Compression test results??

[South of Heaven]

I'm not saying your engine has this problem, but a lot of times carbon build-up can give really high compression results. When this is the case the engine will often run on when shut off, pings, and generally runs like crap due to pre-ignition. Due to strange numbers, I would run the compression test again with a different gauge - something is goofy.

I will most certainly run another compression test, that's for sure. But to quote you I didn't have any "issues at all with the engine running when the key was shut off, pings or generally runs like crap". As I said before it only sounded different or "off" when running around 2k-2.5k RPM. AND also when at those RPM's it would still chug along; no stalling at all. I actually ran it at that RPM for a while to see what would happen.

 

[South of Heaven]

SEA3PO: Just curious, when you had trouble with your Yamaha 40 carbs after storing, were you draining the bowls or just running it dry (which leaves a bit of fuel in the bowls).

South of Heaven: Yes, the bottom screw is a bit less convenient to get to than the top three. I don't remove anything else. I can't remember what I use now, but it was just some small tool that I could fit in there. Nothing specially bought or fabricated. After running the engine out of fuel you basically only need a bit of paper towel to catch the fuel - or at least it's not a large amount on mine.

I didn't have a compression test on my engine (it only had 50 hours and so I focused on getting the maintenance base-lined and the carbs just so). But.... I vaguely remember that one was "supposed" to do a leak-down test if one wanted to know the compression. I think (?).

Gotcha, TY.

 

[hardee]

I would second what Marc said. Get the carbs synced and linked. That balances them so they are all working the same, and will help them to run smooth through the whole range.

I'm not a mechanic but that is what my Yami mechanic does and it works.

Harvey
SleepyC :moon

 

[South of Heaven]

***UPDATE***

So I brought the boat to a well recommended Yamaha shop that has 2 Yamaha master techs in the shop.

http://atozboatworks.net/

I told them my concerns and symptoms and they started their plan of attack with a compression test and leakdown test.

Good news: The compression was like 205 , 205, 207 and 212. Or something like; I can't remember the numbers exactly. They said it was fine.
The leakdown results were between 3-6% and they said that was also of no concern.

The BAD news: It is only running on 3 cylinders but they are 95% sure that all my issues are fuel related. They are gonna do a full carb cleaning and rebuild. When they were inspecting the different components, they also noticed that the fuel pump needed to be replaced. They said that "the diaphragm was actually disintegrated". That could also be a major player in my fuel issues and they're gonna replace it with an OEM Yamaha pump.

SO.....Long story short. My motor is good overall but needs some TLC. In the back of my mind I had always planned for this scenario anyways, so it wasn't a huge shock. I bought the boat sight unseen and w/o a pre-purchase inspection. I'm glad that I found a competent shop though. These guys are great and have been very helpful, knowledgeable and professional....but not cheap! Lol

 

[Sunbeam]

Sounds like you are on the right track now. I think you'll be really happy with the four rebuilt carbs (plus whatever else they determine is needed). I have drained my carbs religiously since they were rebuilt and that has kept them in fine fettle.

 

[South of Heaven]

Sounds like you are on the right track now. I think you'll be really happy with the four rebuilt carbs (plus whatever else they determine is needed). I have drained my carbs religiously since they were rebuilt and that has kept them in fine fettle.

I think I'll be happy with the final result as well....BUT for the past few weeks I've been researching re-powering options! I narrowed it down to the Yamy F75, Etec 75 and Tohatsu 75 TLDI. I'm more than happy that re-powering is now on the back burner for me.

Just for the sake of argument though...I was leaning heavily towards the Etec! Love the weight, less maintenance and higher torque. Evinrude is also offering a "free rigging" incentive right now until June end.

My second choice was the Yamy 75. I was told I could reuse my current rigging too.