Need ideas to stop porpoising?

[Fr. Frank]

The OFS4 prop is actually made by PowerTech Props, and is, in my opinion, one of the 2 best props made for SeaCraft hulls. 16" pitch sounds perfect in a 4 blade. It is a heavy stern-lifting prop, very strong blades (not thin), with moderate progressive rake, allowing for a wide range of trim angles. It also happens to be the basis for the prop I ran on my 20' Seafari, although I ordered mine in a custom 3 blade 16.5" P and 15.25" diameter. I had a Merc V6 2.0L on my boat at the time, which was built to produce about 190/200 hp.

The other advice from Tom is about right. You need to get the cavitation plate above the hull bottom so that it doesn't pull the stern down while planing.

[eggsuckindog]

1 thing at a time, looks like 2 holes to me also, then get a WOT RPM reading so you can get the correct prop pitch the first time

[gss036]

They raised the motor 2 holes for me this morning and we ran it for about 1/2 hr. Did not get any porposing and and was able to get 5950 RPMS(range of WOT 5K-6K) out of it w/2 adults and 90 gal of fuel and the extra 60 lbs of lead in the bow, I just took the lead out as I don't think it will be needed now. I did not check the speed but plenty fast, had to dodge crab pots.
I asked about the 4 blade prop and they were not very eager to go there because of the $500+ cost. I even offered to split the difference on the price increase to swap the prop, but all I got got was no comment or we'll see.

[McGillicuddy]

Excellent, now get back to fishing!

[Briguy]

Gosh darn this is one of the best posts as of recent. All awesome, spot on information. What a great community. Kudos to all that posted. Sounds like the dealer is stepping up to the plate. Now, get the lead out!

[gss036]

Went fishing yesterday(did not say catching,bad day, 3 dog fish and 3 lingcod,ling cod is closed). The lead is out and the boat preformed great. Now to work on the prop, I was able to run it up to 6000 rpm/44mph/GPS and still just a touch of throttle left. RPM range is 5000-6000 rpm, I am trying to get them to swap out the prop for a 4 blade as suggested above.

[Fr. Frank]

You want to be able to hit the upper end of maximum recommended with the boat at max gross weight. Load it up with full fuel, max people, and max equipment, and you should be able to hit the upper end of max rpm range.

You should be able to hit max of max at max.

I can hit 5800 rpms with full fuel and 7 people on the boat, along with beach and camping gear in the cabin. I expect to never spin a hub from overloading, or have a shortage of low-mid-range power/torque in an emergency.

[gss036]

Went down south and picked up my new 4 blade prop this AM. Just installed it and hopefully will be able to get out tomorrow or Saturday. I am anxious to see how it performs compared to the 3 blade. Talked nice to the dealer and he ended up taking my 3 blade prop back and we split the difference in the price on the 4 blade Powertech.

[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.