318 swap turned to a 360 swap need advice

"Well I sent a buddy of mine t

"Well I sent a buddy of mine to pick up an engine to replace my dead 318 while i was out of town and it turns out it wasnt a 318. Much to my surprise when I checked the plate it is a 360.

So what i have is a 1981 (supposedly) 360 that is going in place of a 1973 318. I have both engines complete with transmissions.

The original engine specs are as follows

model lm318bwr10/380
serial E193883

replacement

model mm360bwl19-718
serial e-593418

My boat has a 1" shaft if my memory serves, I am not sure if that matters

Now what I understand from the model numbers is that the transmissions have different ratios and that the 360 is the opposite rotation of the 318. Both Transmissions are velvet drives.

What problems am I most likely to run into with this swap, I am an outboard mechanic, but have limited experience with inboards and chryslers. Namely my only experience is with this specific boat which I have had for a little over a year.

Also any suggestions on resources for wiring information, the harness in my boat is most likely different than this one. I have ordered a service manual from this site but I am not sure how indepth it will be and I am in a time crunch to get his put together before the boat season hits in full and i dont have time for major work on my own boat.

Thanks for the help in advance."

"The replacement is a standard

"The replacement is a standard Left or counter-rotating engine with a Borg Warner transmission with a reduction ratio of 1.9 to 1.
The only issue I can think of is the prop and shaft diameters. The 360 with a reduction trans will put out more torque than the 318. Your original trans was a 1:1 so the shaft was probably only 1" and the prop was probably a smaller diameter and less pitch than you will want using the 1.9:1 reduction trans. According to my manual, that trans will turn the prop in the opposite direction from the engine, so even though your new engine turns left, the prop will turn right as it did with your 1:1 trans."

"Well that is good information

"Well that is good information, You are correct about the shaft however. So does this mean I need to upgrade shafts?"

"If you use the 1.9:1 trans yo

"If you use the 1.9:1 trans you probably would have to upgrade your prop shaft. The shaft will be shorter because the 1.9:1 trans is longer than the 1:1 trans. The good news is that there are newer (more expensive) stainless aloys that are stronger so you can use a new 1" shaft and keep your old cutlass, bearing, shaft log, etc. You won't want to use the old prop because the new 1.9:1 trans will be turning it at almost half the rpms compared to your 1:1 trans.
I would first determine the maximum diameter prop that I could use given the angle of the shaft, distance from the rudder and hull clearance. Then I would figure out how much pitch and cup I needed. You might want to go to a 4 blade prop.

Another simpler option is to reuse the old 1:1 trans with the 360. To adapt the 1:1 to the 360, just unbolt the 4 bolts holding the pump onto front of the trans and rotate until the arrow matches the rotation of the 360, then tighten the 4 bolts. You will need a new prop because the 1:1 trans does not change the direction of the engine rotation.
"

Michael:

Do NOT try to use

Michael:

Do NOT try to use that 1.9:1 reduction trans! You'll never get a prop that will work with it. Per my calculations (hah!) you'd need a prop that was at least 19 to 20 inch diameter. See what I mean.

Jeff

"Let me provide an example to

"Let me provide an example to further Jeff and Peters notes. I am running a 29 ft semi displacement hull with a lm 318 cw rotation coupled to a BW 1.91/1 gear, turning a 1 3/8"SS aquamet shaft and a 17/18 ccw four bladed prop.
This results in:
Cruise RPM of 28-3200 at 16 knots
Max RPM 4200 at 20 knots.
Bottom line if it is a planning hull you cannot use the reduction gear with out some maajor mods."

"Hull is a 73 25' Trojan,

"Hull is a 73 25' Trojan, Its not a problem at this point to swap the 1/1 Transmission onto the 360 and put a different prop on, I have 3 that would work with that setup sitting here from the guy that does my prop repair. So at this point, can I actually put the 360 in with the 1/1 transmission from my 318, and use the current shaft I have with a propeller setup for the reverse rotation?"

"Yes.
It should bolt right on

"Yes.
It should bolt right onto the 360, which is a bored and stroked version of the 318 but with a couple different front-end components that do not affect the trans. The bell housings should be the same."

Don't forget to rotate the

Don't forget to rotate the pump body on the 1:1 first so that the arrow on top matches the rotation of the engine. If you don't the trans won't work.

"I would take Jeff's advic

"I would take Jeff's advice. He's always right.
But if you don't, here's a prop that you might consider:
"

..."He's always right.

..."He's always right."

Yeah; and my wife agrees with you!

Use the 1:1 drive and you'll be on your way.

Jeff

Wow that is one heck of a prop

Wow that is one heck of a prop! Hmmmmm wonder if the boat would float with that attached.......

I just want to say thanks a million for the great advice. We are going to start swapping out the trans next week hopefully and just maybe get the old girl put back in the water soon.