Is this normal performance?

**tahiti460** · 06-23-2009, 01:04 AM

This is my first jet boat,I have had it out twice now.

Its a 18" 77 Tahiti with a jacuzzi wj and a 460 ford with a cam. With my GPS I am getting 51mph and 4000RPM maxed out. Does that seem right or should it have a little more on top?

**455maveric** · 06-23-2009, 01:23 AM

4000 rpm and 51 mph sounds pretty good

**455maveric** · 06-23-2009, 01:24 AM

4000 rpm and 51 mph sounds pretty good

**455maveric** · 06-23-2009, 01:24 AM

4000 rpm and 51 mph sounds pretty good oopps trip post

**SS-201** · 06-23-2009, 07:14 AM

Thats about right for a stock 460 Ford. Be sure you keep your eye on the oil pressure. It seems to be a 460 problem, when acceleration and long runs. However 4000 rpm seems to be a safe number. Also Fords don't like overheating.

If all his is ok, have fun, enjoy

**pyro** · 06-23-2009, 08:28 AM

It's a jet boat, so the object is to make some noise and throw lots of water.
The performance sounds right on par.

Cool lil' boat...

**OldSleekOlds** · 06-23-2009, 08:54 AM

Originally Posted by tahiti460

This is my first jet boat,I have had it out twice now.

Its a 18" 77 Tahiti with a jacuzzi wj and a 460 ford with a cam. With my GPS I am getting 51mph and 4000RPM maxed out. Does that seem right or should it have a little more on top?

The good old "Jet Pump Performance Calculator" shows a Jacuzzi WJ with an "A" impeller turning 4000 rpm is using 205 hp. If your 460 is making about 200 hp, then all is OK. If you think you're making more power than that (everybody thinks they are) then you have a problem. I'm not a Ford guy, but 4K rpm sounds a little thin to me.

Having said all that, keep in mind that it takes a LOT of hp to make a jet boat go very fast. It comes down to Horsepower, pump efficiency, and hull efficiency. After you get all that as good as possible, it will come down to weight. The heavier the whole thing is the slower it goes.

**tahiti460** · 06-23-2009, 09:06 AM

Mine is a WJ B pump. What does that one calculate out to?

**SS-201** · 06-23-2009, 10:18 AM

Post 1972 460 stock engines are only around 200 hp. 1973 is when all HP went in the toilet for emisions. I have one only to be disapointed in it's performance. However there are performance enhancements to wake it up. There are hundreds of great articles out there to read.
I would assume the person before you has tweaked it and if it runs well and gets you back to the dock, enjoy it.

**tunneljet** · 06-23-2009, 04:41 PM

The B stands for a (B) cut impeller. I would check the timing on the motor and make sure it is set at the proper advance. 4000 rpm is very low, it should be much higher with a B impeller, 5200-300 seems more like it.

**tahiti460** · 06-23-2009, 07:24 PM

From what iv heard jacuzzis "B" is equivilent to berkleys "A" impeller.

**OldSleekOlds** · 06-23-2009, 09:40 PM

Originally Posted by tahiti460

Mine is a WJ B pump. What does that one calculate out to?

WJ "B" @ 4000 rpm = 189 hp

**tahiti460** · 06-23-2009, 09:54 PM

Sounds like I need to do a little modding then haha,it probley the original engine in it yet.

**Rivernut** · 06-26-2009, 07:38 AM

That sounds slow to me. I have a 2,000 pound (loaded) aluminum bass boat with a nearly flat hull, not nearly as aero/hydrodynamic looking as yours. Mine will do in the low 50's @ 4,400 rpm's with a much smaller engine, a small block chevy 350. And I'm dissappointed with my speed. But mine has a weleded-up additional plate on its bottom which before the work would hit mid 50's. Yours must have a very mild cam.

**SS-201** · 06-26-2009, 10:46 AM

If its a stock cam and stock pistons are 8.1. Summit has a cam thats supposed to work well, Summit # 3501. Remember if the timing chain and gear are post 1973 they are 8 deg retard. To wake it up get a timing chain set and sprocket for 1968 - 1972.

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