Help with replacing merc 305 with a merc 350

[mberliner1626]

I have a 1984 Grady Offshore with a merc 305 w/ alpha one.

I've located a running merc 350 (stock) from a donor boat. The casting ID is 14093638 - it's a 1987, 1 piece rear mail seal.

Will this be a direct drop in? without any changes/mods?

If this is a direct drop in. I'm going to hear it, see it run and conduct a compression test on the motor, prior to purchase. Is there anything else I should look for?

Thanks now for the help and any info...

 

[Fishermark]

Re: Help with replacing merc 305 with a merc 350

If I am not mistaken, your original engine will have the two piece rear main - you will need to swap to a new style of coupler at the least. But the swap should be fairly straight forward and not too difficult.

 

[Flysfloatsor]

Re: Help with replacing merc 305 with a merc 350

Yep, coupler. you should get a new one anyway. because failure means pulling the engine.
Id try hard not to touch the 350 distributer, wires... etc. if it was running good in the other boat.

 

[Bondo]

Re: Help with replacing merc 305 with a merc 350

If I am not mistaken, your original engine will have the two piece rear main - you will need to swap to a new style of coupler at the least. But the swap should be fairly straight forward and not too difficult.

Yep, coupler. you should get a new one anyway. because failure means pulling the engine.

Ayuh,... Welcome Aboard,... 'n Sierra makes a conversion coupler, Just for that application,....

18-2172,.... I believe iboats carries 'em, 'n I know Napa can order it...

 

[84EdH]

Re: Help with replacing merc 305 with a merc 350

this is a link to what they call a conversion coupler. http://www.iboats.com/Engine-Couple...8753477--session_id.417136823--view_id.172601

You will need a different flywheel also. the bolt pattern on that old engine is different than the new one. you need a flywheel that is the same diameter as yours, has the new bolt pattern, and works (teeth wise) with your starter. if I see a link to that flywheel part number I will post. good luck!

 

[84EdH]

Re: Help with replacing merc 305 with a merc 350

this is a Barr flywheel designed to convert the old 2pc rear seal to 1pc. it is a 12 3/4" that should be what you need. I think the flywheel on the 87 engine will be 14" Barr 24-14088650

 

[Reel Poor]

Re: Help with replacing merc 305 with a merc 350

Ayuh,... Welcome Aboard,... 'n Sierra makes a conversion coupler, Just for that application,....

18-2172,.... I believe iboats carries 'em, 'n I know Napa can order it...

Since these are both Alpha One assemblies why does he need a conversion coupler if he has a complete donor assembly, bell housing, coupler, flywheel, and starter? He didn't say it was that complete but, for the sake of knowledge let's say it is.
Is there a difference in the intermediate transom plate that requires him to use his original bell housing?

 

[FreeBeeTony]

Re: Help with replacing merc 305 with a merc 350

Just curious............

What are your numbers w/ the 305?

What prop are you turning?
WOT?
Cruise at 3600RPM?

Just looking for a comparison............

 

[Bondo]

Re: Help with replacing merc 305 with a merc 350

Since these are both Alpha One assemblies why does he need a conversion coupler if he has a complete donor assembly, bell housing, coupler, flywheel, and starter? He didn't say it was that complete but, for the sake of knowledge let's say it is.
Is there a difference in the intermediate transom plate that requires him to use his original bell housing?

Donno RP,... That's 1 of them "Gotchas" I've run across...

Flywheel covers, 'n inner transom plates, Should interchange,................ or not....

If fully dressed, no doubt he should have parts enough to Make it fit....

 

[Reel Poor]

Re: Help with replacing merc 305 with a merc 350

Donno RP,... That's 1 of them "Gotchas" I've run across...

Flywheel covers, 'n inner transom plates, Should interchange,................ or not....

I just did some part comparisons and from what I found I believe if it's a "complete" donor, it "should be" a simple package exchange.
If this was a long block exchange or being installed in front of an R or MR drive the scenario changes completely.

 

[mberliner1626]

Re: Help with replacing merc 305 with a merc 350

Sorry I can't help.

I've never had this boat in the water... picked up on the super cheap as is. I'm trying to get it wet again.

I believe this project is going to expand, so I will start taking photos and the such to keep track of it.

Edit - this was in response to FreeBeeTony - sorry about any confusion. I'm new to this whole posting deal also.

 

[mberliner1626]

Re: Help with replacing merc 305 with a merc 350

I've pulled the 305 out, went fairly easy. Only had to grind the head off of one mount bolt.

Now, I've found a running, freshwater, good compression, donor 1989 5.7 merc complete with the drive (Alpha 1) and all associated pieces, parts and goods. Now I should be able to replace everything and have no major issues... right?

Everything in the bilge looks to be ok... except where the motor sits. I don't know the name of this, but it looks like a box, fiberglassed over and attached to the stringers? It looks like it may have split on one side.

Also the stringers don't run all the way to the transom? Could this be right? Looks original to me?

I'll be posting pictures after the bilge is cleaned out and asking for help and info!

Thanks guys!

 

[mberliner1626]

Re: Help with replacing merc 305 with a merc 350

Attached are some photos of what I have found. There needs to be some cleaning done, but you can see the split in the motor mounts. Not so sure how to handle this yet. I'm going to clean up everything so I can get a better look at it.

Also look, the stringers don't go all the way to the transom? It looks original? Does this make sense? Should I leave it as is? Or cut it back, clean it up and run them up the transom?

I also pulled up the rear fuel cover and found... NO TANK! Didn't expect this! I did pull the cover on the front tank and it is there. Anyone have any idea how I can get a 1984 Grady offshore tank made up, without an old tank as a template? I'm in North New Jersey, I remember reading about a company in Long Island that fabricated tanks, but with a template. Eh! Hope this won't be a PITA!

Except for some slime, dirt and grit the compartment seems to be in good shape, solid all around (a good cleaning will show the truth). Except for the wall between the rear fuel tank compartment and the bilge... rotted wood. My question is should I cut out entire wall and replace? Or cut out the rotted ply and keepthe fiberglass and fill it?


Here are the split motor mounts, in the corner of the blocks.








Here is where the stringers don't touch the transom.

 

[mberliner1626]

Re: Help with replacing merc 305 with a merc 350

Here are some photos of the rear gas tank compartment and rotted divider.











Any advice, ideas, etc is appreciated.

 

[Bondo]

Re: Help with replacing merc 305 with a merc 350

Any advice, ideas, etc is appreciated.

Ayuh,.... Take yer hull/ stringer problems over to the restoration forum, 'n start a thread in there....

Bring this thread back up, when yer ready for more motor work...