Replacing and inboard with an outboard

[Lazysailer]

Hi All,


I'm new to this forum and sailing and have had some bad luck with my inboard 8.5hp yanmar engine. Pretty sure that I've bent an intake valve by getting water back in to the cylinder via a holed water cooled exhaust. Anyway I've removed that engine and have mounted a plate and outboard mount on the back so my next step is to purchase an outboard.

So my question is, if I had an 8.5hp diesel inboard, will a 8-10hp outboard give me the same speed? I used to be able to cruise my 26 foot endeavour at about 4 maybe 5 knots with a clean hull. I know it won't be as economical as the diesel but that's ok.

 

[Lake Superior Sailor]

The smart thing to do is to take the yanmar to the shop and have it rebuilt then put it back anything else is a mistake!..Dale

 

[Benny17441]

We would have advised against the conversion but seeing that you have already commited to it we wont go into the subject. Lake or coastal? For coastal waters I believe you will need at least a 15HP outboard engine to equal the performance of the inboard diesel. Get a long shaft engine to minimize the ocurrence of the prop pulling oiut of the water. Perhaps for a lake with calm waters you can use a 10hp but would still recommend long shaft. Remote controls at cockpit would be a convenient addition. Do not forget to properly clean and vent the fuel tank.

 

[djplatt]

What does your boats displacement?

 

[Lazysailer]

Not sure of displacement think its around 1.25 ton?? but I have about 4 foot of draught.

 

[Lazysailer]

Yeah and I will fix the inboard but I live in a remote part of Australia and there are no marine facilities here. I've pulled the motor out and got it up on deck (huge job in 35 def heat) the intake valve is bent and the water cooled exhaust is totally knackered and requires a whole new one. So that's another project in it self. In the mean time I was hoping to get a tohastu 9.8 hp and attach it to the back to keep me sailing. Other wise I have an out of action yacht for ages. I didn't buy it last year just to sit there.

 

[LloydB]

Welcome to SBO. Based on past discussions and my OB I think that 9.9hp should be fine unless you are over 10m and sailing on a fast river and need to catch the mooring in a heavy wind. BTW 35deg seems enjoyable
Elev: 259 ft; Latitude: 45.00459N 122.7830W
18 Jan 9:03 am PST 28*

 

[FourPoints]

Not sure what year yours is, but assuming this is it, it's 4,500lbs
http://sailboatdata.com/viewrecord.asp?class_id=5948

general rule of thumb, 2hp per 1000lbs displacement, then add another 10% if you want to cruise at / near hull speed in mild chop or into the wind, or if you have a full keel.