1987 GM 305 x 2 rebuild questions.

acadian2022

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Good day all, several questions this morning ok lots :)
I purchased a 1987 Bayliner 2850 for the trailer for my 25 foot aluminum boat and got the boat for free not to mention the aluminum 28 foot trailer for a GREAT price.
Looking at the boat its in absolutely great shape accept the engines!
So we pulled out the 2 engines completely strip down ready to be sent to machine shop for a professional wash and owning / boring etc.

My research online shows by the serial number one block is truck block and other one is passenger block mind you the previous boat owner was not sure of the full history of the boat therefore I'm not sure if the boat came with 2 different 305 blocks originally since some online research mention its not uncommon for an engine company to send different block to boat manufacturer since most 305 are the same???

2 x 1987 GM 305 open loop for my Bayliner slat water
Engine no Serial no 14093627 heads 14102187 Engine no 2 serial no 14094766 heads same 14102187

1. Can I use reg gasket kit or not? other then brass plugs
2. 350 gasket kit work on the 305?
3. 350 lifter same as 305?
4. Oil pan of a 350 fit 305? one is dented.
5. I'm in the process of sending blocks and head cleaned and bored several forum say .40 over is the max for a 305 is that correct? its too bad out of 16 cylinders I have one that has a scuff machine shop will check if it can be bored if not I have a lead for 2 x 350 GM and wanted to know if bell housing / Crankshaft / shaft / timing chain / roter from my 305 fits a 350 engine since the crankshaft and cam are in perfect condition or I keep shopping for 305 block if the new from the machine shop is not good :(
6. 350 head bolts the same as the 305? see more availability of 350 head bolts then 305

Well that's a start big thank you too all have a great day I truly lover this boat!
 

acadian2022

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Joined
Aug 14, 2022
Messages
41
Good day all, several questions this morning ok lots :)
I purchased a 1987 Bayliner 2850 for the trailer for my 25 foot aluminum boat and got the boat for free not to mention the aluminum 28 foot trailer for a GREAT price.
Looking at the boat its in absolutely great shape accept the engines!
So we pulled out the 2 engines completely strip down ready to be sent to machine shop for a professional wash and owning / boring etc.

My research online shows by the serial number one block is truck block and other one is passenger block mind you the previous boat owner was not sure of the full history of the boat therefore I'm not sure if the boat came with 2 different 305 blocks originally since some online research mention its not uncommon for an engine company to send different block to boat manufacturer since most 305 are the same???

2 x 1987 GM 305 open loop for my Bayliner slat water
Engine no Serial no 14093627 heads 14102187 Engine no 2 serial no 14094766 heads same 14102187

1. Can I use reg gasket kit or not? other then brass plugs
2. 350 gasket kit work on the 305?
3. 350 lifter same as 305?
4. Oil pan of a 350 fit 305? one is dented.
5. I'm in the process of sending blocks and head cleaned and bored several forum say .40 over is the max for a 305 is that correct? its too bad out of 16 cylinders I have one that has a scuff machine shop will check if it can be bored if not I have a lead for 2 x 350 GM and wanted to know if bell housing / Crankshaft / shaft / timing chain / roter from my 305 fits a 350 engine since the crankshaft and cam are in perfect condition or I keep shopping for 305 block if the new from the machine shop is not good :(
6. 350 head bolts the same as the 305? see more availability of 350 head bolts then 305
 
Last edited:

Bondo

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Ayuh,.... Welcome Aboard,...... It'll be cheaper, quicker, 'n easier to drop in 2 new long block crate 350s, that to rebuild the junk you've got now,....
'm all the accessory parts off the 305 will bolt right on,.....
 

Scott Danforth

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and if you go vortec (1996+ motors), only the intake manifold must change and you get even more power.
 

acadian2022

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Ayuh,.... Welcome Aboard,...... It'll be cheaper, quicker, 'n easier to drop in 2 new long block crate 350s, that to rebuild the junk you've got now,....
'm all the accessory parts off the 305 will bolt right on,.....
Good day. Your not wrong in what you say to a certain extent however I have a good contact at a machine shop not as expensive as one may think. A new engine shipped to me in New Brunswick Canada is not as available as one may think. As for more HP I'm not interested whatsoever I'm a old guy now vs my younger days with my fare share of speeding lol. Beside I so enjoy taken something that has potential to have a bunch of us working on and one day see it actually run well. Too all please keep sending me your opinions and knowledge it's priceless BIG BIG thank you all
 

acadian2022

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Ayuh,.... Welcome Aboard,...... It'll be cheaper, quicker, 'n easier to drop in 2 new long block crate 350s, that to rebuild the junk you've got now,....
'm all the accessory parts off the 305 will bolt right on,.....
Good day. Your not wrong in what you say to a certain extent however I have a good contact at a machine shop not as expensive as one may think. A new engine shipped to me in New Brunswick Canada is not as available as one may think. As for more HP I'm not interested whatsoever I'm a old guy now vs my younger days with my faire share of speeding lol. Beside I so enjoy taken something that has potential to have a bunch of us working on and one day see it actually run well. Too all please keep sending me your opinions and knowledge it's priceless BIG BIG thank you
 

Bondo

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A new engine shipped to me in New Brunswick Canada is not as available as one may think.
Ayuh,.... Call yer local GM dealer, 'n ask them,....
It might be cheaper than you think,.......

As for the over-bore, any more than .040 leads to thin walls, 'n cylinder hot spots, which can lead to an early failure,....
 

acadian2022

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Ayuh,.... Call yer local GM dealer, 'n ask them,....
It might be cheaper than you think,.......

As for the over-bore, any more than .040 leads to thin walls, 'n cylinder hot spots, which can lead to an early failure,....
Thank you for your reply its looking like 20 over would work. As for GM dealers we only have Ford in the Maritime hahaha just kidding you have point will give them a call who knows. Let's all keep in mind I'm retired have a huge shop 2 floors lots of tools and lots of courage :) and plenty of $$$ I just like to not waste something that can possibly be salvaged and in my book the personal reward is a plus. Again keep sending any comments they are absolutely all welcome. One day I will post the before and after pictures.
 

Alumarine

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You haven't mentioned the drives.
Are they in good shape?
Are they mercruiser?
 

acadian2022

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Good morning all. the drive are OMC and look to be in good condition on the exterior zero scuff but will get to that once engine are ready. a Kudos to Bondo, I went to the machine shop with the 2 blocks and 4 heads and I the very knowledgeable team said we could take your money and do what you asked however the issue they all agreed too is what about the interior integrity of the walls pitting and they suggested what Bondo said dump and find 2 truck chev blocks and go from there vs one that was in salt water. they assured me that once I move in that direction a complete review of the blocks would be done by the team at the shop. now I have to ensure I get blocks within the same year so all the accessories would fit including mechanical fuel pump unless I want to have more modifications. For Scott suggestion I will also read up on his recommendation however one mention I then need the hardness since it is control by computer?

To all it blows my mind to have folks from all over read post and help someone they don't even know and that is absolutely amazing you are all GREAT People that's for sure! Thank you thank you thank you.....
 

Scott Danforth

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For Scott suggestion I will also read up on his recommendation however one mention I then need the hardness since it is control by computer?
only if you convert to fuel injection. the block and heads dont have a clue if its a carb or EFI up stream.

the vortec cylinder heads just require a different intake than the earlier SBC's since you have to buy two new intakes anyway as yours were in salt and most likely rusted beyond use.
 

acadian2022

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only if you convert to fuel injection. the block and heads dont have a clue if its a carb or EFI up stream.

the vortec cylinder heads just require a different intake than the earlier SBC's since you have to buy two new intakes anyway as yours were in salt and most likely rusted beyond use.
Ok thank you Scott, I will show my friend your suggestion since he is way more knowledgeable then I, I figured the more I keep things the same would ensure the rest of the parts will fit well, should one be concern about the stern drives if you increase the HP of an engine I would imagine the stern drive should match the performance of the engines?
 

acadian2022

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Ok thank you Scott, I will show my friend your suggestion since he is way more knowledgeable then I, I figured the more I keep things the same would ensure the rest of the parts will fit well, should one be concern about the stern drives if you increase the HP of an engine I would imagine the stern drive should match the performance of the engines?
Oh Scott, could you provide me with example vortec block and a intake that would work well for my project, as mentioned for me HP is by far my goal as long as I keep it within the HP of the boat design to a degree that is. from my reading some Bayliner 2850 came with 305 / 350 and apparently Volvo engine all as optional when folks was ordering that boat.
 

Scott Danforth

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Oh Scott, could you provide me with example vortec block and a intake that would work well for my project,
are you running a heat exchanger, or just raw water cooling. if raw water, do you want cast iron? or dual alloy aluminum? 2-barrel or 4-barrel?

there is no HP limit on boats with I/O's, only on boats with outboards
 

acadian2022

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are you running a heat exchanger, or just raw water cooling. if raw water, do you want cast iron? or dual alloy aluminum? 2-barrel or 4-barrel?

there is no HP limit on boats with I/O's, only on boats with outboards
Im seriously considering heat exchanger close loop vs what was in prior open loop salt water. the set up was two 305 - 4 barrel I was reading best to stick with cast just in case I don't add a heat exchanger
 

acadian2022

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Im seriously considering heat exchanger close loop vs what was in prior open loop salt water. the set up was two 305 - 4 barrel I was reading best to stick with cast just in case I don't add a heat exchanger
are you also saying that my flywheel ring gear will also be a perfect match bolt pattern etc, what about existing motor mount assuming modification in the engine compartment would be required?
 

Scott Danforth

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Im seriously considering heat exchanger close loop vs what was in prior open loop salt water. the set up was two 305 - 4 barrel I was reading best to stick with cast just in case I don't add a heat exchanger
I would stick with aluminum. Edelbrock 2519 is the dual alloy (bronze water passages) like the OEM Volvo/Ilmor intakes.

are you also saying that my flywheel ring gear will also be a perfect match bolt pattern etc, what about existing motor mount assuming modification in the engine compartment would be required?
flywheel is same for 305/350 after 1986
 

acadian2022

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I would stick with aluminum. Edelbrock 2519 is the dual alloy (bronze water passages) like the OEM Volvo/Ilmor intakes.


flywheel is same for 305/350 after 1986
Yes but would example my existing bellhousing and flywheel ring gear fit a Vortex engine?
 

Scott Danforth

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Yes but would example my existing bellhousing and flywheel ring gear fit a Vortex engine?
and even the later LS and LT motors. the GM chevy bolt pattern will also bolt up Big Blocks, in-line 4's and 6's, etc.
 
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