2.5 200. High compression

**Fishbum** · 10-16-2019, 12:55 PM

I bought a used powerhead form a member, it is a 1995 200 carb engjne
after installation on the midsection I decided to ck compression around 165 on all
dont know Know what other mods may have been done but
thinking of trying to lower that compression. Anyone know what thick head gaskets would do? Just want to sell it. Thanks

**HStream1** · 10-16-2019, 01:05 PM

Gaskets alone wont lower the compression all that much. In its current Compression condition that motor needs at least 101/102 octane. Id just look for a set of stock 38cc heads if you simply want to sell it.

**Fishbum** · 10-16-2019, 02:41 PM

Ok thanks.

**Fishbum** · 10-16-2019, 03:01 PM

Any idea what these heads had to be to get 165 compression?

**mach351** · 10-16-2019, 07:39 PM

Usually around 30cc will get you 160-170psi depending on porting and gaskets

**TEXAS20225** · 10-16-2019, 10:20 PM

i have plenty if yours are unmarked ill trade with you

**Fishbum** · 10-17-2019, 02:27 AM

Originally Posted by TEXAS20225

i have plenty if yours are unmarked ill trade with you

By unmarked you mean undamaged ? Sounds good I will remove them in am and contact you
got a phone number? Mine is 770-231-7430

**TEXAS20225** · 10-17-2019, 07:34 AM

yes undamaged!!ill be sending you the same undamaged 8176751224 im Bobby V.

**Dave Strong** · 10-17-2019, 10:14 AM

Before you start replacing parts you might want to try another known good compression tester.

Dave

**tlwjkw** · 10-18-2019, 12:09 AM

Originally Posted by Dave Strong

Before you start replacing parts you might want to try another known good compression tester.

Dave

**Fishbum** · 10-18-2019, 05:44 AM

Going with different heads. Thanks everyone

**gmorgan** · 10-22-2019, 02:09 PM

Going from 1.3 mm gaskets to 1.0 mm gaskets raised my compression seven pounds.

**Fishbum** · 10-22-2019, 02:52 PM

Ok thanks

**Aaronhl** · 10-23-2019, 02:18 PM

Originally Posted by gmorgan

Going from 1.3 mm gaskets to 1.0 mm gaskets raised my compression seven pounds.

are gaskets as simple as that or do you need special tools to measure squish, just wondering what I could do to raise my compression with simple changes

**Merc 2.5** · 10-23-2019, 08:48 PM

Originally Posted by Aaronhl

are gaskets as simple as that or do you need special tools to measure squish, just wondering what I could do to raise my compression with simple changes

Yes promarine has diff thickness for the 2.5. 1mm thinnest I think but will raise 5 or so lbs. every motor little different. But not sure u will notice a difference