Need ideas to stop porpoising?

[Tarpun]

My fuel filter is mounted on the transom inside of the access door beneath the starbord side stern cooler/baitbox. The fuel transducer mounts next to it. On my application I just fed the cable under the deck back to the console. The transducer cable is the only wire that needs to leave the console and it's about the size of maybe #10 wire. You could bundle it with your motor harness or at least feed it thru the same access.

[diver429]

Well maybe you guys can help me with my problem. I have a 1984 Seacraft Sceptre hardtop with a 1999 200hp mercury optimax. I would like to keep this motor on the boat until I can afford a new honda 4 stroke. I have the motor mounted on a armstrong bracket. I know I have to raise it 1-2 holes after speaking to a tech from armstrong brackets. My problem is also a prop. I need a different prop. Im running a 14 3/8 x 15 ss prop and Im not getting the rpms or the speed that Gary was getting with his 200 mercury. At cruise I have to run 4600 rpms just to go 25 miles an hour. At wide open throttle I get 5400 rpms and get 35 miles an hour. The motor is rated for 5000-5750 rpms, and I would like to get as close to that 5750 number. Will that 4 blade rev prop help me in my situation. Keep in mind the weight of the hardtop and the radar arch. At this time I know I have the wrong prop and I know I have to raise the motor either 1 or 2 holes depending on the measurement. So any input on this would be appreciated guys.

[McGillicuddy]

Based much on what has been well documented on this site, I'm gonna guess that you'll pick up some of those rpm by raising the motor. Start there. 1 hole at a time or whatever to takes to get the anti-cavitation plate 1 to 1-1/2" above the bottom of the hull with the a-c plate parallel to the bottom of the hull. Seems to be the magic number...

I don't see a 200 optimax having trouble turning that prop but as it's said some props are easier to turn than others. What is your prop style/model? Based on what's out there for that motor the your current pitch is about as low as you can go, I think any thing lower will will likely be detrimental to your overall performance.

Tend to the motor height first. You may find yourself pleasantly surprised. Keep in mind your full windshield and top and radar add considerable drag compared to Gary's walk-around windshield. I think if you pick up the rpm and squeeze another couple mph you're smiling. Good luck! Post your results, like to here results.

[Fr. Frank]

Gilly's right. Raise the motor to pick up rpms. You could get an extra 200-400 rpms by doing that. Of course, you might not, too. But you will gain something.

35 mph WOT in a Sceptre with a hardtop running a 200 Opti is good numbers. 25-26 mph should be your normal cruising speed with that motor. I recently sold a '74 Tsunami with an '89 225 Looper Johnson, no hardtop. I ran WOT at 5400 rpms, and 37-38 mph with the bimini down. Bimini up I could only get 34 mph.

[diver429]

Thanks for your input guys.The boat is on land now, and just yesterday I went down to the boat to cover it before the storm and I took some measurements. I put a straight edge on the bottom of the hull extending out to the cav. plate on the lower unit and I measured 2 1/4 inches from the bottom of the hull to the cav. plate. According to the tech from armstrong he said for every foot your motor is away from the boat you have to go up 1 inch from the bottom of the hull to the cav plate. My motor is 38 inches away from the boat, so according to my measurements I should be 3 inches above the bottom of the hull. Right now the motor is 2 1/4 inches so that tells me if I go up 1 hole then I should be at the exact height. Every hole on the motor is 3/4 inches apart. So I m going to raise it up 1 hole and hope for the best. The prop is a mirage prop 14 3/8 x 15. And you guys think thats the right prop. I guess after hearing the numbers that gary was getting with the walkaround I was hoping to get atleast the high 30,s out of the motor at wot. But like you said frank that hardtop and radar arch has some weight to them. any more input would be appreciated, thanks guys. Peter

[Fr. Frank]

...that hardtop and radar arch has some weight to them. any more input would be appreciated, thanks guys. Peter

It's not the weight so much as it is the wind resistance, although the weight does matter. The hardtop is like deploying a parachute behind you to slow you down.