New to the forum, having a few problems

[carhopper]

Hello everybody, I'm the proud owner of a 1993 17.5' Caravelle bow rider with a 3.0L OMC Cobra. The boat had 3 or 4 electrical problems which I was able to fix no problem. It had some loose grounds, bad fuel gauge, and I put in an automatic bilge pump switch. Now for the problems I can't fix or diagnose.

1. The boat seems underpowered. I can hit about 38mph by myself with it trimmed out at 4,800 RPM. According to the sticker on the engine, this is max rpm. I'm thinking possibly the prop was changed for a hole shot since it has a raptor stainless, but I don't know the size or pitch. Just looking for an opinion.

2. The engine has developed a rattle, especially when cold. I can't hear it when under power, but when I'm at idle it taps at about 4 times a second. It's hard to tell where it's coming from. Is this common? Oil is new and full. Engine develops about 25-30 psi at idle, 40-60 under load.

 

[chiefalen]

Re: New to the forum, having a few problems

Welcome. When was the last tune up done? Reason im asking is: it would rule out alot of things, like timeing, dwell, plugs being foul, points good if you have them for example.

Is the bottom clean?

Could the foam be wet? In the floor, would add a ton of weight.

At w.o.t you should be at 4800 rpm did you gps the speed to make sure the speedo on the boat is right?

Is the cables set right? When you give it full power is the carb opening all the way?

Good luck

 

[carhopper]

Re: New to the forum, having a few problems

The boat was tuned up by the previous owner before I bought it. It has new plugs, distributor, oil change, etc, and a rebuilt carburetor. I haven't verified anything myself.

The boat is stored out of water and the bottom is clean.

How do I check for wet foam?

Yes, I used a GPS too and it matched. I can actually get over 5,000 just slightly with a lot of trim, but I backed it down so I wouldn't damage the engine. This must point to the prop.

Full throttle is full deflection of the throttle plate.

 

[chiefalen]

Re: New to the forum, having a few problems

You should never go over 4800 rpm. IF you can get 5000 than your under proped meaning you should be 2 dagrees higher to lower rpm could be your problem.

You have any openings in the floor you can stick a mirror in to see the foam? I don't want you to cut holes in the floor but....

You could have the boat weighed if you know what ir should weigh with trailer.

You should be around 45 mph.

Any marinas there let you rent or borrow a few props?

My guess get a 19 to start for sure than try a 21- 23. Alot of marinas will let you try them if for sure your gonna buy one.

good luck let us know how u made out

 

[danond]

Re: New to the forum, having a few problems

Most props I've seen have the size and pitch indicated inside the prop where the exhaust exits.

Did you put the auto bilge switch in because it takes on water? If so, your ticking could be shot u-joints or gimbal bearing.

 

[Dakota47]

Re: New to the forum, having a few problems

I would not run that old 3.0 for long @ 4800 rpms or you will be hearing more than a rattle

 

[chiefalen]

Re: New to the forum, having a few problems

I should have added i always run at 1000 rpm below my w.o.t . Mine is 42-4600 I run at 3500.

 

[carhopper]

Re: New to the forum, having a few problems

Thanks for all of the great replies, now I'm a little worried. I may have damaged the engine already by over revving because the noise wasn't there initially.

Yes, I'm taking on water about a drip every couple of seconds. I tightened up the transom bolts but it didn't fix the problem.

 

[texsun]

Re: New to the forum, having a few problems

The rattle you hear may be the mechanical fuel pump. My 3.0 Volvo has a mechanical F/P and it's always audible at idle.

Also...if your getting 4800RPM's and 38 MPH that's probably as good as it gets. Does the engine start, idle, and accelerate well? If so that may be tops for your particular set up. I have a 96 LArson 174 and it runs about like yours. I very seldom run it over 4000 though.

Enjoy!