531 head inspection in boat what to look for

I found a boat engine with a 531 head. I can pick up the entire engine pretty reasonably and I'm curious as to what I should look for. It looks great from the outside. Guy doesnt want me to take manifolds off. It runs great he says but the boat is rotten. Can I use the rest of the engine? Also how can I tell if it is a 2.5l? Boat cam any good?

Thanks in advance,
Jon

Corrosion in exhaust port #4

jjona5 said:

I found a boat engine with a 531 head. I can pick up the entire engine pretty reasonably and I'm curious as to what I should look for. It looks great from the outside. Guy doesnt want me to take manifolds off. It runs great he says but the boat is rotten. Can I use the rest of the engine? Also how can I tell if it is a 2.5l? Boat cam any good?

Thanks in advance,
Jon

Click to expand...

Hi,

If you have a aq151 (2.5l) it will have "b230" casted in the block. 2.3 versions are based on the b21. It will probably also have a V camshaft which is nice for a oe camshaft.

They put the boat motor number on the block riveted on right by the starter. Look for that number say aq125 or aq131 or aq151 or ?

The aq151 and the aq250 are the 2.5L 8v redblock boat motors.

Also my 1986 bayliner capri has a b230 block that is 2.1L. It is a aq125b. So Sjeng posting above that the 2.1L boat motors are b21's is not correct fyi.. The last letter the a or the b or the c tells you if it's center thrust or rear thrust. The A and B's are center thrust on the crank. The C's are rear thrust. The later aq250's are rear thrust also.

Just like in cars, volvo penta stopped using b21's or b23's and switched to the b230 blocks in about 1984 fyi..

Here is the penta faq thread. The facts are not all correct, like it says the aq125 is the b21 block, not correct.. Or depends on what year the aq125 is, later ones are b230 blocks.. Quick way to tell what block it is look at the font crank pulley, if it's the b21 pulley, then b21. If it's b230 style, then it's a b230 block...
http://forums.turbobricks.com/showthread.php?t=24675

Once you get the head off. Be sure to check it carefully for cracks around the plug threads and valve seats.

Thanks for all the tips. I found the tag by the starter but I didnt see any AQ numbers on it. I took some pictures. The head exhaust port 4 was too trashed for me. I'm going to pass.

Thanks again for the help.
Jon

How cheap is the engine?

I bought a 250a which is the 151c for $100 with a blown headgasket and all of the outdrive stuff. Sold the cam for $120, flywheel for $75 and the 2.5 crank and rotating assembly are taking up space in my shed.

Boat guys will pay for the boat stuff.

jjona5 said:

Thanks for all the tips. I found the tag by the starter but I didnt see any AQ numbers on it. I took some pictures. The head exhaust port 4 was too trashed for me. I'm going to pass.

Thanks again for the help.
Jon

Click to expand...

That is actually exactly what to look for at the 151 cylinder head, there are usually a lot of corrosion around exhaust port 4 and the copper seal( ring anode) around it.