What do you think of these compression numbers

Mercury 1992 Black Max 135, checked compression last night and it was 90 on all 6 cylinders. The motor runs great and it will throttle up fast with no load in the driveway with the muffs on but I have no hole shot and the motor is very boggy under load. Do you think the lower compression is causing this? I thought if all the cylinders were close I would be ok compression wise. Is it worth cleaning the carbs to see if my hole shot will improve or am I looking at a re-build?

Re: What do you think of these compression numbers

Yes, your compression is "LOW"...I would of preferred it above 110lbs. The good news is that with the numbers being even the engine appears to be well looked after. the lower compression would definetly be a cause for the terrible "hole shot" providing that your WOT rpms are within the recommended range with your existing prop (and pitch). I would recommend you rebuilding the engine and carbs, you would probably be amazed at the power difference compared to it now!

Re: What do you think of these compression numbers

Powder - White has recommended a radical course, at this moment. Compression gauges are often inaccurate. As long as the compression is even, the motor is very likely healthy.

Throttle up in neutral proves nothing, and can blow the motor. Cleaning the carbs is a real good idea. Also check the link and synch.

What pitch prop do you have? What kind of boat? If the prop pitch is too great, holeshot will suffer.

Re: What do you think of these compression numbers

Thanks Chris, I was sort of thinking that too. My gauge was a 20 dollar special and I think that if all the cylinders are the same that I am going to stick with it. I have lots of machines with 2 strokes and I haven't had one that slowly died yet. It seems everything else I have (snowmobiles, dirt bikes, chainsaws, etc.) work great until a sudden kaboom!

I am running a 15 pitch Solas four blade prop and it is on a 93 18 foot Maxum bowrider. It is a heavy boat!

I put in a clear fuel line over the weekend and I think the poor girl is starved for fuel. The fuel line past the pump was never more than a 1/4 full. I will be re-building the fuel pump but it was almost as if there was some sort of vapour lock limiting the fuel to the pump. I will replace all lines and the bulb, fittings and see what happens.

I like looking at all the cheap fix items first and then work into the major components.

As for the link and synch what should I be looking for? I really think I have a fuel delivery problem and to be honest I know very little about the link of synch or what to be aware of?

Re: What do you think of these compression numbers

Thanks Chris, I was sort of thinking that too. My gauge was a 20 dollar special and I think that if all the cylinders are the same that I am going to stick with it. I have lots of machines with 2 strokes and I haven't had one that slowly died yet. It seems everything else I have (snowmobiles, dirt bikes, chainsaws, etc.) work great until a sudden kaboom!

I am running a 15 pitch Solas four blade prop and it is on a 93 18 foot Maxum bowrider. It is a heavy boat but I am only getting about 2000 rpm's for the first 5 - 10 seconds of my hole shot or at least until I get on plane.

I put in a clear fuel line over the weekend and I think the poor girl is starved for fuel. The fuel line past the pump was never more than a 1/4 full. I will be re-building the fuel pump but it was almost as if there was some sort of vapour lock limiting the fuel to the pump. I will replace all lines and the bulb, fittings and see what happens.

I like looking at all the cheap fix items first and then work into the major components.

As for the link and synch what should I be looking for? I really think I have a fuel delivery problem and to be honest I know very little about the link and synch or what to be aware of?

Also the motor seems low, would bringing it up help or hinder a hole shot? It is the lowest it can go right now.

Re: What do you think of these compression numbers

Raising the motor up may improve WOT performance, but probably not holeshot. You should prop her for max RPM at average load, and live with the holeshot. A 15" pitch prop should be in the ballpark, I would think.