75 hp starflight mounting question

[bdmack]

my 60's starflight is confusing me. if the cavitation plate is immediately above the propeller, why is there a water intake above the cavitation plate. if i mount it so that what i am assuming to be the cavitation plate is flush with the bottom of the hull, will it not be running dry when it is running on plane. it appears to be a long shaft unit, and I have been running it on my 14' 1958 reinell jetabout which has about 18"'s of transom height. the boat has an awfull time getting up on plane, and when (or i should say if) it does get up on plane it is a very wet and jarring ride. I have tried all the trim holes, different weight distributions, etc. I made an aluminum bracket to lift the motor, (5 inches would flush out what I think is the cavitation plate with the bottom of the hull), but am worried that i am running up the wrong tree. Do these motors simply sit lower than other models in the water????????????
help is appreciated....
can i lift it up?

 

[tashasdaddy]

Re: 75 hp starflight mounting question

a 75 on a 14 foot boat is an awful lot of hp. my 14 ft, is rated at 50hp.

 

[bdmack]

Re: 75 hp starflight mounting question

maybe it is a 16? regardless, i can hardly get it up on plane. the motor seems to be bogging out and running rich until the point that it achieves plane, and then it seems to run just fine. once on plane, it is very rough in any wake and a lot of water shoots off the bow into the boat. the boat has a round bottom.

 

[jimmbo]

Re: 75 hp starflight mounting question

OMC did make their motors with longer mid sections(about 2 inches) so as to put the prop deeper in the water. The owners manuals of the time said the inlet above the vnetilation plate was there to let water in when engine was in reverse. As for the poor acceleration, start with a compression test. If good a carb cleaning, points, and carb/ignition sync. What prop is on it; 10 x 11, 10 x 12, 10 x 10, 10 x 9 1/4. or 9 1/2 x 10?

If the boat is plowing at all trim adjustments and loadings, perhaps it has a hook?

 

[bdmack]

Re: 75 hp starflight mounting question

i have rebuilt the powerhead, carbs, set the timing, put in new points, new cap, new wire, and have a 10x11....what do you mean by hook? it feels like it is trying to drag a barge upriver

 

[jimmbo]

Re: 75 hp starflight mounting question

A planing hull bottom should be straight the last several feet before the transom. Any deviation is called either a rocker or a hook. A rocker is a convex curvature of the hull infront of the transom and makes a boat that likes to porpose and a hook is a concave curvature which makes the stern lift and the bow to plow.

 

[bdmack]

Re: 75 hp starflight mounting question

i had just removed and repainted the boat, fixed the transom, and the rotten floor. it seems to have had this problem since i bought it, before and after all the boat and motor repairs. visually the boat bottom looks very flat in front of the transom. i have not taken a straight edge to it, but i do have a fairly well trained eye. are you thinking the motor height is not the issue?

 

[Evinrude Boater]

Re: 75 hp starflight mounting question

When you're reversing the water line is above the reverse intake. When on plane the water is splashing up to the next horizontal plate at the water pump level. If you're having problems accelerating then maybe your motor isn't performing at its optimum.

 

[bdmack]

Re: 75 hp starflight mounting question

when my boat is sitting still, the exaust port sits about 1' out of the waterline, maximum. at 30mph the water is still over the what i will call the "anti-cavitation plate" located not directly above the propeller, but another step up. (the one with the reverse water intake screen that has three flat heads securing it). at thirty, it looks as though if i were to stop, the motor would be submerged, though that is not what happens if i rapidly drop throttle. once on plane the motor seems to have plenty of power and can maintain speeds between 18 and 30/35 mph. to get on plane, i either hit the right wake of another boater, or get myself and passengers to lean in front of the steering wheel. i tried adding a six gallon tank to the front, which helps to get on plane but does not solve the somewhat unsafe feeling the boat has to it. hmmmmmm. sledgehammer? by the way, i picked up an older evinrude without the electric shift for parts that i want to unload. if you need anything off of it, let me know...

 

[bdmack]

Re: 75 hp starflight mounting question

hello again. I guess my basic question with this motor is, what is the proper mounting location? What would be considered the cavitation plate on this thing, as there appear to be two potential candidates? The little one above the water intake, or the one directly above the prop? Thank you for you help!!! I seem to need it...

 

[Willyclay]

Re: 75 hp starflight mounting question

The "anti-cavitation plate" is the BIG one directly above the prop. Reading your posts sounds to me like you have a long-shaft (20inch) motor on a short-shaft (15inch) transom. The starting point for mounting the motor would be to get the plate parallel with the bottom of the boat and about 1inch or 1.5inches below the keel. Good luck!

 

[Evinrude Boater]

Re: 75 hp starflight mounting question

Bdmack, send me an e-mail and I'll forward you some photos of my set-up.
semenuk1@hotmail.com