Cylinder Compression

[1954jwt]

I am about to purchase an 1988 Bayliner with a 85HP Force. The current owner is having the motor professionally tuned and compression checked before I purchase. I was wandering what should I expect the compression to be to feel safe in purchasing this boat? Thanks for your help. Jim T

 

[roscoe]

Re: Cylinder Compression

First off, YOU should have it checked.<br />Also have YOUR mechanic check the lower unit, the stator output, and the rectifier.<br />What good is it if he has it checked and lies to you about the results?<br /><br />Compression should be well over 100, preferably 120+ , on all cylinders. There should not be more than 10 pounds difference between the highest and lowest reading.<br /><br />The motor should be test DRIVEN, in the water, under a load, carrying the amount of weight you will carry in the future. That means you will probably need to put 3 friends and a full load of fuel in it to test drive it. Test drive should last atleast 15 minutes.<br /><br />Test running the motor in a tank, or with water muffs, is not an acceptable or reliable test.<br /><br />Make sure the power tilt and trim works, if equipped. They are hard to find and expensive to replace.

 

[1954jwt]

Re: Cylinder Compression

Roscoe, thanks for your suggestions. Have had motor checked, and the cylinders all check around 140 psi. His mechanic put a new prop, fuel pump, and new battery. I gave it a test drive with four grown adults, probaly around 700 lbs, and it ran great. Comes out of the hole with no problem. I brought it home with me and looking for years of fun. Again, Thanks for your help. This forum had made the difference. Jim

 

[roscoe]

Re: Cylinder Compression

Great, glad it all checked out.<br /><br />Make sure you decarb the engine twice a year to keep her running.<br /><br />Decarb: http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016 <br /><br />Good luck and happy boating.