porting

[dil/viller]

anyone with knowledge on the following. i bought a merc 500 mod powerhead from a hydro racer advertisement this last december. got the motor and when i inspected the exhaust ports i found they were squared to the point of xposing the cylinder from the north/south ports of each cylinder. when the pistons r at top dead center there is approx. a .050 plus gap. some i guess refer to this as weeping. my ? is will this motor function properly and reach top rpm or will the weeping cause breathing issues? this is a 44ci. ive been told different things on this and am looking 4 some one that has xperienced this first hand or no's for sure one way or another. i have a opportunity to return the motor. thanks in advance for your comments.

[David_L6]

Try it and see.

I've had a motor or two that opened up the bottom of the exhaust ports when the piston was at TDC. I'd rather that not happen but it didn't seem to hurt those motors. They ran just a slow as everything else I've ever had!

[dil/viller]

porting ?

i bought a merc 5oo mod powerhead off of a hydro racer adv. got the motor and when i looked at the exh ports i found the top and bottom ports of each cyl. were squared to the point when the pistons r at top the cyl r exposed by .050 plus. in the corners. ? of the day for those that no for sure. will this type of porting allow the 44 to run properly at peak rpm or will there b a breathing problem?? thanks in adv for comments.

[Racing Fan]

Bump Bump Bump

[Racing Fan]

Bump Bump Bump

[Racing Fan]

Bump Bump Bump

[dil/viller]

can't believe the lack of wisdom on this subject. figured there would be lots of expertise xpressed from the porters of outboard world.

[STEVE FRENCH]

Harry Brinkman Talks about this in hist How to Modify a Merc manual.....I'm not sure but when I find time I will review his thoughts on this....Kind'a foggy right now but I think he warned against this.

Anyone have a minute to help this racer.......my wizdom machine is occupided with home prodjects today.............

[jeff55v]

Porting...

Harry Brinkman Talks about this in his How to Modify a Merc manual.....

Harry's book is on eBay right now:
http://cgi.ebay.com/ebaymotors/Mercu...em320336757633



I was waiting for Trident to chime in on this subject. As far as I'm concerned, he's one of the few experts on porting.

Here's what Harry Brinkmans book has on the subject:
"...Bottoms of exhaust ports are important also. When the piston is at top dead center of it's stroke the bottom exhaust side of the piston skirt can UN cover the port and open up the crankcase via the bottom outside edges of the two outside exhaust ports. This is why the 30H Mercury has the two shortened up exhaust ports. When you square out the bottoms of the exhaust ports you can uncover the crankcase at TDC, especially if you widen these ports and especially on the 44ci and 25mod mercs. For this reason CMRS Marine port jobs employ an angle cut on the bottoms so that this does not occur. I HAVE built good fast C engines with square bottom exhaust ports that uncovered the crankcase, so this is one of those areas where you can make your own choice and it may not be important, at least not on 30H's with Quincy pipes."

I hope this helps.

ADD: I strongly recommend Harry Brinkman's book to everyone who does any kind of racing engine work.

[STEVE FRENCH]

Dave mason,
Any exsperienced thoughts on this from..Lyle ?
Alan ported a block the same way and found one used wiseco piston while salvage'n powerheads, that the skirt still coverd....ordered a set and next batch left em open.
Set block on shelf till time alows us to try it ................LOL

dil/viller, will the seller let ya test it?.....Any word/history from him.....or is he a second party seller?

[Morris85C]

Rod give me a call I will try to help you out here got two moters like that morris85c

[Dave M]

Call Lonnie

He has some good expertise, and also some good experience. It all depends on what you plan on running the engine on and what type of courses you expect to race on.

Prop selection and gear ratio come into play with porting like that. Not that they don't porter other ways, but with what you have it will make a larger impact on your end results.

[vislaguy]

i'm the seller

I'm the seller of this motor.yes i offered a refund on this motor but also feel that this is a good motor built by a aof nat champion in d-mod and is now retired but has some very fast stuff.I also feel the motor should be run first before someone should say that the porting style on this motor will not let it run right.Is it a champion motorwho know will it go out and take first every time ,who knows there are so many other factors when putting together a boat setup that wins.the price at which this motor was sold reflects that it did not have some nat championship win in its belt but that doesnt mean its not a great motor in the right hands.It also takes some time to dial in a setup too so even though i recomond running the motor I will not refund after that if it doesnt win races theres just too many other factors envolved.I feel I have been fair in this deal concidering the low cost at which it was sold(divorce sale thanks for everyones input.mike morris .temple ga

[seaward]

I like David L6 response. Try it before you trash it. Maybe it's what works for you. Seaward

[B Walker]

The following is somewhat of a joke:

Anyone old enough to have serious knowledge and experience on this subject is probably too old to use a computer proficiently enough to weigh in on this topic here.

The previous was somewhat of a joke.

hehehe

BW