Is a '98 305 block compatible with an '82 305

[kweir007]

I have an 82 305 Mercruiser with a cracked block and an opportunity to acquire a 98 block. Are these compatible? And does it make sense to replace the engine in an old boat, a 1982 SeaRay. I purchased it used and got shafted with the motor. I don't even know if the I/O unit is functional.

 

[TilliamWe]

Re: Is a '98 305 block compatible with an '82 305

big, you aren't a Chevy man are you? Welcome to the wonderful world of small block chevies. The blocks are compatable.

 

[Fishermark]

Re: Is a '98 305 block compatible with an '82 305

Compatible? Yes, but not quite exactly. If I'm not mistaken, the 98 will have a one piece rear main, while the 82 will not. I believe the coupler will be different for these two engines. Not a big deal if you buy the new coupler along with the new block. (If I'm wrong, someone will set me straight shortly, but at least make sure before you buy. )

 

[J.J.W]

Re: Is a '98 305 block compatible with an '82 305

also make sure it is machined for the fuel pump. Some of the newer blocks are not. Are you changing out the complete engine, long block, short block, or are you planning on putting your old internals into a different block?

 

[rbezdon]

Re: Is a '98 305 block compatible with an '82 305

I have the Chevy and I basically disagree with telliamwe.<br /><br />There is definately an issue with the rear main. I understand this drives the size of the coupler and the flywheel (11" vs. 14"???), the fit of the oil pan, and maybe even the bell housing. Also, this will change the valve covers as the heads are different, which is not as big an issue. You can swap the old heads onto the newer block too to try to save some of your old tin. <br /><br />Usually it is best to stick with the same year when changing. I guess it all depends on what your getting with the 98 block (short, long, starter fly wheel, coupler, fuel pump, and tin). I am not sure but there may be an issue with the intake manifold bolts (the center two on both sides) if you use the newer heads but I could be wrong. The exhaust should be OK.<br /><br />by the way, I think I read about the flywheel issue on a posting on this site a few months ago. A little time with the search function may get you a better answer.

 

[TilliamWe]

Re: Is a '98 305 block compatible with an '82 305

vatter disagree all you want, but if you know what you are doing, they are compatible. Actually you are correct, a 1998 "short block" would be better than just the bare block. I kinda assumed a short block, cause I was thinking, "who's gonna put 1982 crank, pistons, and cam out of a cracked engine into another block?" So if that's what you are considering, bigsplash, then this is one time where chevy interchangability lets you down. The engines changed to one piece rear main seals in 1987 (correct?) and I don't think you can even put the old two piece rear main seal cranks in with out machining, right? As far as the heads, yes, the center two intake manifold bolts changed in 1987 also, requiring a specific intake manifold, but they are available aftermarket too. However, 1982 heads will bolt right on to the 1998 block. (in fact 1955 heads will bolt on).<br />So a better fit for you would be to stay withing the years of say about 1982 thru 1986, if you are just buying a bare block.<br />Or look on here & at dougrussell.com and see the plethora of remanned & even new short/long blocks out there. And if a short/long block is in your future, get a 350 to replace that 305!

 

[rbezdon]

Re: Is a '98 305 block compatible with an '82 305

Well till, I think we agree after all just disagree in exactly what was descirbed in the original post. I know the heads swap but thinking like a relatively inexperienced wrench, I assumed he would be swapping more like a long block, in which case the intake, tin and flywheel/coupler are all issues making it not a drop in fit. All of these issues are definately things that can be resolved with the purchase of a few aftermarket parts but I got the impression he was "getting" this new block (for next to nothing) and wanting to just drop it in. The fuel pump could be issue depending on where the block is coming from (marine, auto, truck). Sorry if you did not like my answer but I think the real issue is the level to which the compatibility is compared and the really experienced guys can mix and match from experience to make things compatible where as the less experienced guys look for drop in fit.

 

[Bondo]

Re: Is a '98 305 block compatible with an '82 305

but I think the real issue is

What I see as the Real Issue here Is,.........<br />You're Both Quite Right,...........<br /><br />It's in How we read the Question,......<br />

I have an 82 305 Mercruiser with a cracked block and an opportunity to acquire a 98 block . Are these compatible?

When I 1st read this,.... I was in 100% Agreement with vatter41,.......<br />You're Not going to take an 82 Engine,+ Replace the Block Casting with a 98,.... And have a Running Engine,....<br />And like You said,....... Who would Want to,...... A 350 is a Direct Drop in(sort of),...... And are Probably Cheaper as Crate Motors.............<br /><br />Now,..... If he's swapping Motors,........Not Blocks,.........<br />TilliamWe is Right,.......<br />With some Mixing,+ Matching,.......Very Doable,.. But there Will be Glitches,... <br />All the Bolt Holes Won't be where they're Supposed to be...........

 

[rbezdon]

Re: Is a '98 305 block compatible with an '82 305

Thanks Bondo, I think the ones that will cause the biggest problem are the flywheel and coupler. It will cost a few hundred to fix this issue. Lets see what the original poster bigsplash has to say about what he actually has.

 

[whywhyzed]

Re: Is a '98 305 block compatible with an '82 305

there are no couplers for stringers that fit the newer engines.

 

[Bondo]

Re: Is a '98 305 block compatible with an '82 305

Originally posted by hystat:<br /> there are no couplers for stringers that fit the newer engines.

It Says Mercruiser,hystat,.......<br /><br />NAPA sells the Old style coupler with the 3" bolt pattern, for updating the engine with the Pre-Alpha drive........

 

[whywhyzed]

Re: Is a '98 305 block compatible with an '82 305

so it does... haha.. I'm losing it...

 

[kweir007]

Re: Is a '98 305 block compatible with an '82 305

This was my first posting and I'm overwhelmed by the collective intelligence here. I'll check on what was included in the 98' block, but there are obviously major problems if it's just the block. That gets back to my other question. Does it make sense to replace an engine, pushing the cost of the boat ($2250) + motor ($1600 for rebuilt + $600 labor) when my guy at the marina says an 82 SeaRay Seville + 302/350 motor is only worth $3500. And I don't even know if the I/O unit is good! Any wisdom on this angle?

 

[rbezdon]

Re: Is a '98 305 block compatible with an '82 305

big S, I'd keep shopping. You are at the point where you are sinking more money into the thing before you buy it than it is worth. It gets even worse if you can not do the engine swap your self. Admittedly, a good wrench could do the job just fine but the added costs for a good wrench will make your hole in the water even bigger. If you like and can do heavy engine work, then it might be OK but expect to work on it as much as you ride in it.