ENGINE SWAP 305 merc to 350 chev truck

[DAN0]

Hi,<br /> Just discovered that my 305 mercruiser is spent. I have a 350 chev 3/4 ton truck engine in my garage. Will this work in my boat. I know I will have to replace the gaskets and frost plugs. The 350 is currently in pieces. Is there anything else special I should do or replace while putting it back together so that it will work better in my boat? <br />

 

[TwoBallScrewBall]

Re: ENGINE SWAP 305 merc to 350 chev truck

Should work well. Starter, carb, water pump and distributor should be taken from the old marine engine, or bought new.

 

[KaGee]

Re: ENGINE SWAP 305 merc to 350 chev truck

You need a "marine" Cam also.

 

[TwoBallScrewBall]

Re: ENGINE SWAP 305 merc to 350 chev truck

A truck grind is close if not identical to a marine grind. Will work just fine.

 

[Bondo]

Re: ENGINE SWAP 305 merc to 350 chev truck

Ayah..........<br />Bolt it in,+ Go...........<br /><br />Course, You Could drop in a Big Crankshaft,+ a .030 overbore, <br />And, Build a 383....................

 

[jimmbo]

Re: ENGINE SWAP 305 merc to 350 chev truck

Don't forget to replace the core(freeze) plugs with brass ones too. As for the 'truck cam' chances are better than 99% that is GM 3896929 standard in most chev engines from 307 up to and including the 327/300hp and 350/300hp engines. Great automotive cam, not so good for a boat.

 

[Destin]

Re: ENGINE SWAP 305 merc to 350 chev truck

You need the marine fuel pump also. If its a late model 350 without a mechanical pump you will have mount a marine electric fuel pump, safety cutoff switch, and fabricate marine approved fuel lines from the pump to the carb.<br />Something similar to this engine, http://www.ebasicpower.com/images/BasePlus.jpg <br />to get an idea of how to do it.

 

[DAN0]

Re: ENGINE SWAP 305 merc to 350 chev truck

My 350 4-bolt came out of a 3/4 or 1-ton truck. Will I need another cam or not? Are the stock heads and springs good enough? The carb from my 305 is a two barrel. Will a 4-barrel from a truck work better?

 

[dcpcccrc]

Re: ENGINE SWAP 305 merc to 350 chev truck

be very careful doing this and dont use any parts other than the longblock from your truck. All marine parts are sealed so that no spark can be anywhere around the motor. in a boat the fumes stay in the engine compartment make sure you have a good blower. in a truck the fumes go right under the bottom and out the back so starters and everything for a car aren't sealed. a truck motor will work very well just not as long as a marine motor will. A automobile motor isn't made to be run at a constant 4800 rpms. After about 400 500 hours you could find yourself putting another block in it. where as a marine motor will last up to 2000 hours

 

[KaGee]

Re: ENGINE SWAP 305 merc to 350 chev truck

Originally posted by dcpcccrc:<br /> A automobile motor isn't made to be run at a constant 4800 rpms. After about 400 500 hours you could find yourself putting another block in it. where as a marine motor will last up to 2000 hours

Where did ya get that from??<br /><br />

 

[TwoBallScrewBall]

Re: ENGINE SWAP 305 merc to 350 chev truck

There is no difference in a marine block vs an auto block other than the stainless head gaskets and the brass freeze plugs. <br /><br />You will be better off with a 4 barrel, but don't use the one off the truck. It is vented differently than a marine carb. <br /><br />Cam and heads will work great.

 

[dcpcccrc]

Re: ENGINE SWAP 305 merc to 350 chev truck

thats funny i thought the cam, and valves, were different to, i could be wrong

 

[tommays]

Re: ENGINE SWAP 305 merc to 350 chev truck

i have never seen any motor that did not have real high end parts that will live long at 4800 car or boat<br /><br />the more rpm the more the parts cost or BIG BANG<br /><br />tommays

 

[DHPMARINE]

Re: ENGINE SWAP 305 merc to 350 chev truck

First thing I would check is the crankshaft flange,where the flywheel mounts.Most Mercs are internally balanced,meaning this flange is round.At least some auto V8's have external balanced cranks,and the flange has an offset balance area.The flywheel bolt patterns are different,and will cause you great difficulty.<br />DHP

 

[John Carpenter]

Re: ENGINE SWAP 305 merc to 350 chev truck

This is an easy conversion and will work fine as is IF the engines are both from the same year range. GM made some changes in the block in either 1985/86. If both engines were made either before (or after) this time then all of your sheet metal will interchange if need be, flywheel diameters & bolt patterns will be the same, drive adapters will interchange etc. Just use the 350 long block and bolt on all of the marine parts (starter, carb, fuel pump, alternator etc.) You should be fine.

 

[KaGee]

Re: ENGINE SWAP 305 merc to 350 chev truck

Originally posted by dcpcccrc:<br /> thats funny i thought the cam, and valves, were different to, i could be wrong

With a SBC engine, the block and heads are usually the same casting number, marine or auto. Valve train, pistons, rods, bearings all the same. In the majority of cases, the "marine" cam is different.<br /><br />However when it comes to me.... if anything can be different... IT WILL BE!!!!

 

[onespeed]

Re: ENGINE SWAP 305 merc to 350 chev truck

My marine mech. warned me about the alt. and starter "sparking" 2 weeks ago when I was contemplating taking the 2.5 out of my S-15 GMC to replace the 2.5 120 horse thats froze-up in my boat. *** He also warned***... if in the future you should sell the boat and you have left the truck/auto parts attached to the motor instead of marine type and forensics can prove it,,, and God forbid it sparks the fumes and KILLS someone, you MAY be held legally responsable.<br /> He also warned about changing the cam to a marine type,also the soft plugs, but that may only apply to my 2.5 scenario. I can't ad much more, but please do consider changing those things that go spark / poof in the bilge area, even if only for YOUR own safety! <br /> Cheers, Terry

 

[Bondo]

Re: ENGINE SWAP 305 merc to 350 chev truck

You would have Even Bigger Problems trying to swap-out your 2.5l.........<br />The motor you want to install is a Totally Different Casting...........<br />It Won't swap.... No How... No Way.....

 

[KaGee]

Re: ENGINE SWAP 305 merc to 350 chev truck

Originally posted by onespeed:<br /> My marine mech. warned me about the alt. and starter "sparking" ... Cheers, Terry

What? He didn't warn you about the spark plug wires too??? How incompetent! <br /><br /><br />(I'm soooo bad!.......snick)

 

[DHPMARINE]

Re: ENGINE SWAP 305 merc to 350 chev truck

KaGee<br />I've heard this also about plug wires (snick)<br />can you help me out on this?<br /><br />i need to get on the water<br />Doug