1962 Dorset 17' info required

[davis]

I have a 1962 Dorset Speed Boat with a 4 cylinder Volva Penta inboard/outboard 100 drive gas engine. Does anybody know what the free floating boards? on each side of the outboard are? What is the purpose of these and can they be removed?<br /><br />Boat and motor work great except once in a while it backfires through the carburator. Does anybody know what would cause this? Also, engine has to be above 3000 rpm to plane out which is about 3/4 throttle. Would the free floating boards effect the planeing?<br /><br /> davis.nest@ns.sympatico.ca

 

[Fouled Plug]

Re: 1962 Dorset 17' info required

Are the 'boards' some type of homemade trim tabs? I assume you mean they are mounted on the transom on either side of the outdrive. Sounds kind of wacky from the description. Do you have a pic?

 

[Spidybot]

Re: 1962 Dorset 17' info required

Once upon a time there was some adjustable trim tabs.<br /><br />If the adjusting mechanism is worn they might become all loose and will do zero for you.<br /><br />Abt. Planing: Normally you'd start off at full flat out and once it planes, get off the throttle until you keep a clear plane at reduced speed.<br />Depending on hull design, weight, weight distribution, power/weight ratio, engine tuning, trim setup and prop conditions etc. the rpm and speed at this cruising state varies a lot.<br /><br />Underpowered boats needs relatively more throttle to achieve this, and this is one of the good arguments for using no less than 75-80% of max. rated hp. Rather a larger motor running with ease than a smaller motor struggling all the time. Also much better on mpg.

 

[davis]

Re: 1962 Dorset 17' info required

Trim Tabs are mounted on the boat itself, on either side of the transom about 8" above the bottom of the boat. There is a wing nut on trim tabs to adjust toward or away from boat. Total adjustment is about 4". However, the trim tabs are free floating up or down.

 

[Spidybot]

Re: 1962 Dorset 17' info required

Uhmm... could you post some pictures? Might even make other info pop up here

 

[davis]

Re: 1962 Dorset 17' info required

How far below water line should center of propeller be on a long shaft outboard? Or does it depend on the boat?

 

[Fouled Plug]

Re: 1962 Dorset 17' info required

You will want to start with the cavitation plate level (or as close as possible) to the bottom of the hull. You can play with motor height for the optimum setup after that. Are you converting to an outboard from the Volvo I/O? I'm still curious about your free-floatin' trim tabs.....