Low Compression New SBT Engine

[ParkerMclain]

After installing an SBT reman 787 engine and going through the break-in period, I checked the compression on BOTH cylinders last night and both were reading 90 PSI. The ski starts right up in and out of water. On the water the ski does seem to bog on 0-50% throttle at times, but from a standstill, if I give 100% WOT, there are no issues and will easily run 55 MPH. Spark plugs are also black.

During the engine replacement:
- Installed a new battery
- Sent fuel injectors off to be cleaned
- Emptied both fuel and oil tanks / cleaned
- Replaced the 2 small oil lines coming from the oil pump
- New spark plugs
- New rotary valve
- New wear ring
- New impeller pump oil

Thoughts?

Compression is being tested with throttle at 100%

 

[SIMPLEARKANSAN]

Try a different compression tester?

 

[ParkerMclain]

Try a different compression tester?

Planning to try and get ahold of another one in the next few days. The low end bog / black spark plugs was just making me think more those numbers might potentially be accurate but, I do agree it’s best to confirm an accurate reading first.

 

[GGuillot]

Planning to try and get ahold of another one in the next few days. The low end bog / black spark plugs was just making me think more those numbers might potentially be accurate but, I do agree it’s best to confirm an accurate reading first.

I don't think a 787 will even run at 90 psi on compression, sounds like a faulty tester.

 

[mikidymac]

Sounds like you need to fully go through your fuel system for the bogging.

As far as compression it wouldn't even start in the water at 90 psi and no way get to 55 mph.

 

[ParkerMclain]

Update: Ran it against another compression tester, and tested 140 on both cylinders. So that solves that.

Now to sort out this spark plug fouling issue. Injectors were sent to the “Fuel injector man”. Maybe new fuel filters are next?

 

[etemplet]

Good move !! I found these when I did my first RFI. I do injectors and filters on every fuel injected ski I get.

 

[Seadoobuddy]

Was the "
faulty test from Harbor Freight.....they seem to always read about 90psi

 

[ParkerMclain]

Was the "
faulty test from Harbor Freight.....they seem to always read about 90psi

It very well may have been. Its an older gauge I’ve had for quite a while

 

[ParkerMclain]

Update:
Installed a new fuel pump along with external and internal fuel filters. Going to throw 2 new spark plugs in and hit the water today. Hopefully all is resolved

 

[ParkerMclain]

Fixed one problem and created another. The jet ski has expected throttle response at low end power, and the plugs look normal.

After replacing my fuel pump / filters, I no longer have a fuel gauge. And while riding the ski, I get a loud maybe 2 second beep once every 30 seconds - minute. No other lights are on. Ski starts perfectly. 2 beeps when lanyard is attached.

 

[mikidymac]

The beep is for low fuel. Double check the float and gauge sending unit.

 

[DanSquires]

you unplugged the sending unit when reinstalling.. i've done that before as well.

 

[ParkerMclain]

Ive also noticed this is sensitive to how the lanyard is plugged in. If the lanyard isn’t fully plugged in, I’ve been able to start the ski and have the info center but not fuel gauge

 

[BlackMagicWater]

Ive also noticed this is sensitive to how the lanyard is plugged in. If the lanyard isn’t fully plugged in, I’ve been able to start the ski and have the info center but not fuel gauge

Take your fuel pump assembly back out, there is a tan colored unit in the outside of fuel canister. Ensure it’s plugs in, or hasn’t fallen off the canister completely. I had to zip tie mine back into place on the side of the canister, fuel gauge been working like a charm ever since. Best of luck!