Performance Improvements possible with newer 4 stroke outboards

[Hounddog]

Up here the new generation of racers are not interested it the old school 2 stroke motors. They would like to use their lap top and reprogram their motor same as they do with their cars. They don't mine throwing lots on money into their modifications. There is a very good supply of rebuildable 4 stroke outboards on the market for them to work with. The problem is there is limited information on what can be done to improve the performance or any OEM or aftermarket parts. Maybe there is not enough market for companies to spend the R&D money necessary to develop the products. Years ago the same could be said about the small Honda cars.
To-day that is a BIG business.
We need find ways to get these new people racing. Are you seeing the same thing in your area?
Any suggestions?

[Ron Hill]

I spent Saturday going over spec sheets "PAWING OVER" A Mercury four stroke head. Simon Motor Sports in San Diego has figured out how to, I think the word is "Flash" the computer, so they can disconnect the revlimiter.

But the motors will still only turn 6,500 RPM's.

My "PROJECT" is "Top Secret" right now, but I will tell you there are many areas that the Mercury 40-60 four stroke can be improved.

I will be "Up Front" with you. The head looks like the flow may well be restricted on purpose. (Need to sell better running motors in the future, you know built in obsolescence).

The value springs may be too weak, and allow the values to "FLOAT".

The exhaust area of the exhaust ports appears to be "Squeezed" down, this me be for pollution reasons, or just planned horse power control.

"My People" are going to run the numbers, and figure out what the cam is and what they think the cam should be.

At this time, I have no plans to market anything for these motors. I am working as a "MIDDLE MAN" with some people than want improved performance and they have the financial backing needed for some development work.

I just wish for you guys in Canada, would look at Texas, Tri Hull's roll cages. Or go to 660 drags. Todd Bucknell's accident, last summer, was not got for boat racing!

I have no "FACTS" other than hear say, but It appears the NEW Tohatsu four stroke has some real power. I have 18 pitch props running on 30 HP Tohatsu four strokes and hitting the rev limiter.

[Hounddog]

Thanks Ron, yes we are alike! We both want to promote our sport. Our Drag group here is finalizing 2 additional 660 Drag races this summer and T Class is included. Any accident where someone is hurt is not good for our sport. There were a number factors in Todd's accident. The weather was one of them. It was BAD! The T racers wanted to race even though the other classes could not. There were a lot of fans at that race and the racers did not want the cancel Sunday's complete race day. I am not sure if a cage would have helped in this accident because the impact was thru the bottom of the hull and not the side.
For the last couple of years I have been working on a Critchfield rework. I have the strong box going all the way to the nose. The boat is carbon fiber construction and now after Todd's accident I am adding another layer to the front section. Two of my other T boats already have cells.

[Tiller guy]

I spent Saturday going over spec sheets "PAWING OVER" A mercury four stroke head. Simon Motor Sports in San Diego has figured out how to, I think the word is "Flash" the computer, so they can disconnect the revlimiter.

But the motors will still only turn 6,500 RPM's.

My "PROJECT" is "Top Secret" right now, but I will tell you there are many areas that the Mercury 40-60 four stroke can be improved.

I will be "Up Front" with you. The head looks like the flow may well be restricted on purpose. (Need to sell better running motors in the future, you know built in obsolescents).

The value springs may be too weak, and allow the values to "FLOAT".

The exhaust area of the exhaust ports appears to be "Squeezed" down, this me be for pollution reasons, or just planned horse power control.

"My People" are going to run the numbers, and figure out what the cam is and what they think the cam should be.

At this time, I have no plans to market anything for these motors. I am working as a "MIDDLE MAN" with some people than want improved performance and they have the financial backing needed for some development work.

I just wish for you guys in Canada, would look at Texas, Tri Hull's roll cages. Or go to 660 drags. Todd Bucknell's accident, last summer, was not got for boat racing!

I have no "FACTS" other than hear say, but It appears the NEW Tohatsu four stroke has some real power. I have 18 pitch props running on 30 HP Tohatsu four strokes and hitting the rev limiter.

I was researching the merc inline 3 cylinders and found info suggesting they have valve float beyond the factory recommended rpm's.

[88workcar]

I have ported several Yamaha and Merc 4 stroke heads, we have had decent success so far. The valve springs are weak, the ECU mod would be awesome

[Ron Hill]

I have heard, that Simon Motor Sports can "FLASH" the ECU on Mercury 40-60 HP. http://www.simonmotorsports.com/ I'll admit, I don't know what an ECU is. I do know what a rev limiter is.

I've talked to them on the phone, super polite and helpful, though I didn't have very clear questions.

[Fastjeff57]

Typically, valve springs are always an issue in running 4 strokes at high rpm. To hot rod one of these 4 stroke OBs, you'd need to install a higher performance cam, stiffer springs, and possibly lighter valve rain components. I suppose some cam manufacturer out there would develop and sell high performance cams for these things IF the demand was there.

Jeff

PS: Getting on plane with a 'hot cam' could be a problem here. It is for Go Fast boats with high speed propping.

[twzted]

Hate to revive an old thread, but anyone have any more info as far as performance is concerned on these 4 strokes? I have a merc formula race 60 15" and like to get it tuned by simon, Ron hill have you heard of anyone running one by now? what was the increase? Car worker how has the head work done for performance?

[Tiller guy]

I read somewhere that those motors can't handle high rpm's because of valve float. Fact or BS?

[twzted]

Not sure, I have heard 6500 rpm is safe any higher is asking for trouble with the valves. Ill be happy with 6500, they rev up to 6300 stock thats pretty high for a stock 4 stroke. Im hoping someone with more inside knowledge can chime in, id really like to tune it although they claim only 5-7 hp gain and from what i hear the engine at 6300 rpm pushes about 65-68 hp so that would put it into the 70+ hp range and id be happy with that. Its hard to find a new midrange power plant with a short shaft and good gear ratio anymore without piecing old stuff together. Thats why i bought the merc 4 stroke. theres small rapid crafts running them at 65 mph so its respectable, just turn key and go, great on fuel too. In the uk they race these on boats 16' 1200+ lbs 60+ mph with merc cleavers. some actually run Hills props too.