135 hp tower of power swap

[ottsixx]

I bought a fishing boat with a 1978 mercury 1500 {150 hp} and the powerhead is blown and Ive found someone with a new or newly rebuilt 135 hp inline 6 mercury and Im wondering if the 135 hp engine is a drop in replacement for the blown 150 hp and will it be easier to swap the carbs out and rejet or find the propper carbs or is there anything I should know or be aware of and thanks in advance for any advice given on the matter...................

 

[jimmbo]

Re: 135 hp tower of power swap

First of all the 1978 150hp was a V6. The Inline 6 150 (1973 - 1977 ) were not the same block as the 1970 - 1971 135hp and had different bolt pattern to the midsection.

 

[emckelvy]

Re: 135 hp tower of power swap

The 135hp powerhead will not fit a '72 or newer tower. '72 and newer use a different design of tuner plate (a 2-piece, thicker plate) which is not compatible with the older, open-plenum 1350 block. If you had a 1350 (or '70-'71 1150) mid-section, it'd bolt right up in place of your 1500 mid and you could bolt up the 1500 lower unit as well.

The 1500 carbs should be compatible, maybe re-jet them to .080 but you'd be pretty close in any case, running ethanol-fuels she'll run leaner than in the Old Days with good gas!

The 1350 is a non-power-ported-piston motor with very large intake/exhaust ports, it's a strong runner and no other inline except a power-ported motor will touch it. The other concern would be the ign systems, if your 1500 is distributor-fired there's no problems, all will swap over just fine. If the 1500 is an ADI, that's not compatible with the older distributor motor, without a ton of mods.

BTW the 1350 crankshaft would interchange with the 1500, however you'd need the correct pistons for the application (unless they used 'holey' pistons in the 1350 when it was rebuilt).

HTH & G'luck.........ed

 

[ottsixx]

Re: 135 hp tower of power swap

the 1500 might be a 1977 but it was sittin on a 1978 cajun boat and I guessed prolly the original engine on the boat but it is surely the inline 6 tower of power engine and the engines sure look an awful lot alike to my memory.

 

[Chris1956]

Re: 135 hp tower of power swap

Ed, there were no Merc 1500s with ADI. There may have been a late '79/'80 Merc 1400 with ADI.

Ott, I would think the 1350 would bolt right up as a total replacement for the 1500. Check the electrics, although I would think they would fit as well.