Compression Check '05 Larson 5.0GXI

[salmonee]

I'd search and read the compression check threads and am still confused. When doing a compression check, it says to open throttle plate completely. Does this mean put the boat "F/R" thingee in the full forward position? Also there was a thread indicating that because this engine is fuel injection, you'd have to do extra step. Wasn't sure? I'm using the following steps:

1. remove all spark plugs.
2. ground high voltage lead.
3. open throttle fully and leave it open for the duration of the tests.
4. crank engine to clear excess fuel.
5. put compression tester into cylinder #1 plug hole
6. crank engine for about 4-5 compression strokes.
7. record compression reading, zero the gauge and put tester into the next plug hole.
8. repeat steps 6 and 7 until all cylinders done.
9. re-instate engine to previous glory.

 

[Don S]

Re: Compression Check '05 Larson 5.0GXI

Do you now own this boat?
I just read your previous post. You don't own it.
You need to understand, the present owner probably won't let you do the compression test yourself. If a mechanical survey is a condition of sale, it needs to be done by a certified mechanic, not a non mechanic buyer.
I know I sure wouldn't allow people off the street to take my engine apart (even just the spark plugs out) especially on a MPI engine.

 

[salmonee]

Re: Compression Check '05 Larson 5.0GXI

I understand what your saying Don. However, i doubt that all those who had asked this question before me, was trying to sell a boat but rather buy one. I'm in a tough situation here. Initially I had schedule a place during the weekday to check out the boat. The meeting had to be reschedule to this weekend. Now I can't find a mechanic that works on the weekend! If the owner won't allow me to do a compression check, there's nothing to worry about and I learned how to do a compression check. Win...Win.

 

[superpop]

Re: Compression Check '05 Larson 5.0GXI

You can do whatever you want but I would not buy a boat without a mechanic checking it out. If the seller is willing to travel 11 hours to sell this boat then I would start out being pessimistic. Like I said you can do what you want but not getting a marine mechanic to check the boat out is like tripping over a buck to pick up a dime. On EFI motors the compression is one thing among many to look at. The last thing you want to do is drag that boat home and then discover later that some chip or sensor or pump needs to be replaced and the money you saved on this awesome deal of a boat will evaporate very fast. Find out who the local Larson dealer is in the tri cities and call them, ask to talk to the manager and tell them that you understand that they are normally closed on Sat but you will pay their mechanic time and a half to come spend a few hours and check out your boat. If the guy has any compassion he will let you talk to the mechanic who is probably twiddling his thumbs right now and maybe you can work out a deal. Start with the local Larson dealer then call all the other dealers in the tri cities that sell boats with VP drives until you find one that will step up. I think Chaparral has a local dealer there as well. You are looking at a fairly sophisticated drive system with lots of very expensive parts, so I doubt anyone on this board is going to be able to list off what you need to do as there are too many variables and if you don't do it right $$$$

 

[superpop]

Re: Compression Check '05 Larson 5.0GXI

Also, since you do not know the maintenance history on the boat and people that are willing to drive 11 hours to sell a boat are probably desperate and probably not into spending 400-500 bucks on a tune up and drive service on a regular basis, so if you do buy it then that would be my first suggestion, you will then start with fresh fluids and some piece of mind.