Leak down test failed on new motor...what would you do?

[MikeBelter]

I have a 225 Pro XS (3B383447) I got on the new boat I bought in March and took it in because I have never been able to get more than 5700 rpms or so. Wanted them to check it out and they couldn't figure out anything since it ran great. Compression was fine but a leak down test failed. Now they're going to try a couple other things but they suspect I'll need a new head. I'm real nervous that a new head on this motor won't be the same in performance and durability as a motor without defects that comes from the factory. I don't want to get screwed with a motor that was defective from the start getting fixed the cheapest way they can get by. Especially considering how much I paid buying a new boat in the first place. Any advice?

[1Holeshot]

I suspect your powerhead will be replaced with a new one under warranty which is what a warranty is.

[MikeBelter]

Yea but is a new powerhead installed at the dealership going to be the same power, performance and durability overall compared to the entire motor that was built at the factory? I imagine that when they're put together at the factory all the tools and machines are calibrated better, along with many other factors.

[moymurfs]

The part is the part. It's from the same factory all the assembly steps and torque settings are already done. It's the externals the service dept installs. You will get a motor that performs like it should..which is more than what you have now.. Powerheads have been replaced for years by every manufacturer. If it wasn't sound the practice would have been dumped by now and motors would be 3x more expensive.

[massbays]

compression was fine, but failed a leakdown?
get a second opinion

[mactlman]

Yea but is a new powerhead installed at the dealership going to be the same power, performance and durability overall compared to the entire motor that was built at the factory? I imagine that when they're put together at the factory all the tools and machines are calibrated better, along with many other factors.

powerhead is like a long block in an auto. comes from factory almost ready to run, just needs installed and plumbed in. factory assembles it entirely other than the small amount of assembly to install it

[yam911]

What specifically did the leak down test show? Failed rings, failed gaskets, failed valve seats, or ?

If a gasket, that is a simple matter of replacing the applicable gasket. Chances of two failing at the same time is remote.

If a failed valve seat then perhaps the valve can be lapped to better fit the valve seat. Or the valve and/or valve seat replaced.

If a failed ring then perhaps a new set of rings might cure the problem.

I suspect that you are some point away from having the complete power head replaced. Which as noted is no big deal if that is what Mercury Marine tells the dealer mechanic to do.

A properly repaired motor should be as least as durable as the non repaired motor that came from Mercury Marine.

[bassfisher444]

Compression test passed but leak down failed? That doesn't make sense at all, you don't even do a leak down test if compression is good, and if a leak down test isn't done correctly when that cylinder is in the compression stroke it will fail every time.

[MikeBelter]

I'm not sure what the leak down test showed as far whether it was gasket vs. valves vs rings that were failing. The mechanic says they tested for everything else they could think of and couldn't find anything wrong so Mercury asked them to do a compression and leakdown test and as a result he said that he's pretty sure I'm going to need a new motor.

[yam911]

Something is missing. This is not making any sense.

A leak down test should clearly indicate where a motor is failing to hold the pressure that is applied to a cylinder. That is its purpose.

If all cylinders are failing the test then I would think another test from a different mechanic would be in order.

But if Mercury is willing to provide a new power head then why not jump at it? Better a six month old motor with a new zero time power head than a six month old motor with a six month old power head.

[Ranger Rod]

I would imagine Mercury has learned their lesson having mechanics repair powerheads. Better to just send them a new on. Plug n play.

[BMCD]

New power heads come dressed, if it does not go out for warranty it will be installed on a new motor for someone else.

[massbays]

That motor has Adaptive Speed Control
it needs to be propped with the diagnostic computer plugged in.
go there first before condemning anything.

[1BADAIR]

What do they consider failed? What were the leak down percentages

[EuropeanAM]

New power heads come dressed, if it does not go out for warranty it will be installed on a new motor for someone else.

That is not normally the case. SOME components (fuel rails, injectors, plugs, coils, and throttle plate) are included, but the hoses, exhaust, wiring harness, PCM, and numerous other components are usually transferred.

That being said- a properly installed powerhead on this engine should provide years of dependable service, just like the original should have.

I would be interested in what the exact numbers were on the leakdown test, more for curiosity than anything.

[MikeBelter]

I'll ask the mechanic what those exact numbers are. Mercury wants a run-down test before they authorize a new powerhead but the cable they need to connect from the computer to the engine is on backorder. Been waiting a couple weeks on that and no one knows when its coming.

[howieranger]

Did they say what a "Run Down" test is?

[massbays]

that cable hasn't changed in quite a few years. they don't have one? get a 2nd opinion.

[yam911]

A cable connected to a computer is needed to perform a leak down test???

[thommo59]

My guess is they would like to analyse the full “ run file” and this is downloaded via the Merc g3 system. I’m guessing this dealer doesn’t have or needs a new harness to perform this