120HP ob - measurement for splashwell size

[ctswf]

I'm about to shorten the depth of a splashwell on an 18' starcraft.
Max hp on this boat is 120HP.

About how much clearance do I need when the motor is up, measuring from the face of the transom going forward?

My 70hp only needs about 18" of clearance, of course I would like most motors within the 120hp rating to fit.

thanks

 

[Texasmark]

Re: 120HP ob - measurement for splashwell size

It's more than just the engine. The 70 and 120 probably tilt up at the same angle and have roughly the same forward overhang. Reason being is that the crankshaft has to be in a certain position to match up with the required dimensions of the lower unit and in front of that is the intake manifold, the carbs, the airbox, and the cowling which are pretty much the same dimensions.

What you have to allow for is the shifter and throttle cable routing which has to come out from the engine and make an arc of at least 12", preferably more like 18" to prevent kinking the inner cable. This measurement has to be made not only with the engine in the operate position but also in the tilted up position.

You should have the same problem with your 70 so I'm going to stick my neck out (not very far) and say if your 70 fits a 120 will fit.

Mark

 

[GA_Boater]

Re: 120HP ob - measurement for splashwell size

Measure from the top of transom to the top of the cowling. That's your distance and it leaves enough clearance for the top of the cowl in trailer. And the splashwell has plenty of room to accommodate the cables. I know what TM is talking about, but it doesn't apply. Why - You won't be operating the controls when the motor is up in the trailer position so no kinking, just bending like they are designed to do.. His crankshaft talk left me in the dust.

 

[roscoe]

Re: 120HP ob - measurement for splashwell size

What 18' Starcraft are we talking about?

And what brand of 120 hp motor?

I had an 18' SS, and the splash well was about 34" front to back.
My 18' Mariner has a similar angle to it, but is about 26" front to back, as the gunnel height is lower on the Mariner.


As for the motors, I believe an OMC v4 120 will not be as tall and therefore not hit the front of the splash well as easily as my Merc 115 inline 6 cylinder.

Below is a photo of my Merc I6 115, fully tilted.
I could only move the splash well back about 1.5" before it would hit the front of the engine.






The splash well on the 18 SS is huge, deep and long.
The 21'ers are even bigger.

When I find my 21 Mariner, the splash well will be shortened, and probably lowered on the bow end, as that is all that will be needed on the waters I boat on.

 

[Texasmark]

Re: 120HP ob - measurement for splashwell size

His crankshaft talk left me in the dust.

I was just thinking about things that would make the dimensions similar. The crankshaft has to go through to the lower unit in the same place and the mid section is about the same distance from the transom. To me that establishes the location of the block to the transom bracket. The rest is just ad ons.

On the cables, moving and twisting or not, there is a limit as to how much they will twist and bend before kinking. Having had a kinked steering arm cable, that someone else kinked, I don't like kinked cables.

Mark

 

[ctswf]

Re: 120HP ob - measurement for splashwell size

18' 1969 offshore v, massive 36" splash well. In this picture you can see what I was planing on doing. When tilted up, any motor would be in front of a "wall" and never be hanging over the splashwell like in Roscoe's picture.

Im going to use my 1982 70 evinrude, plenty of space. No other motors in mind but I want to leave enough space for future upgrades...what that would be I do not know.

Roscoe, whats the merc 115 measure from the front of the transom to cowling? I doubt I would find any motor any taller than that.

thanks

 

[GA_Boater]

Re: 120HP ob - measurement for splashwell size

A Merc Tower of Power is about the tallest motor out there. That is a good reference to use in case you re-power later on.

 

[glenn property of pam]

Re: 120HP ob - measurement for splashwell size

if you are planning on staying with evenrude then the 120hp around 198* is terrible as it over hangs the back off the transom bracket as i found out when i traded my 70 for the 120 and ended up lifting the motor and adding a jack plate so it could be tilted

 

[ctswf]

Re: 120HP ob - measurement for splashwell size

I dont really understand what you mean glenn (i'm not all that familiar with different motors, I've only owned one for the past 7 years of my boating)

 

[glenn property of pam]

Re: 120HP ob - measurement for splashwell size

I dont really understand what you mean glenn (i'm not all that familiar with different motors, I've only owned one for the past 7 years of my boating)

This is a old pic of my 120 mounted and you can see the distance between the 2 lines

 

[GA_Boater]

Re: 120HP ob - measurement for splashwell size

Glenns motor has a lot of overhang above the tilt tube compared to others. When the motor is raised all the way, more of the overhang rotates into the splashwell. I think that's what he is showing.

 

[ctswf]

Re: 120HP ob - measurement for splashwell size

Ah i see what u mean thanks for the heads up. I still havn't made the move ill post some pics when I do

 

[roscoe]

Re: 120HP ob - measurement for splashwell size

Tilt tube is 2" above transom. And 1/2 inch in front of transom.

From the top of the transom, to the top of the motor, 29".

 

[ctswf]

Re: 120HP ob - measurement for splashwell size

From the top of the transom, to the top of the motor, 29".

Holy sheeet! my friends 150 Johnson only measure about 22"

[edit] actually what I said isn't exactly correct, I believe 22" was from the transom measuring horizontally level, to where it would hit, as the splashwell is going to pretty much be a straight wall in front of the motor.

thanks for the info, even knowing this I think im going to still shrink it to a point where the tower of power would not fit.