1988 rinker fiesta vee 250 prop questions
rinker88fvtwofifty
Member Posts: 25 ✭
So I have bin working on this boat for some time now and have found out a lot thanks to ppl iV talked to. So long story short I seemingly have a rear yet never really heard of set up for the yr and make. But was a factory option so 1988 fiesta vee 250 with a 7.4 l 454 meg with a bravo one drive 365 pH to the prop got this info based on paper work I had got on the boat and Merc directly via the serial numbers . With that said I'm now having problem finding the proper prop I went by the manuals and bot a 19 tried it too small then went to a 22 witch seemed way better but rpms are still a bit low don't want to by another prop less it's the proper one. So does any one happen to no what prop I should have ???? According to paper work on the mother and prop that set up likes to run at 5800 rpm to 6400 rpm I thought this seemed odd ?? Hope some one could shed some light on all of this thanks In advance...
Comments
If your HP numbers are correct that year of 454 must have been worked on a bit as stock I think they ran about 330HP and at about 4200-4600 RPM.
I recommend that you make sure what the proper RPM band should be for the engine you have. 5800 - 6400 RPM seems quite high to me, but then I still have a lot to learn!
Once you know for certain the proper RPM band at WOT..... do what you have already been doing - load the boat the way you will normally use it and run it up to WOT to see where it reads.
As I'm sure you know, increasing pitch by 1" drops RPM by 200, decreasing pitch by 1" increases rpm by 200 as long as rake, cup and diameter remain the same.
Please post your findings as I'd be very interested how this turns-out!
The 365hp was designated the 454 Magnum.
It's a bit confusing when going back as 1987 the 454 Magnum was only 330hp, packaged with the Alpha One. '87 and earlier, what was called the 330 was mated with the TRS and to add further, the old 370 was basically what became the 365hp 454 Magnum
More confusion! Just got off the phone with a buddy who was heading-out but had a couple of minutes.
He has had a number of marine 454s in the past. He said - IF I heard it all correctly - that 87/88 saw some "confusion" with Magnums. Some 330HPs were called Magnums and some 365HPs were called Magnums. There was even serial number confusion.
They looked alike but the 365s had rectangular port heads and aluminum intakes and bronze water jacket inserts as well as different cams. They also had mountings for Quadrajet or Holley pumpers.
Like we thought, the key will be for you to find out exactly what you have which will give you the proper WOT range and allow you to prop the boat correctly. He said a decent marine tech should be able to tell you what you have.
I don't know if this helps but it will be neat to see what you find-out!
FWIW: Friend just called me back from car cell phone. Said you're lucky to have the B1 because the magnums were hard-on the Alphas. He thinks there should be an engine serial number on the block near the starter. If you have the 365Hp he thinks you would have 4 bolt mains, steel crank, 7/16 rod bolts and forged pistons. You may get info at Boat Info - Mercury Service Manual nr 9 - 1985-1988 V8 engine.
Sometime in the late 80's (I believe) industry standards for how marine engine HP was measured changed. They started measuring HP at the prop as opposed to at the crankshaft as it had been in the past. This caused the rated HP of some engines to go down. As MT said, the best thing to do to determine the actual HP of the motor is to verify it by using the serial number of the engine.
Frist, a question. Did you verify that with your engine's serial number that your WOT range should be? I "think" it should be 4400-4800. That is, imo, the most important piece of information.
Some guys want to know the gear ratio of their outdrives (I think there were three available for your vintage drive) BUT imo you don't have to know the gear ratio of your B1 if you know the WOT RPM range of your engine.
Let's just say the proper WOT RPM range is 4400-4800...... I'd put that 22" pitch on again and see where the RPMs fall. If low decrease pitch, if high add pitch.
If you suspect your tach is inaccurate borrow a shop tach to use for the trial.