Time to upgrade boats - What one should I be looking at next

[seadoosnipe]

Compression ranges for a 4Tec are in post #20. My statement above was for our 351 Windsor V8 which is what comes in Ski Nautique.

Numbers in post #20 are for a warm engine. You can expect slightly lower results on a cold engine. Compression should always be done on a warm engine (after you test ride and are considering moving forward with purchase).

Compression is a number, but not as important as what the numbers are across the spectrum. The compression should be between 125 to 135 psi, but more importantly, you don't want a large spread across those readings, in any engine. If you have a cylinder at 122, one at 134, and one at 138, then you need to build a motor. The idea is, if there is a 10% spread on ratio, then it's time for an overhaul. Now, if you have 132, 130, and 129, you should be fine.

There are 2 types of compression tests, a wet and a dry. If the engine has been sitting for a while, squirt a dab of oil in it, rotate the cylinders, then get a test. If you run it, then you'll want it to sit for awhile, to let it cool off, because you could get a bad reading.

There are a lot of articles on compression tests. They are important and interesting. They are like the heartbeat of an engine.

 

[seadoosnipe]

Should the compression on this motor be at 155?

That would be kinda high. IF you were to test it, wet, it may be that high. But, the 4-TEC's are suppose to be between 125-135 psi.

 

[seadoosnipe]

Thanks for the information, I did hear issues with the washers on the superchargers. I really want to stay under $15K if possible.

I thought I answered that one. When the 4-TEC supercharged engines first came out, they used ceramic washers, because they could handle the heat. But, they were suppose to use mineral oil in their motors. Well, Seadoo/Rotax got everyone so use to using Synthetic, people didn't read that part of the instructions. The Synthetic oils caused the Ceramic washers to come apart, and destroy the chargers, and block all the oil ports with pieces of ceramic. This has since been corrected. All washers now are stainless steel. So, chances of you getting a bad washer are slim to none.