Good compression?

[ryanr623]

I just bought a boat (see sig). The dealership always checks them out before selling them. The engine is a 4.3 mercruiser. Compression seems good an even on all cylinders, however I've only ever done compression readings on two strokes. I know that 130-150 is good for 2-strokes.... is it the same for 4 strokes? Here are the compression readings:

1: 140 psi
3: 140 psi
5: 140 psi

2: 145 psi
4: 145 psi
6: 140 psi

 

[Don S]

Re: Good compression?

Nothing wrong with that compression.

 

[ryanr623]

Re: Good compression?

Nothing wrong with that compression.

Thanks. I'm assuming 130-150 holds true for four strokes as well then?

 

[Don S]

Re: Good compression?

http://www.boatfix.com/merc/Bullet/97/97_25.pdf

 

[Bondo]

Re: Good compression?

Thanks. I'm assuming 130-150 holds true for four strokes as well then?

Ayuh,... Pretty much Any gasoline powered motor runs above 100psi, 'n below 200psi...

 

[ryanr623]

Re: Good compression?

Ayuh,... Pretty much Any gasoline powered motor runs above 100psi, 'n below 200psi...

OK, i mis-spoke, is 130-150 optimum

Edit: nevermind, just saw the link, thanks!

 

[HT32BSX115]

Re: Good compression?

I just bought a boat (see sig). The dealership always checks them out before selling them. The engine is a 4.3 mercruiser. Compression seems good an even on all cylinders, however I've only ever done compression readings on two strokes. I know that 130-150 is good for 2-strokes.... is it the same for 4 strokes? Here are the compression readings:

1: 140 psi
3: 140 psi
5: 140 psi

2: 145 psi
4: 145 psi
6: 140 psi

Good compression......


However, if you live where you experience freezing temps, I would insist on a cooling system pressure check!!