Question about compression numbers on a 2005 BF225 ex-USCG....

Hi everybody, new member here, I have been looking to buy a 203-2007 BF225 to re-power my '93 236 Coastal, I came across a 2005 BF225 ex-USCG, they guy says that he does not know the hours but I'm sure it has a couple of thousand on it, engine looks really clean, no rust anywhere, no rusted bolts, it looks like it has been very well taken care off, starts right up, idles fine, the green light on the ignition switch stays on.

I did a compression test on it, I first let the engine warm up, then removed all the plugs and check cylinder by cylinder, compression was about 180 to 195 PSI on most cylinders, but....cylinder #5 had a bit less than 175 PSI and cylinder #4 had the highest number of them all at 195 PSI.

I know on two strokes if there's more than 15 PSI difference in between cylinders is not a good sign..but I do not know if that also applies to 4 stroke motors, any comment or input would be greatly appreciated, thanks in advance for your help.

Dan

If it has a few thousand hours on it, why would you even entertain the idea of bolting it to your boat? Unless they are giving it to you for next to nothing.

USCG motors typically get a lot of hours, but there are exceptions, of course. You need to find a Honda Dealer and get them to hook up the HDS (Honda Diagnostic System), which will tell you exactly how many hours are on the engine, engine running history, and any error codes. The compression numbers do not sound very encouraging, assumming you did it correctly, which it sounds like you did. I'd be very careful about this whole deal.

Hi Dmas,

Welcome aboard the forum. The question you are asking has several answers depending on who you talk to. There is a rule of thumb that's been around for many moons that says if there exists a difference of OVER 10% between any two cylinders in an engine, then there will be a significant enough IMBALANCE to cause concern. You are there (more than 10%) with #5 being "slightly lower than 175" and #4 at 195.

It would seem to me that you have pretty much sized up this outboard and are in a "what you see is what you get" situation. While the compression readings aren't off the charts bad by any means, that rule of thumb is there to get you to pause and assess. As in a leak down test. That will tell you why # 5 is out of range, as it were.

These babies are pretty pricey to get into fixing one and with the variable cam timing, dual intake runners and sophisticated, proprietary fuel injection system to deal with you need to go in with your eyes wide open.

I'm not an expert on these big boys but I do know from hanging out here on this forum, there are some TSB's, recalls and updates that would have probably affected this outboard and you will probably want to look into those as well. Oxygen sensors and main shaft bearing to extension housing failure are two that come immediately to mind.

Hopefully you'll get some more info from some of the others in the group. Just wanted to say hello and throw in my $0.02.

Regards,
jimmyd

As I read Jimmy's post, another idea occurred to me. I still think you need to hang an HDS on this engine and get a complete read out, but also a good decarbonization might bring the compression into specs. It is my understanding that USCG maintenance typically does not get involved in decarbonizing their outboards, so it may be a good option - use Sea Foam, or Yamalube Ring Free. Be sure to change the oil after decarbonizing.

Hey guys, thank you all for your replies, the reazon of why I entertein the idea of buying this motor is, first, it's around 4K, second it looks in incredible good condition, like I said, no rust anywhere, not even a rusted bolt on it, I have seen BF's with 500 Hs or less that look like they have been thru hell and back, I know the compression numbers aren't that bad and I know it could be that the rings are stucked from being sit for a while, or because it has just lot of hours on it, I also know that this engines can take a lot of hours and I won't put more than 60-80 hs a year on it.

I will try to see if I can get a honda dealer to stop by this guys place to hook up the computer to find out the exact history on this engine.

For $4k heck yeah I'd give it a whirl and some top engine cleaner with Sea-Foam gas. Even if it doesn't run forever, it's probably worth twice that in parts.
Good luck.

Hey guys just to give you and update, I did not buy the motor, I ended up getting a 2005 250HP E-TEC wich I'm very happy with, anyway, I had bought a Repair Service Manual on CD, wich I'm not going to be using, in case anybody wants it I'll give it to you just for $5, if interested send me a pm, it covers all BF motors from 75 to 225HP.

thanks to all who replied to my post.

Hi Dmas,
Glad you are happy. That's what is most important. I sent you a PM for the CD but whether or not I'm the lucky one, I wanted to say it is a very thoughtful and generous offer.
Thanks for making it available.

jgmo, replied to your pm.