Mercury 15 HP race motor

[SS Minnow]

A 15 Force will walk a 15 OMC LOL both low hrs mid late 90s , proper tune , same boat.

Yeah, those Force motors were just known for settin the water on fire. Wonder why they went away???

[FMP]

Mostly dummies that didn't look after them with proper tuning.
It's true, I'm not the only one who has seen the Force.

[Spectre22]

the first couple pictures are the rough grinding from grinding out the edges. the rest of the pictures are of it case after i sand blasted it. im going to try to get some pictures of the exhaust work. but i just wanted to get these up first

[Spectre22]

what ive done on the exhaust side i still wanna even out some edges but its pretty much there.

[Spectre22]

Im also going to need a big carb for this motor so if anyone has a 20hp or 25hp please send me a PM!!!

[FMP]

Am I see things or does the bottom cylinder have a third downward facing port towards the tuner?

The view from the passage up , the right side semi circle corner. If you could use some high temp aluminum ceramic or weld fill it and grind smooth the curve. And the left side top edge, round the fall off nicely. With the cover on that last corner which forms on the bottom floor before the fall off towards the tuner. Does the cover have a shape to round that 90°. If it doesn't I'd try to make something work there so that S turn through to the tuner is more uniform and smooth.

[Spectre22]

No lol it’s the angle I took the picture. the port kinda wraps around cylinder so it looks like it goes downwards.

[Spectre22]

Also does anyone know where i can get props for this motor. ive seen cleaver looking props but can find any for a 15hp (8 spline)??

[Capt.Insane-o]

Powertec and solas

[Spectre22]

cleaned up the exhaust work a bit. evened out some of the edges and opened up the bend into the tuner a bit on the curves in the corners. this was only with the carbide burr, i still gotta sand and polish.

[Rmz_boi]

I’m just wondering what sort of results did you get? Rpm and power wise?

[25two.stroke]

Carbs from 6hp to 25 were IDENTICAL except for the bore size and the jetting. I would not go up to a 25 hp carb on that 15 right away. That is likely going to bog as that small displacmtent probably won't make enough vacuum even with the mods you did. I would get an early 18hp carb for one and change the linkage to work from the early to the later. Then get the jetting for that figured out and make sure the motor can pull fuel right. If you have any questions feel free to pm me or call me, I did that stuff a lot a while ago.

The exhaust pipe isn't tuned on those motors either, so some modifications there can yield quite a bit.

[Rmz_boi]

Carbs from 6hp to 25 were IDENTICAL except for the bore size and the jetting. I would not go up to a 25 hp carb on that 15 right away. That is likely going to bog as that small displacmtent probably won't make enough vacuum even with the mods you did. I would get an early 18hp carb for one and change the linkage to work from the early to the later. Then get the jetting for that figured out and make sure the motor can pull fuel right. If you have any questions feel free to pm me or call me, I did that stuff a lot a while ago.

The exhaust pipe isn't tuned on those motors either, so some modifications there can yield quite a bit.

Youll be suprised, I’m currently running a 34pwk on my merc 15 (same model as his) and I’ve had it running pretty well, it needs a lot of tuning still but once I have ported it it will run even better. Do you have any information on porting these motors?

[redbeard_1911]

Carbs from 6hp to 25 were IDENTICAL except for the bore size and the jetting. I would not go up to a 25 hp carb on that 15 right away. That is likely going to bog as that small displacmtent probably won't make enough vacuum even with the mods you did. I would get an early 18hp carb for one and change the linkage to work from the early to the later. Then get the jetting for that figured out and make sure the motor can pull fuel right. If you have any questions feel free to pm me or call me, I did that stuff a lot a while ago.

The exhaust pipe isn't tuned on those motors either, so some modifications there can yield quite a bit.

what would be the best mod to the exhaust pipe to get the most power out of it? we've got a river that's 10hp limit. i'm building a sleeper 9.9 merc. got everything to make it a 15, but i'm gonna try and squeeze all i can out of it.

[rossi]

Buy a OMC 15 LOL

True - I have both an 87 Merc 15 and an 87 Evinrude 15 that I use on a 14' Mirrocraft Deep Fisherman and the OMC is not only faster but has more torque. The Merc even has quite a bit less hrs to boot.