Confusion on a 1976/1986 Mercury 115 Hybrid

[frozenokie]

First - Here's the Mercury I have. A 1976 shell (Lower unit, mid-section, motor mounts, tilt/trim, cowlings) and a fresh rebuilt 1986 power head, electronics, and carbs.

What's needed - I have to replace the upper motor mounts on this motor since they are shot. After talking with a certified Mercury mechanic, he told me when I was trying to order the two correct base gaskets, that the 1986 model 115 cannot and will not mount to the 1976 mid section. He says the only head without a distributor that will mount to the 76 base is a 150HP power head and, in other words, any of the 115 power heads that are electronic ignition will not mount to the 1976 base. He assured me that I have a 150HP head on this motor.

Does this ring true to anyone? I have already ordered the gaskets and I hope they fit.

Is there any distinguishable signs, model or serialo numbers stamped on the power head that I can use to identify what head is on here? If so, where do I look for them?

I do have a shop manual that I looked in for answers. The only thing I could find is that the firing order is different between the two motors and I'm pretty sure that the firing order that shows on the head cover plate is 1-4-5-2-3-6, which matches that of the 1976 115... so I don't know what to believe now

Believe me when I say this is a pleasant surprise if it is correct in what he said. But, I want to be sure of what I have before I order any more parts in the future. Any Mercury gurus out there???

 

[Chris1956]

Re: Confusion on a 1976/1986 Mercury 115 Hybrid

I do not think all of his ramblings are true. For one thing, the '76 115 and 150 are the same block, except for the 150HP has more radical timing on the transfer ports, and perhaps the power port pistons. The powerheads will interchange. so if the '76 150 Merc midsection will mate with the '86 115HP, then the '76 115HP midesction should mate with the '86 115HP, as well.

The gaskets will tell you for sure. Can you get the exhaust extension off the '86 motor? That would likely cinch it. The midsection and the lower unit will likely work OK, as well. The wiring harness will hook up a bit differently. The white wire on the '76 motor harness is +12V DC to the battery powered switchbox. You do not have this feature on the '86, so tape it off. The orange wire on the motor harness is the killer wire for the '86 switchbox. You need to hook this up. BTW - Do you have a killer wire on that '76 motor harness? If not, you will need to get a new motor wiring harness or jury-rig something. The killer wire does exist in the boat's wiring harness of the '76.

You might drop a PM to Clams Canino if you have more questions.