Logo
FULL SITE MENU

Old School 68-78 issues/questions

A

ARCTICMUTT

New member
I recently acquired my first boat and it came with an old 4 cyl 50 hp merc and an 85 hp merc both jets. The guy I got it from said the 85 had lost spark last year and they had traced it to a part, pulled that part to find a replacement and then lost the part. The part is electronic and is bolted to the backside of the plate at the bow side of the engine. Sounds simple right? According to the serial number on the engine it doesn't exist...3186734. The 50hp 2307952 is supposed to run good....haven't tried starting it but it has good compression and spark so feel confident. In my naivety I jumped on craigslist and found another 85hp merc from the same area that had lost compression on the top cylinder and bought it 4720010 (77) thinking that all mercury thunderbolt ignitions were the same.... So now I have 2 non running 85hp engines. I have found 2 more of the 77's 85hp in my area both in unknown condition except one has strong compression.
Question 1:

Do I try and round up the parts for the original 85 or get the other 2 77's and try to make them work?
note: I live in Alaska and like to have spare parts if available because where I'll be going is sometimes hundreds of miles from civilization.

Question 2:

I have found a spare 1973 50hp engine and was wondering if any parts would cross to either of my original engines?

Question 3:

Is there anyway to bypass the part that is missing?

Thanks in Advance
 
The part you need for the 85 is called the switch box. Lots of them on sale on E-Bay for under $100.

Moore power is usually better, so I'd fix the 85.

Jeff
 
Thanks for the name on that, is there year/hp range that crosses? I am planning on running an 85 I was just wondering if the cdi over the distributor is better?
 
You can run one or the other, depending on the motor. The distributor motors are very different from the ADI (all electronic) engines. So far, all of the switch boxes for 3 and 6 cylinder ADI Mercs I've used interchange.

Jeff
 
Back
Top