Bad 8.1 Horizon engine Survey

[Randy Coleman]

Hello All.

Just curious if anyone has seen this before?

While having a mechanical survey done on these twin 2005 FWC 8.1's with V drives the mechanic saw several things he didn't like.
Engines have 800 hrs on them.

1. All but 2 of the 16 spark plugs had a some amount of oil on them.
Not sludge but actual oil.

2. All compressions were between 160-175 except for 3 of the cylinders which were 130, 110,110 while cold.
The mechanic ran the boat to bring it up to temp and then rechecked the compression on those cylinders and they changed to 150, 110, 110.

The current owner runs the boat often but mostly in no wake zones so low rpm's.

I'm thinking valve job needed?
Maybe rings?

Anyone have any thoughts on this?
would Marvel mystery oil help?

any input is appreciated

 

[CaptRonn]

If you are thinking on buying this boat, I would walk away.

YMMV

 

[Pirate Lady]

800 hours not even half life yet.
Some oil on threads is not unusual.
Compression not sure about that one. Could it be so much low rpm that gunk built up on back of valves and they not sealing properly? Engines are made to run.
Very unlikely you need rings

 

[Haden]

800 hours not even half life yet.
Some oil on threads is not unusual.
Compression not sure about that one. Could it be so much low rpm that gunk built up on back of valves and they not sealing properly? Engines are made to run.
Very unlikely you need rings

Exactly, engine are made to run. Good maintenance, and run!! I have always had problems with engine that sit, or are pampered.

 

[Pirate Lady]

My son is a very good mechanic by trade. He once told me “Dad you know those shows where guys find cars in barns with low mileage and 40 years old? They are junk”. If the rats haven’t eaten everything, its all rubber-rotted, rusted, sieved up.

 

[Randy Coleman]

Thanks all for the quick replies.
I don't think we will take the gamble with these engine issues.

There's a 2004 320DA that has our name on it.

 

[Chris-380]

When I had my current boat surveyed, had low compression on 2 cyl, I told them to fix it or I am moving on. They did, very happy with that purchase. Ended up needing a heads redone

 

[techmitch]

Thanks all for the quick replies.
I don't think we will take the gamble with these engine issues.

There's a 2004 320DA that has our name on it.

Just curious, you have a 2007 320 listed in your profile?

 

[Randy Coleman]

Just curious, you have a 2007 320 listed in your profile?

Yes, We were purchasing a 2007 but deal didn't go through.
Found a 2004 that is turnkey.

 

[techmitch]

Yes, We were purchasing a 2007 but deal didn't go through.
Found a 2004 that is turnkey.

Oh, so you jinxed the 07 deal. Lol
Best of luck with the 04.

 

[sbw1]

Thanks all for the quick replies.
I don't think we will take the gamble with these engine issues.

There's a 2004 320DA that has our name on it.

Good call on the 8.1s. Likely have expensive issues to deal with.

 

[R-and-R]

FYI, I just had my ‘02 8.1s compression checked this week. 820 hours, all cylinders between 170-185.

 

[bfernald0]

Which cylinders have lower compression. If I had to guess, the cylinders toward the stern. That's the lowest point, which means saltwater has gotten into the manifolds (by running them at low rpms for extended periods). The water will hit the lowest point first and start corroding the valves.