simple inspection on your part is needed.
 

havoc_squad

Senior Chief Petty Officer
Joined
Mar 5, 2011
Messages
738
Would this be worth picking up? I think it should cover my engines.

View attachment 377212

For marine use, those after market ones are only good for fire starting (garbage), avoid if you don't like regretting purchases and having to buy twice.

Buy the factory service manual instead. Easily available via Ken Cook for legal printed reproductions or sometimes they are available via E-Bay.

Search for it by the transom bracket tag model number.

You can do a search on E-bay with the manual's part number to see if they have an original print, which usually is cheaper.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,534

Neschenbrenner

Petty Officer 3rd Class
Joined
May 10, 2020
Messages
76
Any tips on getting the gas tank out? I'm really struggling. Lol. I tried cutting around the foam and prying but no dice.
 

airshot

Vice Admiral
Joined
Jul 22, 2008
Messages
5,080
My 1983 Islander tank was replaced with an aluminum tank, also moved forward for better balance. Boy that is some ugly fuel !!
 

Neschenbrenner

Petty Officer 3rd Class
Joined
May 10, 2020
Messages
76
My 1983 Islander tank was replaced with an aluminum tank, also moved forward for better balance. Boy that is some ugly fuel !!
Think I should put this tank back in? What kind of modifications can I do when I start putting her back together for better performance?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,813
You will like the performance of that boat with 2 sweet running 90 HP motors.----Or once motors have proved themselves you could look into making them into 115 HP each.
 

Sharpie223

Petty Officer 2nd Class
Joined
May 24, 2021
Messages
163
If it was me, I'd pressure test that tank. If it held pressure then I would clean up the outside, and then figure out a solvent for the inside, using it until it ran mostly clear. What material is the tank made from?
 
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