SeaRay Seville 180 BR

[benmcclure]

I recently purchased a sea ray Seville 180 BR (1987). This boat has a Mercruiser 4.3L V6, rated at 205 HP. The boats dry weight is about 2000 lb, I would estimate 2500 loaded, plus 2 people at about 300 or so. Alpha One Outdrive, with what I believe to be a 1.81:1 outdrive, this is not confirmed and may be incorrect.

Anyway, the prop on it was pretty beat up so I decided to replace it. It was originally a 14.25 x 19 3 Blade Prop. I am not completely sure of the WOT, the Tachometer stated 4500 RPM, but i am doubting its accuracy.

I Purchased a Michigan Wheel Vortex 14.25 x 18 4 Blade Prop.

Here is my dilemna, with this new prop, the tachometer on the dash hits about 4200 RPM, but I purchased an Actron Multimeter that included a tachometer in it. This Tachometer at times is right on, up to about 2500 RPM, after about 2500 RPM it seems to start to become way off. When my dash is reading 4200 RPM, the actron is reading almost 7000 RPM. I honestly doubt that it is truly hitting 7000 RPM, but it has me scared if it is. I plane out at about 3000 rpm (dash reading, actron reads about 4000), going about 22 mph, but only get up to 34mph or so at full throttle. That would be about 52% slip, which honestly seems incredibly high.

Does it seem that I am that underpropped that I may be hitting 7000 RPM? Its a brand new prop with a brand new Flo-Torq II Hub. Also, is it possible its a bad ignition coil or something of that sort that is causing it to misread?

 

[Bondo]

Re: SeaRay Seville 180 BR

Ayuh,... I'd believe the Tach over the multimeter....

A 4.3l,... Stock,... Will only turn 7000rpms for a Second or 2....

 

[Maclin]

Re: SeaRay Seville 180 BR

The 4200 to 7000 is about the difference you would see if the multimeter is triggered from the negative coil terminal like a dwell meter and is set to 4cylinder 4 cycle (4000 would show as 6000). Some meters like that just have a different scale for each cylinder and cycle combination, no meter settings. If so maybe you are looking at the wrong scale.


4200 rpm at 34mph with an 18 pitch comes out to about 10% slip, so those numbers from the dash tach and speedo make sense.

 

[benmcclure]

Re: SeaRay Seville 180 BR

This one definitely has meter settings. Its set at 6cyl (it doesn't have 2/4 cycle, but since it was designed for cars, I would guess 4 cycle).

Anyway, my thoughts were also that it would not run at 7000 rpm for very long.

Does my prop combination sound incorrect? I am guessing I might need a good tune up and a higher pitch prop. I would guess this boat should be able to make the mid 40's fairly easily.

 

[Maclin]

Re: SeaRay Seville 180 BR

What does the engine sound like?

It seems to me that a good running 4.3 in an 18 footer should be able to hit high 40's with a 21-23 pitch prop at 4400-4800rpm, just a feeling.

Like I mentioned before, the numbers from your dash gauges jive, so I think you are only getting 4200 rpm right now. Those 4.3's like to rev so I would start with a good tuneup and see why it cannot get higher than 4200 with an 18 pitch prop.

If all it can hit is 4200 rpm then that pitch prop is about right. If it can truly hit 4600+ rpm then I would try a 19 or even a 21, either should get you closer 40 or above.

 

[Hoser85]

Re: SeaRay Seville 180 BR

Ben, I used to have the same SeaRay that you have and loved it. I ran a stainless 3 blade 19" for tubing days and would switch to a stainless 3 blade 21" when we were just going out for woo-hoos. With the 21" and lightly, correctly loaded she would flirt with the 51 mph mark @ 4800 rpm.
My advice is to ditch that 4 blade prop and also lovingly install a new set of correctly gapped AC Delco MR 43 T 's. I would also look up the oil specs and give her a fresh oil and filter change. They always seem to love you for that ! I have always stuck with AC Delco supplies on GM engines and have had exellent results.

 

[Hoser85]

Re: SeaRay Seville 180 BR

I would also snatch off the flame arrestor and clean it with compressed air and choke cleaner. While it is off, push the throttle full forward and verify that the butterflies are actually making it to full vertical position.

 

[benmcclure]

Re: SeaRay Seville 180 BR

Thanks guys, definitely interesting.. I believe the faulty readings were from the ignition coil, it looks like the part where the wire that goes to the distributor connects to it was loose, inside was pretty beaten up. My guess is that the tachometer works by reading a voltage drop when there is a spark gap, and it may have been gapping inside that connector.

Anyway, replaced the distributor cap, rotor, ignition coil, threw new plugs in it. Anyway, its now running WOT at about 5600 RPM according to the tachometer I recently purchased and 4200 rpm according to the dash. I didn't want to hit above 4900 rpm so I backed off and let it sit at 4600 RPM, which was getting me 29mph, still seems like an awful lot of slip. Going to order a 21p SS prop and a new set of dash gauges and see if I can make better sense.

Also, everyone, remember to turn on the water when you go to test your engine after switching out a bunch of parts.. would have had her out to test yesterday, but completely burned up my impeller and spent this morning doing that job. I wondered why it was smoking so much after I switched out the ignition system.