omc 5.8 hard to get on plane

[jmarine225]

hello, well the saga continues. I have multiple things to go over hear so please pick and choose whatever information anyone may have. I have a 5.8 Omc Cobra in a 93 four winns Vista 245. I have to give it near full throttle to get up on plane. Full throttle on the boat is about 4500 RPM. Not sure if that is normal for the size of the boat or if I should be up at a lower rpm. Am I not doing something right to get up on plane? Next we get out on the lake, extremely choppy due to all the boats, jet skis, whatsoever and large waves are crashing into the sides and back of the boat. I had overheating problems in the past and I had it running for a long time around 160-185. It has a 160 thermostat in it. When I would should down though the temp would go up quite high. Not sure if that is normal due to the engine not running running and being able to cool the engine down. We get back to our slip and I notice we have some water in the bilge area, nothing major and no noticeable leaks. Could they water be due to the heavy waves hitting the sides of the boat? I really hope everything is okay here cuz I don't want to sink more money into this damn thing.

 

[airdvr1227]

Re: omc 5.8 hard to get on plane

Is this a new problem you're just noticing, or is this boat new to you? I can only tell you mine planes up at around 3000rpm but each is different. What outdrive?

You're going to have to be more specific. Are you saying that unless you run her at WOT (wide open) it won't plane?

I'm not experienced enough to address the temperature questions.

"Some water" is too vague. I always have some water in the bilge at the end of the day. Nothing alarming though. Is the amount of water a gallon or is it creeping up towards your powerplant.

 

[jmarine225]

Re: omc 5.8 hard to get on plane

new boat i purchased this year. Put a new drive on it, water pump, thermostat (160). Yeah probably around 3000 rpm it would take to get on plane. Maybe i'm not doing something right to get on plane. Can you tell me how to do it properly? And as far as the water, yeah probably a gallon or two.

 

[airdvr1227]

Re: omc 5.8 hard to get on plane

Others here know more than I, but I don't think you're doing anything wrong if it planes at 3000rpm. Mine's 23.5 feet and 4,000 lbs...yours is probably the same or a bit larger. Takes some power to get it on plane.

As for the water, I have a theory about older boats. I think the stress and torque of running throughout the day creates small leaks around the transom and through hull connections...and you have some water intrusion by the end of the day. Just a theory and I have nothing to back it up with.

I'd be much more concerned with the temp issue.

 

[dubs283]

Re: omc 5.8 hard to get on plane

when getting on plane, the drive should be trimmed all the way "in" or down

once on plane then trim the drive "out" or up and you will notice the change in how the boat rides in the water

bow up = drive up, bow down = drive down

also, if the boat is equipped with trim tabs, there are different setting for these

is the bottom of the hull dirty with marine growth?? this has a major affect on performance as well

 

[billiec]

Re: omc 5.8 hard to get on plane

as far as the water I would check the seal around the drain plug. Often just tightening the screws will put a stop to the problem.

 

[Powelling]

Re: omc 5.8 hard to get on plane

What prop do you have on? Might want to go to a lesser pitch

The prop on it might be more for top end speed. If that is the case then it will take more rpm to plane

 

[Gary H NC]

Re: omc 5.8 hard to get on plane

The engine has been run at the high end of the temp range. Did it do any damage?Who knows.
I would start with a compression and leakdown test.If that checks out then a full tune up.Plugs,wires,cap,rotor timing check,ect...Then fuel filters.

 

[mkast]

Re: omc 5.8 hard to get on plane

hello, well the saga continues. I have multiple things to go over hear so please pick and choose whatever information anyone may have. I have a 5.8 Omc Cobra in a 93 four winns Vista 245. I have to give it near full throttle to get up on plane. Full throttle on the boat is about 4500 RPM. Not sure if that is normal for the size of the boat or if I should be up at a lower rpm. Am I not doing something right to get up on plane? Next we get out on the lake, extremely choppy due to all the boats, jet skis, whatsoever and large waves are crashing into the sides and back of the boat. I had overheating problems in the past and I had it running for a long time around 160-185. It has a 160 thermostat in it. When I would should down though the temp would go up quite high. Not sure if that is normal due to the engine not running running and being able to cool the engine down. We get back to our slip and I notice we have some water in the bilge area, nothing major and no noticeable leaks. Could they water be due to the heavy waves hitting the sides of the boat? I really hope everything is okay here cuz I don't want to sink more money into this damn thing.

In a twenty-four foot boat, the engine will need all the torque it can produce to get the hull on plane. Going to a smaller pitch will raise the WOT rpm.
Try reading your post before submitting it, it's tough to figure out what you're trying to say.

 

[jmarine225]

Re: omc 5.8 hard to get on plane

yeah, not a problem with the plug as we were on the water for a while and I noticed the water in the bilge after the waves hit the boat and came over the boat. I'm thinking maybe water enter the thru hull fittings in the rear as one fitting is for a second bilge which is not there but the hose is.

Next, sorry bout my original post. I meant to say after running the boat for a while at normal temp I would shut it down and it seems the temp gauge rises. Is this normal due to the engine being hot and since its not running it isn't being cooled? I started it up again and the temp goes right down to normal.

Also I thought the engine is only supposed to be run trimmed all the way down as it places stress on the connections/joints if the engine is run raised up?

 

[mkast]

Re: omc 5.8 hard to get on plane

Also I thought the engine is only supposed to be run trimmed all the way down as it places stress on the connections/joints if the engine is run raised up?

The sterndrive is what moves up/out or down/in. Have you read an operator's manual?

 

[jmarine225]

Re: omc 5.8 hard to get on plane

Yes I have read the manual but on the forum is says only run the engine all the way down. I have trim tabs (and know how to use them) and then a button to either raise or lower the drive on the throttle. That is all I have. The owners manual doesn't say anything about it.

 

[jmarine225]

Re: omc 5.8 hard to get on plane

i guess my main question is about the overheat. After running your engine for a while at normal temperature is it normal for the temp to go up after shutting your engine down? I figured it was since the cooling water isn't circulating through an already hot engine.

 

[danond]

Re: omc 5.8 hard to get on plane

Couple things. You said it has a new drive. Did you keep the drive ratio the same as the drive it came with?

There is no expansion of anything when you're running that results in leaks. If there is, there's a problem. If you have water in the boat, either you took a wave or you have a leak that needs to be addressed. Next time you take it out let it sit at the dock for a few hours and see if it takes on water. If so, you have a new project.

The engine temp doesn't rise when the engine is turned off. The gauge is the only thing registering warmer when the boat sits. The engine can't generate any additional heat when it's off. It's just heating up the water that is no longer circulating.

When was the boat's last tune-up? Are the secondaries on the 4bbl carb opening?

Finally - if you plan on not spending a fair amount of money on your old boat, sell it. They cost to run. You can't avoid it!

 

[jmarine225]

Re: omc 5.8 hard to get on plane

Funny. I already spend a fair amount of money on the boat to get it to this position. We did take alot of waves in the water, some actually coming up the back of the boat. One problem I noticed is the unused hose in the bilge area connected to a thru hull fitting. I believe it is for a 2nd bilge pump. Any water that hits the side of the boat will flow right through that into the bilge.

I've also read alot of stuff on these forums. The rising water temp after the boat is shut down won't cause any steam which in turn would crack the block? Thought I read that somewhere on here.

 

[bruceb58]

Re: omc 5.8 hard to get on plane

After running your engine for a while at normal temperature is it normal for the temp to go up after shutting your engine down?

It is normal.