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Aquahaulic
05-17-2001, 01:55 PM
I have a '90 Arriva 20' With the 5.7(260hp)Merc. AlphaOne and through hull exhaust.When I got the boat it had a 21p ss prop. It took forever to plane out,wouldn't turn over 3300 RPM and topped out at about 30mph. I had to drop down to a 17p prop. Now it planes out a bit better but but still only runs about 43mph at 4900rpm . Does anyone have any Ideas on what could do to get better performance out of it? I just thought it would run better than it does. This my 1st boat and any help is appreciated .

B-rad502
05-17-2001, 08:17 PM
What rpm are you at with the 17 pitch prop??

ponponracing
05-17-2001, 09:16 PM
Your 20 footer is pretty heavy for getting performance from a small block Chevy. I'll tell you what I do when a customer shows up and want more speed from it's rig. First of all, try a four blades prop (Mirage 2 is good or any brand is as good or may better). Just make sure the max recommended RPM is reached. Normally, your boat should go on plane easier and faster. Your top speed won't be lower, but it may be a little be faster (may be, problably). On plane is for sure but top speed is so-so. With a four blades, at lower RPM, you will go faster compared to a tree blades, loaded or not.
Then you will want to save the more power from your engine to use it for speed: get a good set of exhaust manifolds, that's a sure bid. From the stock Merc exhaust manifold, you'll gain a few MPH by adding a set of log manifolds or those new cast manifolds from Keith Eickerd, or even better, jacketed headers. You didn't mention about the engine condition or the boat weight. First, try what I said and then write again to my attention. If you want to invest a few bucks on this engine, I a have few hints, but first try what I said. We are talking about 3-5 MPH max. If you definitly want to get a lot more from your boat, think about a 365, 420, 502 or even bigger motor. In boating, power is the key to speed. "The best way to spend a fortune without knowing where it goes is in boating". Signed many football, basketball,hockey players, movie stars and my girlfriend.

ponponracing
05-17-2001, 09:34 PM
P.S.: Golf is a slow sport. Although whealty, those stars don't know about how to spend those millions. When they will find out about bathing suits, they will buy boats. Even Formula One drivers found out. Cart series drivers are knocking at the door.

Racing Ray
05-18-2001, 06:25 AM
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[This message has been edited by Racing Ray (edited March 12, 2002).]

ponponracing
05-18-2001, 08:58 AM
Ray,
honestly, I could never make a comparison between those two brands. Just by looking at the pictures, I can guess that the Eickert manifold is more like a headder than the Imco. I am talking about the Imco Powerflow Plus. I personally met Keith Eickert in his Florida shop a few years ago and I was very impressed by what I could see. Keith Eickert is a highly respected man in high-performance. Visit www.keith-eickert.com. (http://www.keith-eickert.com.) Have you ever heard about Hi Power Stainless Marine? It's a headder inside a manifold-type box. I sold one of those on a small block Chevy and it gave the same result as a dry car headder. Visit www.hipower.ca, (http://www.hipower.ca,) click on 5.7 or 7.4 lt Chevy Mercruiser.

Aquahaulic
05-18-2001, 02:49 PM
Thanks Ponponracing, I am going to try a 4 blade prop tomorrow.
The engine seems to be in good shape ..haven't checked compression on it but plugs, timing and ignition sys. are ok. It looks as if the previous owner had opened the engine(wires and brackets are marked)but I don't know what was done.Just doesn't seem to be building power like it should.