Downsize from 200hp to 175hp more efficient?

[willp2]

I recently purchased an early 1980’s 21’ Proline WalkAround with a 200hp Blackmax. The powerhead needs rebuilding and I have heard from the previous owner that the this thing used a lot of gas and had a limited range.

I was wondering if swapping out the powerhead for a 175HP or even 150HP powerhead might get me better range?

I know there are lots of variables, but just wondering if this is something I should consider or is that idea just nuts?

Thanks!

 

[OldMercsRule]

Re: Downsize from 200hp to 175hp more efficient?

Hey Willp2, I would stick with the larger powerhead. Fuel consumption is generally a function of the horse power of the engine. A 150 HP engine will burn about 15 gals per hour @ WOT and a 200 HP engine will burn about 20 gph @ WOT. Both would be about the same weight so you could throttle back the higher HP engine to a lower burn rate to save some fuel. Check Silvertip's posts about MPG here within the last month or so for a very interesting discussion based upon his tests and observations. Some of the newer engines (E-TECH or OPTIMAX) may be more efficient, but lots more $, and from my name you can see how I would come down on old vs new. Hope this helps JR

 

[OldMercsRule]

Re: Downsize from 200hp to 175hp more efficient?

The post you want to read is: "How many miles per gallon?" by Asain320 a couple of pages in. JR

 

[willp2]

Re: Downsize from 200hp to 175hp more efficient?

Thanks for the info. I was kinda thinking that might me the case. It seemed logical that a smaller motor might use less, but you need to use more of its power to get you moving so it would seem you use more. That pretty much defined my confusion..

I'll have a look at that other thread.

Thanks!

 

[Silvertip]

Re: Downsize from 200hp to 175hp more efficient?

Here's the link to that discussion.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=29;gtid=1228266

 

[Chris1956]

Re: Downsize from 200hp to 175hp more efficient?

Willie, It is likely that 150HP is sufficient to push that hull well. I have a 21 Seaswirl dual console, that my 150HP Johnson handles easily. Something to consider is a more efficient outboard. If your motor is cross-flow, a looper should provide better fuel economy, and a bit more zip. If you have more bucks, a 4 cycle OB, or Direct Injection OB have much bettery economy.

 

[jimmbo]

Re: Downsize from 200hp to 175hp more efficient?

All V6 mercs are loop charged. At crusing speeds those motors were suprisingly good on fuel. Going to a lower hp model isn't going to reduce your operating costs much if at all.

 

[willp2]

Re: Downsize from 200hp to 175hp more efficient?

Well I'm convinced, I'll be keeping my 200 and loving it.

All V6 mercs are loop charged. At crusing speeds those motors were suprisingly good on fuel. Going to a lower hp model isn't going to reduce your operating costs much if at all.