Yamaha 130 V4 Project Build.

**olboatman** · 06-04-2016, 05:32 AM

Great vid! I hope the driver was OK. Your boat sounds good.... what body of water are you racing on? Would that be the Amazon River? Just curious. Gary

**rodrigokrug** · 06-07-2016, 09:29 AM

Haha, it's all OK, just a fright!

No no, I live in the extreme south of Brazil, this is a hydroelectric dam, here we have a lot of this lakes and huge rivers all over Brazil!

If you liked the sound, check it out the test from last weekend.

**Mr. Demeanor** · 06-19-2016, 08:40 PM

Had a nice ride today and when I got home the weather wa cool enough to work outside. I just turned 100 total hours and about 35 hours since the re-ring after eating the throttle plate screw. Seemed like a good time to do a leakdown / compression.

These numbers still confuse me. I just cant figure out why my port side runs 10-15 pounds higher than the starboard side. Leakdown was good with the worst cylinder at 7%.

I lost 8-10 psi when we raised the ex ports and I would like to get that back but Im afraid to cut the heads with these goofy compression numbers.

1. 140 psi 4% leakdown
3. 140 psi 7% leakdown

2. 155 psi 4% leakdown
4. 150 psi 5% leakdown

Exhaust ports are all EXACTLY the same height measured from the deck and swapping heads makes no difference. No difference in carbon buildup or anything else that would explain it. This has always been the case with this motor.

Throttle was wide open.

What else could effect cranking compression? I wouldnt think the crank rotation would be fast enough to matter. I would think crank rotation would help pack air into the starboard side anyway and thats the low side.

Im tempted to pull off the intake and do a compression test just to see if something there is making a difference.

**baja200merk** · 06-19-2016, 10:30 PM

Deck height is different port to starboard.

Whats squish?

**Mr. Demeanor** · 06-19-2016, 10:51 PM

Originally Posted by baja200merk

Deck height is different port to starboard.

Whats squish?

Deck height measured to piston and to ex port is the same. Thats what I kept looking at. Squish is the same as well.

I need to spin the motor faster and see if it changes. Maybe its not filling on the starboard side at cranking speed. I tried a running compression test once but the valves in the tester get destroyed.

**rodrigokrug** · 09-19-2016, 05:02 PM

Hey Guys!

After almost a year of preparation, finally I win the most important class in our championship. This class we call "Força Livre"(free power), that means every boat can race!

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Here is the video:

**olboatman** · 09-19-2016, 07:00 PM

Originally Posted by rodrigokrug

Hey Guys!

After almost a year of preparation, finally I win the most important class in our championship. This class we call "Força Livre"(free power), that means every boat can race!

Here is the video:

CONGRATS !!!!!

Great driving and she sounds sweet also!

Gary

**rude tim** · 09-20-2016, 06:17 PM

Have you tried doing a compression test by firing the motor? I have done it and know a few others that do it also. As soon as it fires shut it off and look at the numbers. If you have duel plug heads make sure you remove the other plug wire. Lol

**Mr. Demeanor** · 09-20-2016, 08:28 PM

Originally Posted by rude tim

Have you tried doing a compression test by firing the motor? I have done it and know a few others that do it also. As soon as it fires shut it off and look at the numbers. If you have duel plug heads make sure you remove the other plug wire. Lol

I have but it destroys shraeder valves pretty quick.

**rude tim** · 09-20-2016, 11:29 PM

Originally Posted by Mr. Demeanor

I have but it destroys shraeder valves pretty quick.

Are the numbers closer when taken by firing the motor? They should be.

**Mr. Demeanor** · 09-21-2016, 10:20 AM

Originally Posted by rude tim

Are the numbers closer when taken by firing the motor? They should be.

Yes, I think I posted them somewhere back in this thread.
Next time I have the intake off I will do a test just for curiosities sake. I should probably pull it off for a look at he reeds before the fall Suwanee river run.

**Umassot50** · 09-22-2016, 09:29 PM

Where are the ring gaps? The lower compression side could be exposing the ring gaps if the piston is rocking away from the ring gaps due to rod angularity.

Due to the nature of an outboard V motor one bank will be thrusting againts the exhaust side of the cylinder on the compression stroke and the other bank thrusting against the intake side of the cylinder.