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Mac
11-01-2005, 10:20 PM
Does anyone know if you can get a jig for the engine mount layout for a Mercruiser 300hp Horizon 5.7l? I assume it just uses the two mounts on the transom assembly and then two conventional engine mounts. I am planning on putting one in a boat that had a engine with a front engine mount so there are no mounts for a V8, I need to mock up a cradle for the engine mounts between two stringers and a jig would be a lot easier to work with than the engine itself. Thanks.

MOP
11-01-2005, 10:33 PM
As far as I know there is no set up jig, what OEM's use is a transom fixture at a standard X dimension and set the mounts on the stringers. The stringer hiegth is determined by the type of mount you chose, the later Donzi's mount on about a 7 inch stringer with the mounts sitting on angle iron that is bolted over the top of the stringer. The older models had higher stringers with the angle iron bolted to teh inside I beleive the stringers were also set further apart.
What engine in what boat, I will try to get you straight on mounting it correctly but need the particulars.

Phil

Mac
11-01-2005, 10:53 PM
The boat had a 3.7L 180hp motor in it with a alpha, the motor has a bracket on the front that bolts to the floor in front of the motor to support it, that and the transom assembly are the only two mounting points. The boat has two stringers about 40" apart, I planned on making a cradle from steel that would go between them basically clamping over them, and then mount the engine mounts to that, the cradle would have to dip down the the middle to clear the oil pan. The boat is a 24' Bertram, I had the idea of doing it this way after looking at how the engines are mounted in a Sutphen.

MOP
11-02-2005, 12:13 AM
Typical mounts are 22" on center. If you have the ability to hang the engine it will make life easier, put the rear mount bolts in get a basic alignment with the Merc tool. With the engine hanging it is fairly easy if you have the tools and welding equipment. I can walk you through a standard I/O in my sleep, I can do this but it is one of those I need to be there!! If you want to chat about it drop me a PM with your number.

Phil

Mac
11-02-2005, 06:32 AM
This is what I am thinking, I guess I will just use the engine and the alignment tool, there should be enough adjustability in the mounts to fine tune it once it is in, the is the strongest mount style I could think of without having to build new stringers.

MOP
11-02-2005, 08:11 AM
Looks like you are on track should work out just fine, having the engine in place and closely aligned will help. Another plus is to bolt the mounts on the engine set at about the 1/2 way adjustment point. I don't like tubing some do me I would recommend due to the span using 3-1/2" X 3-1/2" 3/8" angle iron flat side down that will compress the weld rather then pull on it, if you go flat up to be on the safe side grind the weld flush and fish plate over it. A little over kill never hurts. Post some shots of your progess!

Phil