Buying a boat - compression test

[Crubino]

Hi there,

I am a first time boat buyer (I used to boat when I was younger) and am in the middle of a deal where it may fall through due the compression test.
boat - 2001 29ft maxum 7.4 mercruiser on it original 450 hours.

had a mechanic and boat surveyor on it today and everything was decent until the compression test... all cylinders keep coming in the range of 145-155 except for one that was around 120...

Compression test was done at the end of course after a sea trial.

I have been advised that there is a risk in this because of that low compression on the last cylinder. As experienced boaters how nervous would you be to buy the boat knowing that?

Any help would be great.

Thanks,
Chris

 

[achris]

Lots of other boats out there... Low compression could be rings, valves or the head gasket, and unless the mechanic runs a leak-down test, you don't know which it is.

I'd pass and find another boat.

Chris....

 

[tpenfield]

:welcome: to iBoats . . .

Single 7.4 engine on that boat (Right?)

That 120 cylinder does stick out like a sore thumb. I agree with Chris . . . probably best to pass, unless you are really interested in looking into why that one cylinder is 20% low.

Besides, a 29 foot boat running on a single 7.4 engine, is not a great combination . . . really needs twin engines at that size of boat. Having a weakened engine only makes it worse.

 

[tank1949]

and big block replacements/parts maybe difficult or more expensive to find? Even 350 cores are becoming like hen's teeth to find here in NW Florida.

 

[Scott Danforth]

for 2001 the motor is most likely a left over Gen VI block as the 8.1 and 8.2s were the motor of choice starting in 2001. depending on the power, it could be any one of 3 heads

a good machine shop will get about $150 for a simple head job.

if the 450 hours and 19 years was in salt water, the manifolds most likely are leaking and the valve seats could be rusty. this would indicated that you need new exhaust manifolds

realistic costs

new exhaust manifolds and elbows - $700 (you do the labor)
cylinder head needs to be re-man's - $150 in machine cost, $125 in gasket costs (you do the R&R labor)
block needs a re-ring - $1800 minimum (you do the R&R labor)

use these costs in your negotiation.

if you have to pay someone to do the work, your looking at about $1500 for a manifold swap, about $1800 for a head job and about $7k minimum for pulling the motor and work. most likely they would recommend a mercruiser reman which is significantly higher, however comes with a warranty.