Engine swap, 305 to 350

Skutt

Seaman Apprentice
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Apr 8, 2015
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31
I have time now to put a plan together for reinstall. I have the 305 striped down to the bare block so I will clean up the engine compartment in the boat and get that ready for install. I also have to clean and paint all the marine parts so they are ready to put on the 350. I would like it to be a nice clean setup when it's back in running condition. No sense putting the 350 in and leaving things looking like it does now after so many years of use.

I think it will go back in easily since it is pretty much a wide open engine compartment. I have to order the marine head gaskets and soft plugs. It looks like my best source for those will be Summit Racing.

As I drive around the area and see so many boats out on the water enjoying nice spring weather I am anxious to get this boat going so my wife and I can do the same.
 

Idlespeedonly

Senior Chief Petty Officer
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Jun 30, 2011
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Here is a link to the factory service manual. Is can also be found in the adults only sticky at the to of the OMC forum here.
 

Skutt

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Apr 8, 2015
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Thanks Idlespeedonly, downloaded it and got it saved. Will be real handy to have. I pulled the heads off the 305 a few minutes ago. The gaskets are completely rusted away around the water ports. The cylinder walls have a good ridge at the top so I am thinking it was just time for this engine to be replaced. I will pick up the marine head gaskets and soft plugs tomorrow for the 350, I think I have everything else I will need.
 

Skutt

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Apr 8, 2015
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I have the 350 nearly ready to put in the boat but I have another question for anyone that knows. I was comparing the intake manifolds and wondering which one to use. The only difference is that the 305 marine manifold has a vacuum diaphragm on what would be the passenger side of the manifold beside the carburetor. I isn't hooked to anything but the 350 manifold doesn't have a place for that diaphragm to be bolted to. Is the manifold off the 305 specifically for marine applications? If so I will use that one. The casting number is 14057055. It seems to be a stock manifold for either 305 or 350. I don't think it matters which manifold of the two I have that I use. The other one is casting number 3973468.
 
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Bondo

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The only difference is that the 305 marine manifold has a vacuum diaphragm on what would be the passenger side of the manifold beside the carburetor.

Ayuh,.... That sounds like an egr valve used on Cars,....

Boats don't use 'em,....
 

Skutt

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Apr 8, 2015
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I think your right Bondo. I noticed it when it was still in the boat and I was running the engine listening to the knock. It doesn't have anything connected to it so doesn't need to be there. Looks to me as though the 305 was not the original engine although the boat has the 5.0 Liter sticker on it. I just want to make sure I do it right since it is my first experience with an inboard engine. I have the boat ready for the engine again and might install it this next weekend. I ordered an oil pump priming tool today and want to run the oil pump while the engine is on the stand to be certain it is getting well oiled.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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As I stated prior, pretty sure your 305 is a junkyard motor. the EGR confirms that. Now that you are buttoning up the long block. check out the starter, alternator and distributor. if you do not see SAE J1171 on them, then they may also be automotive and not marine.
 

Skutt

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Apr 8, 2015
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The distributor and alternator are marine for sure. I didn't think about checking the starter but I will do that, thanks for the input. I have an HEI distributor I am thinking about using but I am not certain those are ok for marine applications. It doesn't have a vacuum advance so I think it should be good to use.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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I have an HEI distributor I am thinking about using but I am not certain those are ok for marine applications. It doesn't have a vacuum advance so I think it should be good to use.

if and only if it is a DUI Marine unit (HEI clone that has been tested and certified to SAE-J1171)

if it is not J1171 compliant.........BOOM!
 

Skutt

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Apr 8, 2015
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Thanks for the heads up on J1171 compliant components Scott. The distributor that was on the boat has that tag but I didn't see that tag on either the starter or alternator. I need to clean them up to be certain I am not missing it though. Getting ready to go to work this morning will find time to do that later.

The boat is old but worth doing things right. Besides, done right is safe and done cheap isn't. I just watched a youtube video about marine components and the differences from auto components. I think the alternator that was on the boat is marine compliant because it has the screen spark arrestor on the back. I will make sure all parts are correct before it goes out on the water.
 
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Skutt

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Apr 8, 2015
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I have determined that all the engine components are in fact marine parts. Alternator, carb, starter, ignition. I will be going back out to the garage this morning and finish getting the engine ready to install, might even have it in the boat today.
 
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