Won't reach top speed

[dtlaine]

Just for the heck of it, I took the boat out on Sat w/ no intention of riding. I thought I'd just go play around. Much to my surprise, the boat would only reach about 4000 RPM's or 35 MPH. With the throttle wide open, it would reach make a loud knocking sound, and it sounded like it was really struggling. The weird thing is that it went from 0-30 just like it always does. I took it out of gear, and it would rev to 5000+ with no load, but if I went from idle to WOT in neutral, it would knock at the higher RPM's. I spent a ton of time this weekend entertaining at idle speeds going through the canals around here, and it ran fine doing that.

The boat is a 2000 OB with the 310 HP carbureted 350. I didn't use it much in Sept, so I think some of the fuel in there was a least 6 weeks old. I'm thinking that may be the issue. I put some StaBil in it, so the fuel won't get any worse. Does anyone have any other ideas?

Thanks in advance.

[smokedog2]

I think perfectpass can cut a little off the top end. How long have you had the boat? I don't think I ever hit 5000 on the water 4100- 4500 is top end I think, is the speedometer calibrated?

[Engine Nut]

Just for the heck of it, I took the boat out on Sat w/ no intention of riding. I thought I'd just go play around. Much to my surprise, the boat would only reach about 4000 RPM's or 35 MPH. With the throttle wide open, it would reach make a loud knocking sound, and it sounded like it was really struggling. The weird thing is that it went from 0-30 just like it always does. I took it out of gear, and it would rev to 5000+ with no load, but if I went from idle to WOT in neutral, it would knock at the higher RPM's. I spent a ton of time this weekend entertaining at idle speeds going through the canals around here, and it ran fine doing that.

The boat is a 2000 OB with the 310 HP carbureted 350. I didn't use it much in Sept, so I think some of the fuel in there was a least 6 weeks old. I'm thinking that may be the issue. I put some StaBil in it, so the fuel won't get any worse. Does anyone have any other ideas?

Thanks in advance.

A carbureted engine should be able to turn at least 4400 RPM and should be propped not to exceed 4800 RPM at wide open throttle with a normal load in the boat. If it will not turn at least 4400 the boat may be overpropped or have a problem. If it turns over 4800, it is under-propped. Either condition will be detrimental to the life of the engine and may lead to a catestrophic failure that is not covered under the Indmar warranty. In other words, you best get it checked out!

Engine Nut

[dtlaine]

I don't think it's a prop issue. It is simply not running like it usually does. The speedos are calibrated. Maybe it doesn't normally turn 5000 RPM's, but it definitely normally turns more than 4000. I've run it at WOT for a while across the lake, and it normally doesn't make the popping or knocking noises it was on Saturday.

It does not have Perfect Pass, either. It just felt like it couldn't pull the higher RPM's under load. I'll give it another run tomorrow, and I'll see how it does. Luckily, I live on the lake, so it's no big deal to take it out for a run or two. By the time I get through the canals, it's running at 160 degrees, and it's ready to pull.

Thanks for the responses. If anyone else thinks of anything, let me know.

[qb12]

when was the fuel filter replaced.

on my 05 supra ssv 22, boat ran great till about 3500 rpm's. if i went over that it heistated and ran really rough.

took the fuel filter out and it full of junk.

replaced and ran like a champ.

[spyder]

when was the fuel filter replaced.

on my 05 supra ssv 22, boat ran great till about 3500 rpm's. if i went over that it heistated and ran really rough.

took the fuel filter out and it full of junk.

replaced and ran like a champ.

I am currently in the same situation.. with an 06.. how can an 06 have a clogged fuel filter already?

[qb12]

my 325 hp ran great until a 4th of july trip to the lake. filled up with gas on the water and the problems started then.

it is a very simple check.

[dtlaine]

Mine was replaced this summer, but I'll definitely check it out. What do most people do about the fuel/water separater? I thought I've read that some people bypass it. I'd be concerned to do that unless someone with an awful lot of credibility advised me. My boat sits at my dock, and even though it's usually covered, I can't help but think maybe water is getting in somehow. I mean, air has to get it to replace the fuel as it's burned, so there's an inlet somewhere.

Thanks again,

Don Laine

[Buttafewcoe]

I believe the vent is in the gas cap.
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