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Message |
    
Steven S. Burris
Member
Username: shaneburris74
Post Number: 8
Registered: 03-2008
| | Posted on Wednesday, March 26, 2008 - 09:37 pm: | 
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I have a 1989 Maxum bowrider. The boat is 19.5" in length. Currently it has a 1992 Mercury 150hp outboard on it. The motor seems to be throwing up to much water when on a plane. The boat originaly came with a 120hp Force motor. I appears as though the foot of the motor is throwing up the water. I am concerned about he motor getting saltwater in it from the constant splash. I think the motor may need to be mounted higher. There are mounting holes that would allow me to mount it higher with some work.
Are there any rules of thumb for mounting motors? Where should the prop be in relation to the bottom of the hull?
Currently when sitting idle in the water the waterline is about 4-5" from the bottom cowling of the motor. That seems a little deep to me.
Any insight would be greatly appreciated. Thanks. |
Rick Sweeten
Senior Member
Username: linesix
Post Number: 1124
Registered: 11-2002
| | Posted on Wednesday, March 26, 2008 - 09:51 pm: |
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The proper height is based on the relativity of the cavitation plate to the keel. The cav plate should be no lower that the keel and wants to be as high as possible without cavitating. It is possible you have a 25" engine on a 20" boat. Take a look at the cav plate and see where it is relative to the keel. |
Steven S. Burris
Member
Username: shaneburris74
Post Number: 9
Registered: 03-2008
| | Posted on Thursday, March 27, 2008 - 08:19 am: |
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I checked that out and it looks like the Cav plate is even with the keel. I will have the boat in the water tomorrow and will look at it while on plane (with someone at the wheel ofcourse..ha/ha) Maybe the splashing is not excessive....maybe its just me..I also moved the fish finder sensor because it was causing some splash. |
Rick Sweeten
Senior Member
Username: linesix
Post Number: 1125
Registered: 11-2002
| | Posted on Thursday, March 27, 2008 - 04:12 pm: |
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You can still consider raising the motor up. The less drag, the less fuel burned. |
Steven S. Burris
Member
Username: shaneburris74
Post Number: 10
Registered: 03-2008
| | Posted on Monday, March 31, 2008 - 07:59 pm: |
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Rick,
I think I need to raise the motor..so...a few questions.
First of all, currently the transom bracket sits flush on the transom. there are multiple holes on the bracket that will allow me to raise the motor up. The transom bracket would then have a gap between it and the transom..probably about 1-1.5". Is there any risk associated with this? Obviously it will put more torqe/force/leverage on less surface area of the transom, so in a sense it will be weaker......the bolts however will be in the same location ,but will it even be enough to even worry about it?
Also, what kind of "goop" should I use to re-seal the bolt holes when I re-mount it? Just regular silicone or is there something special out there? |
Rick Sweeten
Senior Member
Username: linesix
Post Number: 1138
Registered: 11-2002
| | Posted on Monday, March 31, 2008 - 08:07 pm: |
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Steve, regular silicone is fine and the gap is not a problem. The holes are there to allow for this adjustment. The added stress on the transom is minimal and, provided the transom is not weakened by rot or a fracture, will not be an issue. |
Steven S. Burris
Member
Username: shaneburris74
Post Number: 11
Registered: 03-2008
| | Posted on Monday, March 31, 2008 - 08:10 pm: |
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Alright, thanks Rick. I'm just gonna back it up to a tree and use a come-along to pull it up and adjust it. It seems pretty simple. Any other tips for me? |
Rick Sweeten
Senior Member
Username: linesix
Post Number: 1139
Registered: 11-2002
| | Posted on Monday, March 31, 2008 - 08:15 pm: |
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Yes, it it doesn't cavitate when you're done, jack it up some more. |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 4259
Registered: 09-2003
| | Posted on Wednesday, April 02, 2008 - 07:37 am: |
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Boat racers have been doing this for half a century, so you're not alone. They call it "adding paint sticks" where a thin piece of wood (after another) is added to raise the motor a bit more. When they get too high--the motor cavitates too much--then they take one out.
Jeff |
