1989 Evinrude 150 Compression

[111torrance111]

I have a 1989 150 HP Evinrude that I just purchased, the compression is between 75 and 80 Lbs on eack cylinder. What kind of performance can I expect and what should the compression be?

The motor starts up nice and stays @ 1000 rpm's, doesn't smoke. I won't be able to try it under a load for another two weeks.

Thanks for your help.

Jerry

 

[kenmyfam]

Re: 1989 Evinrude 150 Compression

Should be over 100 psi and within 10% of each other. Try it with a different compression tester for comparison.

 

[emdsapmgr]

Re: 1989 Evinrude 150 Compression

The compression is a little low. Sometimes the compression will decrease with age if the ringsets get carbon in the piston ring grooves. You can run some Bombardier Engine Tuner through the engine to clean out these carbon deposits and see if the compression comes up any. If you see that it does, a second application does not hurt.

 

[111torrance111]

Re: 1989 Evinrude 150 Compression

Apparently the motor was rebuilt late 2008 and only ran for about 1 hour, when I purchased the boat thay instructed me to finish the break-in period for another 8 hours. When the engine was rebuilt the replaced only one piston, but intalled new rings on all the pistons.

Do the rings need to be broken in properly to seat correctly, if so I assume the compression would increas after the break-in period. Does this sound right?

And thanks again for your help, this site has been great when it come to boating advice.

Jerry

 

[trendsetter240]

Re: 1989 Evinrude 150 Compression

Apparently the motor was rebuilt late 2008 and only ran for about 1 hour, when I purchased the boat thay instructed me to finish the break-in period for another 8 hours. When the engine was rebuilt the replaced only one piston, but intalled new rings on all the pistons.

Do the rings need to be broken in properly to seat correctly, if so I assume the compression would increas after the break-in period. Does this sound right?

And thanks again for your help, this site has been great when it come to boating advice.

Jerry

Yes the compression will come up when the rings seat. You are starting off very low for a newly rebuilt engine...that might just be the compression tester you have.

My 70hp rude had 125psi in the first 1hr of runtime after rebuild. After 10-20 hrs it was up to around 135psi.

Remember to run double oil during the break in process.

 

[111torrance111]

Re: 1989 Evinrude 150 Compression

Thanks,

I won't be able to test under a load for a couple of weeks, but after I do I'll retest with another compression tool.

Jerry

 

[df2k2]

Re: 1989 Evinrude 150 Compression

If the motor you recently bought was sitting for a couple years, then I believe that low compression should be expected. Since you say the motor was run for only a short time after rebuilt, then definitely even compression should be expected.
I have a 1987 Evinrude 200, that was rebuilt 3 years ago, and until I received it, it was never run. I had to replace alot of the wiring, the magnets under the flywheel had slipped. Needed a new powerpack, a carburetor, and a few mechanical parts as well. It also needed a new lower unit. Thermostats, waterpump, obviously.. The compression was even, but low. I want to say the compression was between 70 and 80 when I got it..

We put almost $2k into this motor -- thankfully, the motor was given to us for free.
Anyway, it works perfectly now. I haven't bothered testing the compression to be honest, but the 20ft mako it's on goes over 40 mph.
Goodluck.

Oh yeah -- take out the spark plugs and squirt about a teaspoon of oil in each cylinder. Compression should increase by this alone.

 

[emdsapmgr]

Re: 1989 Evinrude 150 Compression

It certainly makes sense that the compression would be low if it is not broken in yet. In 1989 OMC made two different 150 engines, the basic model and the XP/GT model. The XP/GT models were the high performance models and had factory high compression heads and large carbs. You can tell which model you have by checking the model number on your serial plate. The high performance models were designated by an "S" behind the model number, such as "150S." All the S models had higher compression heads/large carbs and made 165 hp at the crank, compared to the basic 150 models. The type of head on the engine will determine what compression you can expect when the engine is broken in. The basic models will probably be in the 90-95 lbs range. The XP/GT models could be 10-15 lbs higher after break in.

 

[111torrance111]

Re: 1989 Evinrude 150 Compression

Now that I've had a chance to run the motor under a load and retest the compression I have around 90lbs in each cylinder.

I have since been told that they do make a "Low Compression" engine for this year & HP as stated by "emdsapmgr", whent running the motor it ran great at both high/low speeds. I have no further complaint and agan thanks everybody for the input.

When somebody first told me they made low compression engine I thought they were crazy, but sure enough they did and it workd just fine....

Learn something new everyday.

Jerry