Is my boat allergic to water

[gcrouse]

ok i need help i am at my last draw here. ran my boat at the first of the season ran great planed out good ran great for 10 mins then its like i just cut the switch off and it hasnt ran right since. i have replaced plugs, wires points condenser, dist cap rotor, carb rebuilt, new filters, fuel pump checked, vent for tank checked still no change. when its hooked up on the muffs it runs great idles great great throttle responce revs up great, then i take it to the lake idles great i throw the throttle to it and at wot all i can get is 10mph and about 2800 rpm its like the boat is under a really hard bog and will not open up to full throttle. its getting very discouarging. i have a 88 four winns with a 3.0 4 cylinder in it with a rochester 2 barrel. any help would be greatly appricated cause im out of ideas. thanks

 

[Zamble]

Re: Is my boat allergic to water

I am far from an expert, but is it possible your prop is spun? I had a similiar problem, low speed, hi rpm. Mine was spun. Prop shop said it wasn't, lol. Got a new matching set for my twins and the problem was gone.

 

[SeanMcl]

Re: Is my boat allergic to water

i take it to the lake idles great i throw the throttle to it and at wot all i can get is 10mph and about 2800 rpm its like the boat is under a really hard bog and will not open up to full throttle

Possible restriction to the exhaust? If you have been over the ignition and and the fuel feed system, all you are left with is compression and exhaust.

"Flapper valves" sometimes break loose and get stuck in the intermediate housing, but I am unsure if your '88 has them. Does your manual show any?

 

[HT32BSX115]

Re: Is my boat allergic to water

at wot all i can get is 10mph and about 2800 rpm its like the boat is under a really hard bog and will not open up to full throttle.

Howdy,


If your engine is still "loaded" meaning it WON'T turn any more than 2800, I have a hard time believing the prop or (coupler for that matter) is "spun".


Those components will slowly get worse and eventually (in minutes) would act like the drive is in neutral.

have replaced plugs, wires points condenser, dist cap rotor, carb rebuilt, new filters, fuel pump checked, vent for tank checked still no change. when its hooked up on the muffs it runs great idles great great throttle responce revs up great,

Did you do this stuff BEFORE you took it out to the lake and discovered the "problem" or after?


If it did it after, you may have screwed up the timing, or have a bad (fouled) spark plug, wire or both.....(any pops or bangs?)

If it did it after running right for a while, you might have an obstruction in the exhaust, a carb problem(even though you rebuilt it) , or other obstruction to fuel flow like a failed fuel pump etc..... try using a different (portable) fuel tank.

 

[trihull59]

Re: Is my boat allergic to water

Before you throw any more money at it do a compression test its simple and easy

 

[j_k_bisson]

Re: Is my boat allergic to water

How much gas was in it over the winter. Also what kind of gas? DId you treat it before storing it. Sounds like possible phase separation of the gas if it is ethinol. Also as you ran it you shake it up and all the crap in the bottom of the tank get in the gas and possible plugging a filter or c arb jet is no filter. I would check the fuel system. Also sample the gas into a jar. See what you get.

 

[patrick53]

Re: Is my boat allergic to water

I am having the exact same problem...

Here is what I have done so far:

I have a 1989 Bayliner 2556 with an 240HP V8 OMC 305 and the Cobra outdrive. Over the winter I had a lot of work done on the boat including winterizing service, engine tune up and service, outdrive service, carb rebuilt, new starter. I took the boat out and after about 15 minutes of running at about 3/4 throttle the engine started to bog down. It ran very well up to this point, so I decided to bring it back to the marina and start the troubleshooting process.

I started by inspecting both of the fuel filters and the fuel pump, which showed no water in the inline filter and the little filter in the carb was totally clean, but I went ahead and replaced them anyway. Next (after reading some forums) I checked the vent line on the fuel tank, which was totally clear (some people had reported nests being built in them). I pulled the flame arrestor off and and ran the boat and it seems to be getting plenty of fuel. I did notice that in the secondary jets, one side was getting more fuel (a little) than the other, so I puled the carb off and sent it back to the guy who rebuilt it and had him look at it. He check it out and didn't find anything wrong and said a little more fuel on one side is not uncommon.

I took it out about a week later and same thing. Boat ran good for about 10-15 min then serious loss of power. At this point I had a mechanic come out and inspect. He found that the gaskets were bad between the exhaust manifold and risers, so we replaced them. He said that there could be water leaking into the manifold and could cause the problem. We also did a compression test and got good compression in all of the cylinders (spark plugs all looked good too). I am not seeing any increase in temp and verified that I am getting good water flow through the exchanger.

I can run for hours at lower RPM (about 1/4 throttle) with no problem, but I can't get the boat over 3000 RPM and it feels really sluggish past ~1/2 throttle. Also, once the boat is warm, if I back down to idle the engine dies, so I have to rev it up to about 1000 RPM. I am running out of ideas. I am thinking about replacing the carb, but that could is just a shot in the dark.

Someone mentioned to try holding the choke open as it may be stuck, so I am going to try that too. The exhaust flappers sound reasonable, but is there any reason why that would have a more profound effect as the engine warms up?

 

[duane.mosley]

Re: Is my boat allergic to water

@patrick53... i had the same problem on an 88 omc 305 cobra.i could put around all day but couldn't get it really going, and it was the secondaries not opening properly. we opened the engine bay and used a stick to assist the secondaries to open and things were great. adjusted the tension on the secondaries and things were fine. this might help your case. did mine.

as for the idle issues. i had the same problem and we think the bowls on the carb were bent. assuming that you have a q-jet. good luck. i sold mine(regretfully) so we didn't get to have a final conclusion on the idle issues.