Announcement

**TMD** · 02-26-2005, 02:12 AM

Hmm, so you are hoping that by introducing...or allowing more air to access the carb, you will increase in power. Similiar to K&N filters?

Well, it does not work, it just makes more noise.
There is more than enough air supplied to the carbs at any given time.

Even if it did work, the power gain would not really be noticeable.

You would be best to try different styles of props, hydrofoils or even load your boat in a different way.

Has the compression been checked lately?
Engine been tuned up?
^that is where I would start before spending money on anything else.

TMD

**1Chavez** · 02-26-2005, 05:23 AM

TMD, thanks for the reply. I am thinkng along the lines that if there is more air and fuel in the cylinder, I will gain some power. I know it will not be the equivilent of strapping a turbo to it, but I am thinking if I got a cooler, denser air charge (vent the cowling, open up the airbox possibly), power would increase. Engine had the carbs rebuilt last year and there should be no compression issues (I've owned since new and it is very low hour), but I will test before the season. I am looking more to be the fast Whaler on the bay. There is a similar vintage Whaler running an Evinrude that slowly walks away from me at WOT. When I first bought the boat, it had a Johnson on it that was nothing but problems. Needless to say, I talked down Johnrudes, and now a Johnrude is faster than my boat. I was thinking of a jackplate, but that might be overkill for a 70. I might have to find a Yam 90, secretly swap and just keep the 70 cowl, but I'd rather spend the money on the 36' Pacemaker.
-Rich

**TMD** · 02-26-2005, 11:59 AM

This Evinrude that slowly pulls away from you...what is he/she running for a prop?

Now back to the jetting idea and adding cooler air.
I know what you are attempting to do, and yes it sounds like a good idea.
Venting the hood will not hinder the performance of the engine...so if you would like to try it go right ahead, just make sure you do not vent where water can enter. Messing with the airbox might have adverse effects on your engine. The air box is designed to create movement of the air before it enters the carb.

Now lets talk about the weather.

Hot days can reduce the power output of an engine by 10%. This is more noticable with carbed engines rather than fuel injected engines as they are able to compensate for the change.

Your compression reading...what are the values?

Oh, btw. Increasing in speed can be very expensive. 1000-1500per MPH.

TMD

**1Chavez** · 03-06-2005, 03:14 AM

As far as I know their prop is stock, but I could be wrong. One thing I did notice is their engine is up one mounting hole from normal.
I am still considering this project, but it has dropped in priority. If I do vent the cowl, it would be louvered and I would keep water entering in mind.
This idea is still in the idea stage. I would like to get a temp reading inside the cowl as stock for refrence first. As to the compression, I have never done a compression test on this motor, but I have owned since new an it is very low hours. I realize low hours is no substitute for compression test, but with snow on the ground, my motivation to do a compresion test is low. Thanks again,
-Rich

**TMD** · 03-06-2005, 10:47 PM

Please check back and let me know the results.

TMD

Announcement

re jeting 70

re jeting 70

Comment

Comment

Comment

Comment

Comment