old 3.7L engine...swap out for 4.3,3.0 ?????

[courteousmick]

hello. i have this nice 1986 21' cobia with an old merc 3.7L L4. the engine is trash - salt water and age killed it. can i install a 3.0, 4.3 or any other known, more popular engine size? i would hate to let this beauty rot away just because of its engine. thanks in advance.

 

[courteousmick]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

i am an auto repair shop owner so any type of engine replacement possible if i'm going in the right direction. thanks again

 

[achris]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

Mick,<br /><br />Welcome to iBoats.<br /><br />If it were me, I'd be thinking more along the lines of a 305 Chev. <br /><br />You've got the right size boat for it. There's plenty of them around and parts are really easy to get. Find a dead one (for the flywheel housing and mounts and exhaust system ect) and go from there. You have an auto repair business so it should be a dead easy one for you. Just be aware that the gear ratio in the leg is slightly different (3.7L has 1.84:1, 2 bbl V8 wants 1.65:1, 4bbl V8 wants 1.5:1) so you would end up running a higher pitch prop, and the yoke is a different length.<br /><br />Chris...........

 

[courteousmick]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

thanks for the info chris. a 305 if available right now but i was more worried about fitment. if anything will fit with a little modification then i can do it. thanks again.

 

[Bondo]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

If you modify the engine bay to accept the 4.3l, <br />You can reuse the outdrive you have now(same ratio is used).............<br />Going to the 3.0l will require a 1.98/1 ratio.......<br />A V-8 will use a 1.50/1......<br />(Why even consider a 305, 350 is the same block, for the same money,....FREE HorsePower)<br /><br />It's an Easy Swap...........<br />Go For It.........................<br />

 

[achris]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

Free horsepower = more speed.<br />More speed = "Why am I flying?" <br /><br />Chris..........

 

[courteousmick]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

great guys thanks for the ideas

 

[Donaldeh]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

Sounds familiar, maybe you guys can help me.<br />I have a 1984 Four Winns 20.5 ft with a blown up Mercruiser 470.<br />I don't really want to get into the gas usage of an 8 cyl. Would you know what 6 cyl replacements would "bolt right on" to my drive, without much modification needed in the engine compartment? Might there be an automotive engine that I could get from a scrapyard that might work, and what modifications would I have to make to it?<br />Thanks<br />Don

 

[Bondo]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

Same Exact Answer as Above.........<br /><br />The 4.3l V-6 Mercruiser...... <br />Chevy......<br />Truck motors work with only a little modification........<br />

You've got the right size boat for it. There's plenty of them around and parts are really easy to get. Find a dead one (for the flywheel housing and mounts and exhaust system ect) and go from there.

Frozen Donor Motors are what I look for.........

 

[Donaldeh]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

Thank you very much

 

[Bob_VT]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

I would carefully examine the mounting of all the motors. The 470 has a front mount. If you stay with a 470 you will not have to change mounts or outdrive.<br /><br />The 4.3 does pack more HP but really not that much more. You will pick up more weight and have to change your harness too. The 470 is a good motor and to get back on the water fastest and easy... just replace the 470.<br /><br />You will end up with more $$$$ in your pocket too.<br /><br />Bob

 

[Airpacker]

Re: old 3.7L engine...swap out for 4.3,3.0 ?????

The golden rule is "Anything can be done, how much money do you want to spend"? The conversion will require a lot to be changed. If you can do all the work yourself and scrounge lots of used parts( motor mounts, manifolds, Y pipe, bell housing, coupler,flywheel,wiring harness etc as well as all the necessary dressing components for a 4.3( raw water pump and all the brackets for alt,power steering pump etc) it can be done fairly economically. If you have to go to pocket to have it done, its gonna cost you a pant load of bucks