offthefront

I might be changing out one of my 89 454 mags ...Jury is still out but looking like that is what I will have to do ..... I got a price of 4276 from Jasper and and about 5500 from Mercruiser ... any other suggestions ?

gmhdfan

Why not rebuild what you have? Is the Hardware broke? Just seems like you could freshen up both motors for that kind of money.

deboatmon

Now is the time to upgrade in cubes. More cubes = less RPM @ cruise speed = generally less wear and tear and noise.

There are still plenty of good used complete 502EFI's around if you know where to look and they are reasonably priced.

The change from a 454 to 502 is nice. The EFI is smooth and easy to operate. It's a drop-in.

It's easy to make more power with your 454 but it will require more RPM. I've built several over the past twenty years. No more. It's cubes for me.

I see you're looking at only one engine, but the other can't be too far behind.

Just my $.02 worth.

offthefront

Actually both motors have less then 20 hours ...This motor got hot and (SeaPump) and we haven't found the source of water Intrusion ...yet ....

deboatmon

I guess I'd be looking at duplicating the other motor under those circumstances.

Only 20 hrs ! That really blows big time.

Good luck and I hope you get going soon for the summer ahead.

p4-33

Motor got hot... Sea Pump... bummer.

I'd take a look at the heads. The Merc cast heads don't handle overheating very well, and like to crack around the valve seats. I've done this two separate times after loosing alternator /circulating pump belt.

The bad news... if cracked, the head needs replacing, as it's not fixable. If water ingestion was minimal, and you caught it right away, your block/bearings are probably ok. It's easy enough to pull your main caps and see what kind of damage has been done, especially with only 20 hours worth of wear on them.

The good news... a new head is much cheaper than buying a whole long block.

First, try a leak-down test for each cylinder and take it from there.

Good luck,
Brian

offthefront

Thanks Brian ..we are waiting on the head test .. also if the come back ok ..we are going to leak down test the engine without pushhrods installed so we can place Pistons at bottom of Cylinder and check the block too ..One thing though ..my merc guy wants to use merc heads and they are like 1100.00 each ! .. So his theroy was to just do the whole motor ..4200 ..includes heads ....I Think I saw dart heads for 1100/pair ? ....

p4-33

Once the heads are off, it willl be fairly easy to see which cylinder(s) has water in it. Mine was easy, even before tearing the motor down - pulled spark plugs, water drained out.

Once you've narrowed down which cylinder has problems, take close look at head for cracks. Send it out for magna flux if you can't find anything with your eyes. Costs about 25 bucks or so. That way, you're sure you've found your problem.

Even going with a Merc head, $1100 is still less than $4200. Odds are in your favor that you only have one cracked head, not two. If you're looking at upgrading to Dart or something else, now you're looking at doing four heads, not just one. Then you might as well look at a different cam, bigger carb, maybe bigger pistons, longer crank and rods... it never ends. Dart talldeck block and AFR CNC aluminum heads makes for a pretty nice 565.

Good luck,
Brian

offthefront

Finally got heads back ....they are ok ....we put heads back on ..left pushrods out so we could bottom each piston and do leakdown ..leakdown is fine ...5-8% ...now what ?????? EM's check ok .....

MACDAD260

How did the head gaskets look. Any signs of leaks there? That could be all that caused the water in the oil. When the heads were checked for cracks did they check them for straightness? Maybe all you need is new gaskets. That is a cheap fix. Good luck.