Compression Test Results

[hdl]

New to the forum but have been reading post since I bought my boat. My motor is a 1999 built Mercury 2.5 liter 2 stroke 200 hp. My question is how do these results look;

Cold Crank Compression test
120,120,122,115,118,117

Operating temp test after 10min on water hose
116,117,123,112,115,112

Should I be concerned about the 123?

Thanks

 

[Fuzzytbay]

Re: Compression Test Results

I'd take out the plugs, spray "Deep Creep" into all the holes, tilt up the motor,
turn the motor over a couple times, re spray, and let her sit over night, then in the am, I'd put the plugs back in, fire it up, then do a retest. You might have some sticky rings.

 

[hdl]

Re: Compression Test Results

Thanks fuzzy will try. The reason I ran comp test is I have 2 issues. 1 is boat won,t idle consistantly. After about 3 to 4 minutes of idle on the water it slowly loses rpm until it dies but will idle forever on a water hose. 2 I have about a 2 second hesitation when I go from idle to wot? I have replaced bulb and line, both fuel filters, and cleaned the carbs (they looked fine as I cleaned them). Do you think the sticky rings are cause or do you have any other suggestions? Thanks

 

[JB]

Re: Compression Test Results

There is nothing wrong with your compression. It meets or exceeds all criteria.

If it ain't broke. . . well, you know the rest.

I would look for a sticking stator and possible weak fuel pump.

 

[Alvarez]

Re: Compression Test Results

Don't do anything your compression is perfect as is...

 

[Toxarch]

Re: Compression Test Results

My merc manual says numbers within 15 psi of each other on a warm engine means all is good with the compression test.

 

[Bifflefan]

Re: Compression Test Results

2 I have about a 2 second hesitation when I go from idle to wot? I have replaced bulb and line, both fuel filters, and cleaned the carbs (they looked fine as I cleaned them). Do you think the sticky rings are cause or do you have any other suggestions? Thanks

1st: compression looks good.

2nd: sounds like a carb rebuild may be in the near future. or the timing may be a tic off. there or no acclerator pumps on a 2 stroke so there may be a bit of hesatation if you slam it from idle to WOT. i dont know, as i cant do that with out fliping over backwards. as for shooting a little creep in there, it wont hurt anything.
Also, idle in the water and out are not even close to the same. it needs to be in the water for an accurate test. on the hose really donest tell you alot for the idle problem.

 

[j_martin]

Re: Compression Test Results

Before you do anything, check yuor link and sync. Especially look at the throttle pickup point, and the idle timing.

Slightly low idle speed will eventually load up and die.

Early throttle pickup will often cause a bog on the hole shot. It's a pretty critical adjustment.

If that's good, then go for the carbs.

hope it helps
John

 

[j_martin]

Re: Compression Test Results

Before you do anything, check yuor link and sync. Especially look at the throttle pickup point, and the idle timing.

Slightly low idle speed will eventually load up and die.

Early throttle pickup will often cause a bog on the hole shot. It's a pretty critical adjustment.

If that's good, then dog it and give the primer bulb a little squeeze when she wants to die. If it helps, look for an air leak in the fuel lines before the engine, or the fuel pump, or both. If it doesn't, go for the carbs.

Decarboning never hurts anything.

hope it helps
John

 

[hdl]

Re: Compression Test Results

Thanks for all the input.

Lync and sync is where I thought I would go next. I'm not familiar with timing adjustment but have a neighbor who is going to look at it with me this weekend. Will give him your suggestions "Martin".

I have tried squeezing the bulb and did not affect motor slowing giving up in idle.

A little more info if it helps:

When I cleaned the carbs the manual said the limits on idle needles is 1 3/8 to 1 5/8 turns out(if I remember correctly) I found the middle carb opened approx 1 3/4. A local dealer suggested that our heat here is rough on the 2 strokes and I should try opening them up a touch more. I did this on a water hose and the idle came up a bit and sounded much more smooth. Should I be concerned with the idle needles being opened more than manual suggest? I plan on going to the lake this week end and adjusting idle needles there for better tuning.

Regarding the pause from idle to WOT:

I called the original owner and he said he thought it has always had a slight hesitation. It's not that I dog my motor but I know this because my kids wanted to learn to ski and this required me to do this. Am I asking to much of my 10 year old motor maybe? I can live with it but I guess I am a bit picky on motor perfomance is why I am trying to correct.

Sorry if some of this info is redundant or unimportant but I'm a bit of a novice when it comes to boat motors.

thanks again.