My boat is rated for 3kw/4hp can I do 5hp?

[jkru]

So I have a Silver Marine dinghy with a flat bottom with slats; It says max 3kw motor. What is the danger of putting say a 5hp on it (according to my rating overpowering the raft)?

The motors that I want only come with option for 2.5 and 5hp and the 2.5 is a bit under powered with two adults and a child in the dinghy (satisfactory but slow).

Thanks for the help!

 

[jkru]

Re: My boat is rated for 3kw/4hp can I do 5hp?

Actually there are a lot of threads on it so sorry for the duplicate. Seems the answer is: Who the hell knows for sure

http://forums.iboats.com/non-repair.../overpowering-my-boat-who-believe-342480.html

 

[tpenfield]

Re: My boat is rated for 3kw/4hp can I do 5hp?

Yea, I have a motor that is going to be a bit much for my dinghy. Just be careful. 25% more power is not going to amount to much in terms of speed, etc.

 

[Sea Rider]

Re: My boat is rated for 3kw/4hp can I do 5hp?

Which brand 2 or 4 strokes engine are we talking about ? Generally both 4HP and 5 are same size, weight, just carb restricted. Not an issue to place a 5 if that were the case.

Happy Boating

 

[jkru]

Re: My boat is rated for 3kw/4hp can I do 5hp?

I actually wanted Lehr because I do not want to carry fuel, do not want to pay torqeedo money etc. The 5hp is actually over a inch narrower and will fit better in my transom. It is propane 4 stroke I believe.

Thoughts? 3kws is actually 4.02306627 horsepower so .02 more wiggle room.

 

[Sea Rider]

Re: My boat is rated for 3kw/4hp can I do 5hp?

Yes it's propane, for a long outing will need to buy many spare propane bottles or carry a bulky propane tank along. Not an issue being 5HP over a 4. Besides Lehr only manufacturers 5 and up.

Happy Boating

 

[jkru]

Re: My boat is rated for 3kw/4hp can I do 5hp?

Yes it's propane, for a long outing will need to buy many spare propane bottles or carry a bulky propane tank along. Not an issue being 5HP over a 4. Besides Lehr only manufacturers 5 and up.

Happy Boating

Thank you for your response!! I just use it for little island hop and taking my son for a spin so works great on the small 8' dinghy for me. The 2.5hp was a bit under powered and ironically wider than the 5hp and did not fit nicely in the transom.

One more question here is the fuel consumption:

Here are the burn rates
LP2.5
@4000 RPM .24 gal/hr 1 HR
@3000rpm .10 gal/hr 2.5 HRS

LP5.0
@4600 RPM .50 gal/hr 30 MINS
@3000rpm .22 gal/hr 1.4 HRS



is this to say that 5hp at 3000rpm I can go twice as fast and far? So 2.5hp vs 5hp even though I only have 1.4 hours of fuel I can go twice as far or it doesn't work that way

Sorry if these are kind of newb questions.

 

[fbpooler]

Re: My boat is rated for 3kw/4hp can I do 5hp?

No, it does not work like that.

 

[colbyt]

Re: My boat is rated for 3kw/4hp can I do 5hp?

I hate to see people make costly mistakes. Consider the extra weight, the turns at higher power and a dozen other things before you make the jump.

Tohatsu makes a 2.5, 3.5 and 5. About an hour at WOT and much better at 3/4 throttle. If the 3.5 moves my 14/48 tin and 600 pounds of people it ought to make a dingy fly.

 

[jkru]

Re: My boat is rated for 3kw/4hp can I do 5hp?

Weight wise it is only 37.9 lbs vs 49.6 so 11.7 lbs and fuel wise its the same 16oz canister and if I go with composite tank for propane its nothing.

I think the total weight for me with wife and kid would be 380lbs plus about 120lbs max for boat and dingy so 500lbs tops. It does not have a keel its a flat bottom as well. I wouldn't mind it to fly once in a while but for the most part a couple knots is fine and I am hoping to get a good 2 hours out of a canister at that speed. (Similar to the 2.5hp)

 

[tpenfield]

Re: My boat is rated for 3kw/4hp can I do 5hp?

I got a 7.5 HP for my dinghy :noidea: figured it might move right along . . .

 

[jkru]

Re: My boat is rated for 3kw/4hp can I do 5hp?

I got a 7.5 HP for my dinghy :noidea: figured it might move right along . . .

Ok Yamaha 350 it is