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Seems too easy

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audiodoode

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"Greeting & salutations, o

"Greeting & salutations, one & all.
I have a 1988 DT115 & I've heard through the grapevine that merely exchanging the carbs, fuel pump & oil pump with a DT140, you have made your 115 into a 140.
I've also heard that DT140's are a bit thirstier than DT115's.
Also that it seems a bit like an underpowered 140 HP.
Is this true, or is there more to it than that?
I have a chance to do this, but don't want to just spend the money unnecessarily.
Thanks for any light you can shed on this subject.<font face=""symbol""></font>"
 
"Alot of models share their po

"Alot of models share their powerhead with a range of horsepowers. I don't have the specs on your particular model, but have done upgrades to a number of motors because guys always want more horsepower.

Despite my recommondation that they save their money, I have gone ahead on many occasions and they have been disappointed like I told them they would be.

Yes, most times the upgrade is as simple as changing carbs, maybe an exhaust plate, sometimes the timing and a couple of other minor items.

If you get the parts basically for nothing and do the work yourself it "may" be worth it. If it is going to cost you, forget it - save the money for gas to enjoy the boat.

Depending what rig you have that particular motor on, the switch from 115 to 140 will result in maybe a 3mph gain, under absolutely ideal conditions - and additionally may require a new prop (and the cost involved with that).

Add up all your costs and then divide it by 3 (for the mph gain) and see what each mile per hour is going to cost you. Then take your current expenditure for gas and increase that by about 20% (how much more the 140 will suck out of the tank).

If you want a real gain you will notice, sell your 115 and hook a 175 or 200 on the back - you will notice that. The 140 would only disappoint you...."
 
"Thank you much Graham.
This

"Thank you much Graham.
This outboard has been very good to me, and if a minimal gain is what is expected, I'll expect to leave it as is.
Thanks again.<font face=""symbol""></font>"
 
"I really would leave it alone

"I really would leave it alone. It's almost never worth "hopping" them up. Like I kinda eluded to, if it's possible on a given model and say your carbs were toast anyhow (required a total replacement), then maybe why not.

But most motors that I've done for guys is "just because it can be done". And really, unless you lie to yourself, you won't notice any gain - not like you would expect.

Going from a 115 to a 140 (if possible) is what a 20% gain in horses. May sound like alot but on a given hull going from a 115 to a 175 (over a 50% horsepower increase) only get's you an extra 6 or 7 mph. Once you get to a certain point, major horsepower increases have little overall effect on the performance of the boat (at the top end anyhow, which is how most guys gauge it).

What is more noticable is say going from a 4 to a 6 cylinder - you will notice that in the low end since the 6 just cranks out the torque.

In some instances more horsepower is good. I have seen (gallon per hour) tests on a pair of Grady-Whites. Identical hulls, rigged the same - one with a pair of 200's the other a pair of 225's. The 225's actually got better gas mileage at cruise speed - they didn't have to work as hard as the 200's.

But every "rig" is unique and before any modifications are made it really is best to do all the "technical homework" to see if 1) it's viable and 2) it is acually going to make a difference.

In most cases the time to figure that out is "before" you hang the motor on the back. After the fact costs way too much to change or correct..."
 
I did the carb swap on my DT11

I did the carb swap on my DT115 and it worked well but unless you fit a coarser pitch prop you won't get any gains execpt accelleration and fuel bills. Go up 2" on pitch and you will cruise at lower revs or faster for the same revs.

Do your WOT tests to get the pitch right.
 
"Oh yeah, forgot to mention, t

"Oh yeah, forgot to mention, the engine internals are the same so I didn't swap oil pump or fuel pump, set oil a bit on the high side if you're worried. The fuel pump delivers more fuel than the carbs need anyway so no need to change that either."
 
"Thanks Andy.
After hearing

"Thanks Andy.
After hearing the doom & gloom gas price forecasts, I may hold off for a bit.
The way it's running right now, I may regret it. I think I have to start a new thread to see if someone can let me know where to start with my latest problem du jour.
Thanks again for the info, I may well end up going that route in the near future.}"
 
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