OMC speed question

[idesign]

Guys i have 17.5ft Doral bowridder.It has OMC 3 liter 4 cylinder inboard & OMC Cobra outdrive.It is new used boat i bought and have question about speed.I tested that day in lake Ontario and it reached max 30mph.I sounded little less with this big engine inside.I have read people going 40 mph with small like 80hp outboard.so can any1 tell me if there is anything wrong or it is the normal speed with this type of motor.thx

 

[flawet]

Re: OMC speed question

Take note of your tach/rpm. Are you at the high end of the range at WOFT? If not you may have too large of a prop for speed. Lots of those confugurations are set up for multiple passengers and therefore a larger prop to handle the weight.

 

[steelespike]

Re: OMC speed question

Under ideal conditions it would run about 40.Probably with a 19 or 21 " pitch prop.If it has less pitch as for skiing it would be somewhat slower.On board speedos are allways inaccurate. not unusual to be 5 mph off + or -.Only way to be sure of speed is with a gps.Normal max rpm is about 4400 to 4600.

 

[jerryjerry05]

Re: OMC speed question

The speedo on the boat could be off.Get a GPS and check the speed with that.You should be closer to 40mph on a 17ft boat with the trim set right and the motor running good. If only doing 30 on GPS come back with the tach reading at WOT,and the prop size.J

 

[chiefalen]

Re: OMC speed question

Tuned right?

Bottom clean?

No extra weight like water under the floor stringers water logged?

What prop on it now?

That boat should do better than 40.

What is the idle on the water with boat in gear?

What is the compression?

Hows the plugs look?

 

[idesign]

Re: OMC speed question

Tuned right?

Bottom clean?

No extra weight like water under the floor stringers water logged?

What prop on it now?

That boat should do better than 40.

What is the idle on the water with boat in gear?

What is the compression?

Hows the plugs look?

Thx to you & all who replied.I will note everything i when i go to test drive boat this Weekend.I will give update.
BTW,how do i check compression & how do i check "idle on the water with boat in gear",Also about "What prop on it now?" should i measure the length/width.I will also take some pic/vid and will post here.

This is my first this type of boat so dont really no more about it.thx for help guys.i appreciated.

 

[jerryjerry05]

Re: OMC speed question

The prop should have #s printed on it somewhere.
For compression you will need a guage(auto zone or any chain store) should have. Take the plugs out and open the throttle all the way then hook up tester and turn motor over.The comp should be within 5-10# of each other.
Say 3 of the cylinders have 120# each then the 4th has 70# then you know there is something wroing.. Get back with the results.Jerry

 

[idesign]

Re: OMC speed question

Guys i got out this Sunday and manged to use my boat again.Here is the info requested
At full speed the rpm is about 3600.Boat was going about 29mph with 3 adult inboard.see pic attached.




As per propeller.there is something written.IT says "13x19" "390896" "68" "D7"
this is all written on propeller.I also have extra propeller came with boat.I saw it and it looks like it is little bigger then currently i have on the boat.see pic attached.

So can1 tell me if propeller is slowing the speed.
I asked the guy i bought the boat about speed and he said the propeller is designed for fishing not cruising.not sure if he was right.let me know.thank you

Also the speed gauge on boat shows upto 60mph.So i think the boat should go more then 30mph.pls help me out.

 

[Gary H NC]

Re: OMC speed question

Thats a 19 pitch prop.
You are missing about 800-1000 rpms at top speed. Something is slowing you down.
First thing would be to do a complete tune up on the engine.
Points,plugs,wires,timing and dwell set.
How does it idle? Is it smooth?

Fuel filters been replaced?

 

[idesign]

Re: OMC speed question

Thats a 19 pitch prop.
You are missing about 800-1000 rpms at top speed. Something is slowing you down.
First thing would be to do a complete tune up on the engine.
Points,plugs,wires,timing and dwell set.
How does it idle? Is it smooth?

Fuel filters been replaced?

idle looks ok.i start the engine and let it run few minutes.didnt check rpm but looked ok to me.i will try to get idel rpm if i go this weekend.
as per fuel filter,i dont think it is replaced.BTW,do u know where it is.

Also forgot to mention,when i was trolling at 2.5mph speed i noticed the oil gauge showing low& later also i checked it still shows low.i talked with owner yesterday and he said it is like that all time.

As per engine tune up,only Condenser was changed and setuped when i bought the boat.

pls let me know what to do.thx

let me know.

 

[Gary H NC]

Re: OMC speed question

There is a fuel filter at the carb where the fuel line screws in.Also there may be one before the fuel pump in the engine compartment.Thats a water separator filter that looks like an oil filter.(it may never had one installed)

It sounds like the previous owner just replaced the condenser? Was that just to get it to run and why?

How long has it been since it was REALLY tuned up?

Thats points,condenser,rotor,cap,wires,plugs...timing set and dwell set?
At this point a compression test would be my first step.

 

[chiefalen]

Re: OMC speed question

Please do a compression test first thing.

Get the gauge and remove one plug at a time and screw the gauge into the block, crank the motor till it turns over at least 4 times.Record the number and what plug it is.

Remove the coil wire from the distributer first please.

So it don't start.

And post the results please, before you do anything else.

Thank you.

 

[idesign]

Re: OMC speed question

Please do a compression test first thing.

Get the gauge and remove one plug at a time and screw the gauge into the block, crank the motor till it turns over at least 4 times.Record the number and what plug it is.

Remove the coil wire from the distributer first please.

So it don't start.

And post the results please, before you do anything else.

Thank you.

thank you for info.I will try to get test tomorrow morning and i will post result here.

Just making sure,I am sure i can do this test at home without taking boat to lake as i will not be starting motor just cranking it.can some1 confirm.thx

 

[chiefalen]

Re: OMC speed question

You do not want to start the boat, can be done anywhere.

Remove the coil wire from the dizzy please. Center wire.

 

[idesign]

Re: OMC speed question

Guys i got the compression test done this morning.Here is the result.I am not sure if i did right,Some plugs i tired 2 times and got same #.here is pic attached.please let me know the next step.thx

 

[drrm123]

Re: OMC speed question

compression is kinda low on #4 could be bad rings you can squirt some oil in that cylinder to see if pressure comes up if it does the rings are bad, if not the valves may have a problem, compression should be 20-30 psi within each other. #3 is kinda high could be carbon build up. sure someone else should get back to you today with more info. if you have equipment to do leakdown test it can give you more info.

 

[chiefalen]

Re: OMC speed question

I have seen worse numbers.

There are 2 ways you can go from here.

I'll give you the way i would go if it were my boat.

I would pull the # 4 spark plug and shoot some wd 40 in the hole real good, and re-do the compression check. Maybe shoot all the plug holes.

Post the results.

Could be the valves and the seats might need to be polished a bit, maybe.

You could do it yourself for nothing.

First let's see what the compression test shows.

But this is not the reason your not getting close to a 1000 rpm's you should be getting.

What does the oil look like.

If like posted bye other great mechanical minds here, a tune up is in order.

A full tune up.

I asked about the oil cause you probably don't know when it was changed.

It has the correct amount not over filled.

When you do go to run it again, after you did your tune up, can you borrow a shop tach and bring a gps and give us accurate numbers.

2 people on board and maybe a half tank of gas. And prop size used.

Good luck.

 

[idesign]

Re: OMC speed question

I have seen worse numbers.

There are 2 ways you can go from here.

I'll give you the way i would go if it were my boat.

I would pull the # 4 spark plug and shoot some wd 40 in the hole real good, and re-do the compression check. Maybe shoot all the plug holes.

Post the results.

Could be the valves and the seats might need to be polished a bit, maybe.

You could do it yourself for nothing.

First let's see what the compression test shows.

But this is not the reason your not getting close to a 1000 rpm's you should be getting.

What does the oil look like.

If like posted bye other great mechanical minds here, a tune up is in order.

A full tune up.

I asked about the oil cause you probably don't know when it was changed.

It has the correct amount not over filled.

When you do go to run it again, after you did your tune up, can you borrow a shop tach and bring a gps and give us accurate numbers.

2 people on board and maybe a half tank of gas. And prop size used.

Good luck.

thx for reply.
I will try ur wd-40 option tomorrow and will post result.
as per oil,i checked it this morning and it looks black.need to change it but don't know how.if u can tell me it would be great.also what type of oil does it take.can i get that oil in local part store .
pls let me know.thx

 

[idesign]

Re: OMC speed question

Other then oil change what else is needed for full tune up.If some1 can tell me the type of oil it takes it would be great.
Note: Distributor&Condenser is new.
Also can i get the spark plug & oil filter in "Canadian Tire" or any local park store.

If you can list the things required for tune up it would be great.

let me know.thx for helping me guys

 

[Gary H NC]

Re: OMC speed question

There should be threads on the dipstick tube that looks like a garden hose will screw on.Thats the best way to pump the oil out.
Use SAE 30 weight oil. Rotella oil sold in truck stops and auto parts stores is good.Not 10w-30 just straight 30 weight.
Spark plugs are probably AC MR43T or should be,
You need a Marine distributer cap.
Plug wires can be matched at the auto parts store.

You can use a drill pump and attach a piece of garden hose to it,
One like this,
http://www.sears.com/shc/s/p_10153_...& Pumps&psid=FROOGLE01&sid=IDx20070921x00003a

Warm the engine up first then suck the oil out.

All the parts you need for tune ups...
http://bpi.ebasicpower.com/pc/SMI98104___/OMC9K/Ignition+Wire+Set+Delco+OMC+EST+4+Cylinder