Compression for 340 Monsoon

[TomMcCauley]

Hi all,

Looking at purchasing a 04 VLX with the 340 Monsoon engine. Compression checks all came back at 160 - 165. Can someone tell me what the good range is? I can't find anything online that tells me what this should be.

Thanks!

[Lance B. Johnson]

Consistency is key here. According to the book that came with my snap on gauge, you should take the highest reading and multiply by .75 to get the acceptable low reading. I'd say your fine based on the info you posted. Also if someone else post " well my 340 monsoon gets 180..." doesn't matter. The variance can be if the test was done hot vs cold, 3 cranks vs 4, throttle plates open vs closed etc.

[Woodski]

A tight spread as you indicate is a good sign. The variation in test process can be very significant as noted, # cranks, hot/cold, thottle plate open/closed, type of gauge etc. Another test would be a leak down test which will tell you where any leakage might be going and is really a better test for engine health.

[Indyxc]

A tight spread as you indicate is a good sign. The variation in test process can be very significant as noted, # cranks, hot/cold, thottle plate open/closed, type of gauge etc. Another test would be a leak down test which will tell you where any leakage might be going and is really a better test for engine health.

Yeah the variation is key.

When I bought my boat, I did a compression check with the Monsoon 340. With the gauge I used, all cylinders were around 200-210 psi with the throttle open, lanyard disconnected, and about 4-5 cranks.

[TomMcCauley]

Yeah the variation is key.

When I bought my boat, I did a compression check with the Monsoon 340. With the gauge I used, all cylinders were around 200-210 psi with the throttle open, lanyard disconnected, and about 4-5 cranks.

Thanks all! Great info. Now, I am also looking at another boat with a Hammerhead engine. What do you all think.....Hammerhead 375 or Monsoon 340? I assume the 375 is going to use a little more gas but have more power, but I don't know a lot about reliability between Monsoon vs. Hammerhead, how it might, or might not, have any bearing on the wake, etc. Sorry, but I'm definitely not well educated in this area. I've got the Monsoon 325 on my current boat and have had really good luck with it.