Johnson Motor Height

carbineone · Feb 22, 2010

Hi everybody,I kinda asked about this in another thread but it pertained to something else so I thought I would start a new one to get your opinion.The Motor is a old 1963 Evinrude that I going to attempt to run on my little late 60s GW Invader 10 foot Speedboat..I raised the motor about 3/4 of a inch and the dowel is running true with the keel I think you call it.I just call it the boat bottom but anyway how does this height I have look to you now?The cavitation plate is I would say a 1/4 inch lower than the boat bottom now.Do you also see any problems at this height concerning cooling intake?I have the new waterpump kit installed so thanks to all who helped with advice on that also.. Thanks Bruce

subtleaccents · Feb 22, 2010

Re: Johnson Motor Height

The cavitation plate should be even to 1/4" above the bottom of the boat.
(Keel)

ezeke · Feb 22, 2010

Re: Johnson Motor Height

Ideally, the a/v plate is just above the water when on plane. Therefore, you would need to raise the motor until the a/v plate is at least even with, or slighty higher than the bottom of the boat.

Madfisherman · Feb 23, 2010

Re: Johnson Motor Height

I agree with ezeke & subtleaccents, how thick is that dowel? Looks like 3/4 to 1" thick & a quarter inch down to the av plate, I'd say you're looking at 1 maybe 2 holes to raise it.

carbineone · Feb 23, 2010

Re: Johnson Motor Height

Thanks.That dowel is 3/4 inch.So maybe I should raise it another 3/4 up maybe?One person here told me with these old Johnsons the way the water inlet is situated you have to be careful not to get it too high and have water intake problems.If you think it will be OK to go a 1/4 inch above I can do that easily enough...Bruce

tashasdaddy · Feb 23, 2010

Re: Johnson Motor Height

you have an old style lower unit, they were a 17 and 22 inch leg, it was designed to be longer, so that the water pick up stayed in the water. raise no more than 3/4 inch. you water pick up is on the front edge of the fin just above the prop.

carbineone · Feb 23, 2010

Re: Johnson Motor Height

Tashasdaddy so you are saying no more than 3/4 inch up from where I currently have it or just never 3/4 inch higher than the bottom? Thanks

carbineone · Feb 23, 2010

Re: Johnson Motor Height

Oh I would say the cavitation plate is 1/4 to 1/2 inch lower than the bottom right now.

ezeke · Feb 23, 2010

Re: Johnson Motor Height

You can raise the motor even with or slightly higher without too much concern.

The primary water intake is on the triangular fin just above the propeller, where the propeller forces water into the screen when running.

When the boat is at rest and out of gear, the intake and the a/v plate are both well below the surface as is the secondary intake just above the a/v plate.

The a/v plate will also be well below the water when running in reverse, which is when the secondary water intake is in use.

tashasdaddy · Feb 23, 2010

Re: Johnson Motor Height

the dowel is 3/4 inch. raising it 3/4 inch will make it even with the keel.

carbineone · Feb 23, 2010

Re: Johnson Motor Height

Thanks everybody I got it now,I am kinda slow ya know...Bruce

Johnson Motor Height

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