Mounting new motor -heigth 90hp 4 stroke

[jameservin]

I am planning to install this new 90hp merc 4-stroke (20in)on my boat and want to get right heigth (hopefully) the first time.<br /><br />My boat has (had) ventillation in turns with the last motor (115 inline) and was helped by adding cup to the prop which eliviated "most" of the ventillation-but not completly.AV plate was exactly even then w/hull bottom.<br /><br />Q: Im thinking to lower this motor AV plate 1/2 inch lower than bottom of hull as a start as I know this boat hull is prone to blowout (ventillation). Does this make sence?

 

[jameservin]

Re: Mounting new motor -heigth 90hp 4 stroke

If being 1/2 lower than bottom costs a little top end but improved blowout potential, then I do think its a good tradeoff.<br />Is that what I am looking at?<br /><br />thanks.

 

[rickdb1boat]

Re: Mounting new motor -heigth 90hp 4 stroke

Realize that the new 4-stroke(Even with a little less HP) will most likely be heavier than the old motor. This may make it squat lower in the water to begin with. I would start out even with the bottom and go from there.

 

[jameservin]

Re: Mounting new motor -heigth 90hp 4 stroke

Good point rick. Thanks. <br /><br />Just a little weight difference-think 373(~) compared to 325 + tilt/trim (inside). Close.<br /><br />Im just unsure what 1/2" below equates to for speed loss.

 

[Dhadley]

Re: Mounting new motor -heigth 90hp 4 stroke

Great advise. Also factor in what prop your going to run. Some props demand a higher X dimension than others.

 

[jameservin]

Re: Mounting new motor -heigth 90hp 4 stroke

This motor did come with a merc 19P 3 blade so i plan to breakin with it, then post the WOT & change prop if needed.<br /><br />Like to run a 4-blade SS soon though. <br />Prob. best to set it even and move later if needed when I change props.