compression Chrysler 75Hp 1972

[Fuzzz]

Hi all,
I'm french so sorry for my poor English.
I'm buying a 4,5m Rocca Century (1971) with a Chrysler 75HP.
Could you tell me what is the compression for each cylinder that i aske the seller which is a Professional to check.
It could be a good information for me to know is the motor is out or good.
Best regards

Guillaume

 

[Nordin]

Re: compression Chrysler 75Hp 1972

As new it should have 140-150 PSI, old and used 120 and up will be acceptable.
It will run on 110 PSI too but then it has loosen power.
The most imported thing is that all cyl. are equal, not more differens then 20 PSI of each.

 

[Fuzzz]

Re: compression Chrysler 75Hp 1972

Yes i know that it's important to have comparable figures on each and iknow that results are different with motor cold and warm.
Thank you for your answer.

 

[foodfisher]

Re: compression Chrysler 75Hp 1972

Different compression testers will have different readings also. Most important is that the readings are close to each other.

 

[jerryjerry05]

Re: compression Chrysler 75Hp 1972

The results need to be close.
5# difference is ok.
If my cylinders had 20# difference between them, I'd be freaking out.
Then I'd start looking for the problem!!!
20# could be a carboned up cylinder, or a bad head gasket?
Nothing I'd buy!!

 

[MickLovin]

Re: compression Chrysler 75Hp 1972

For a reference for you, I have a 1980 75hp Chrysler Skier, it's compression is 130psi on all cylinders, after having an outboard that was a 1984 model suzuki 115hp, it had 115, 115, 125 and 110, it was hard to start and didn't have the power it should have had for the size motor it was. After decarbing it several times the bottom cylinder did come up to 115, but it is really a %, any more than 10% difference is not good, most makes specify what percentage is out of spec. my suzuki was 15% difference. Hope this helped, I love my older Chrysler its a better motor than the 1984 suzuki would ever have been.

 

[Fuzzz]

Re: compression Chrysler 75Hp 1972

Last week i just have my licence to drive the boat on rivers :joyous:
I don't test the compression but it starts at the first key turn.
I try it with 6 personns on board and the boat arrives to 26knots (51km/h)
it turns perfectly and i'm very happy.