95 sundancer 250 w/350 MPI Horizon 300HP

[Shaun78]

bravo 3 w/20 pitch props and all I get is 4300 RPM's. What's wrong? I can't drop pitch any lower. Should I be going faster than 36-37 GPS. I thought that it should go 45mph with a 300 engine. anyone have a 250 sundancer and what speeds are you getting

 

[Bondo]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

Hi Shaun,....... Welcome aboard to the forums here at iboats.com................

While I don't have a 25' Sundancer,........
I'd think that a Strong running 350MPI should be pulling 4800rpms or so at WOT.........
That should get you over 40mph,........ 45 might be Wishful thinking,..... Donno.......

Has the motor been evaluated at all,..??..??....
When was it's last Full Tune up,..??......
Have the Filters been serviced,..??......

 

[Shaun78]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

The engine was perfect. 215 lbs in each cylinder. Only has about 50 hours total. The lower drive unit was replaced and then the upper housing(electrolosis issue) Maybe the gearing was wrong when the lower was replaced but even if it was it should tac out at 4,800 running a low 20 pitch dual prop on the bravo 3. I dont think the gearing was changed on the upper(housing only)

 

[Don S]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

What is the SN of your engine? There was no such thing as a Horizon MPI in 95. I think they started in like 01 or 02.
Either way, the MPI engine should get more than that rpm with a 20 set of props. You have something else wrong.
And those engines don't come close to 215lbs of compression. Either you have a bad gauge or maybe water in the cylinders, but with 215 being a consistant number, I would bet on a faulty compression gauge.

 

[Shaun78]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

The cylinders were 210 & 215 lbs. It's not the original ehgine. It was a factory compl assy put into the boat end of 05. The comp readouts were done by the marina end of 06. They winterized it and did a compl workuo on the boat and changed the gimbal, bellows, shift cables etc. I would think the boat should spin a 24 pitch 4,800 RPM's. stock was 250 HP w/ a 22 pitch prop. The only thing I can think of is when the lower unit was replaced that the gearing is messed up or something. The upper was redone also but I think it was just the case replaced due to an electrolosis crack. The boat runs perfect. Maybe the bottom is full of crap from being in the water all season also.

 

[Don S]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

Maybe the bottom is full of crap from being in the water all season also.

If it hasn't been cleaned all summer, then YES, that is probably your problem.

 

[MikDee]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

Well a few yrs ago, I had a 79'-24 foot SeaRay Cuddy (a heavy boat) with a stock 350/260hp Mercruiser, with a clean bottom, synthetic blend oil, carb adjusted fully rich (maximum idle rpm), stainless mag core spark plug wires, new champion plugs, thru-hull exhausts with mufflers, and ran a 17" pitch prop, I was lucky to hit 40mph at 4600rpm fully trimmed out.

I would bet it would take a really worked small block, or a stock big block to hit 45-50 in that boat.

Granted with modern technology, you have a duo-prop system, electronic ignition, & fuel injection, don't know how the weight of your boat compares, but if you actually do have 300hp, I'd guess 45-50mph would be a ball park figure if all is well with your hull, & engine.
By the way, if it's been in salt water, and your bottom is not painted with antifouling paint, you're lucky if you get 36-37mph.

 

[JustJason]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

the gear ratio is done in the upper

 

[MikDee]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

the gear ratio is done in the upper

True, the shifting is done in the lower.

 

[Shaun78]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

maybe the bottom is full of crap. It hasn't been used to much.

 

[Don S]

Re: 95 sundancer 250 w/350 MPI Horizon 300HP

If it hasn't been cleaned all summer, then YES, that is probably your problem.

Posted this earlier.