Difference in older(1966) 18HP to a newer 9.9HP?

[cbjfan75]

Ok, I'm sure this has been discussed here before, but I can't seem to find what I'm looking for.
I currently have an 18HP 1966 Evinrude 2-stroke and want to get a more modern 9.9HP for the local under 10HP lake. What I am wondering is do I need to keep my current motor for when I want to go to the unrestricted lakes/river or will there not be that noticeable of a difference? I'm also figuring I should look at 2-strokes just based on weight factors?

Boat is a 1971 Ouchita 14' aluminum V-hull.

Thanks!

 

[nwcove]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

if your 18 is in good working order, the 9.9 would be about 40% less power. ( and yes....thats accounting for the 1966 being rated at the crank, and a modern motor being rated at the prop.)

 

[ondarvr]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

You will see a big difference in performance.

 

[cbjfan75]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

You will see a big difference in performance.

In that a 9.9 will be that much weaker?

 

[kfa4303]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

Yes, the 9.9 will be much less powerful. It will still push you along nicely, but it probably won't get you up on plane. Modern 4-stroke motors generally don't have as much low end torque either, so their power doesn't really kick in until the higher rpms. They're also heavier and more complex, but they tend to be very quite, use less gas and have low emissions. Of course, lots of folks in the forums use vintage 5.5-7.5 hp OMC motors for smaller bodies of water. They're super reliable, easy to work on, cool lookin' and cost way less than a new 4-stroke.

 

[cbjfan75]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

Yes, the 9.9 will be much less powerful. It will still push you along nicely, but it probably won't get you up on plane. Modern 4-stroke motors generally don't have as much low end torque either, so their power doesn't really kick in until the higher rpms. They're also heavier and more complex, but they tend to be very quite, use less gas and have low emissions. Of course, lots of folks in the forums use vintage 5.5-7.5 hp OMC motors for smaller bodies of water. They're super reliable, easy to work on, cool lookin' and cost way less than a new 4-stroke.

Ok, thanks. I've debated on a newer 2-stroke 9.9 or finding a cheaper older 6- 8.5 type. I currently have a 3HP Evinrude Sportwin that I use on the smaller lake that only GPS's me at 4.1 MPH. I'd like to at least be able to get somewhere in the 10-12 MPH range.

 

[nwcove]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

my preference is with the oldies.....my 58 7.5 makes good power. but depending on your personal preference, a more modern early 1980's 7.5 is a good choice. parts are relatively cheap, easy motor to work on, and should get you into the 10-12 mph range. jmo

 

[steelespike]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

The 18 will make about 27 mph with a reasonably light load,the 9.9 about 21.
The 18 would probably plane with 3 or 4 on board if your boat has a generous planing surface.
the 9.9 Will probably struggle with 3.
If your by yourself your 3 might make 6 or 8 mph with a tiller extension to get you in the middle seat
and you pare down extra weight.

 

[cbjfan75]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

my preference is with the oldies.....my 58 7.5 makes good power. but depending on your personal preference, a more modern early 1980's 7.5 is a good choice. parts are relatively cheap, easy motor to work on, and should get you into the 10-12 mph range. jmo

Thanks for the advice/info. My biggest preference is that it has to be at least modern enough to have a fuel pump and use a modern style tank. Starting to find several 6HP Evinrude's on the market that are in a more reasonable price range for me than the 9.9's I am finding.

 

[cbjfan75]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

The 18 will make about 27 mph with a reasonably light load,the 9.9 about 21.
The 18 would probably plane with 3 or 4 on board if your boat has a generous planing surface.
the 9.9 Will probably struggle with 3.
If your by yourself your 3 might make 6 or 8 mph with a tiller extension to get you in the middle seat
and you pare down extra weight.

The best I've GPS'd the 18 at so far is 22.8MPH with the 19MPH range being the norm.

 

[nwcove]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

a well maintained 6hp will do it, but as mentioned, a 7.5 is a better choice. i would personally avoid any of the 8hp omcs. jmo

 

[cbjfan75]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

a well maintained 6hp will do it, but as mentioned, a 7.5 is a better choice. i would personally avoid any of the 8hp omcs. jmo

Not really running into many of the 8's anyhow. Seems to be the 6HP OMC variety and 7.5 Gamefishers. Not knowing much of anything about those I've kind of avoided even considering them.
Have wondered how well this one would work out:

10hp evinrude sportwin eng. s/t

 

[nwcove]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

thats a nice clean looking motor.....with the basic compression test, and gear oil check.....it may well be a good option. even if needs coils, impeller and a carb kit!! easy to work on, cheap parts and good power.

 

[steelespike]

Re: Difference in older(1966) 18HP to a newer 9.9HP?

The best I've GPS'd the 18 at so far is 22.8MPH with the 19MPH range being the norm.

A new 18 was rated for about 27 mph.The one I had was a new 61 on a big 15 ft kit boat with a broad almost flat bottom.
The speedo routinely indicated 23-25 and on a few rare occasions almost made 27.Of course the 23-25 was probably closer to
reality.
actually got it to plane "once" with 5 adults aboard.
I think a OMC 3 is rated for about 8 mph and the 5.5 about 12.Not sure about a 7.5 but old 10hp was rated at about 21.