I can run faster than my boat on water!!!

[Desertboater]

I ran my boat yesterday at the lake and I swear I can run faster.

It's a 77 75hp Johnson and clocked it with my gps at 25mph at wot!! I'm new to boating but I know that engine can go faster than that. Right???

Did a carb kit on it recently, starts fine, idles good but when I open it up it planes but top speed is 25mph. Ran it for a while and it just wouldn't go any faster. Then after idleing for about 8-10 minutes while we rigged up our fishing rods I decided to open it up again and it just bogged down bad woudn't plane.

I'm running my plugs at .030 manual says .040 will that make a difference? Could I be fouling the plugs?

Also I checked all the wiring today and noticed a really bad corroded wire on my rectifier & lead assy. Could that be whats causing the poor performance on the boat?

Sorry for the machine gun questioning and thanks in advance for the help.

 

[david_r]

Re: I can run faster than my boat on water!!!

i thought you could run on water, lol

what kind of boat?

what is the max hp for the boat?....... it should have a tag on/in it somewhere.

how much total weight are you adding to it?

what size prop?

do you have a tach?..... max rpms?

you need to run champion plugs and gap them at .040

any corrosion on any other wire connections?

 

[Desertboater]

Re: I can run faster than my boat on water!!!

it's a 15ft 86 bayliner

I know I read somewhere that max hp on this rig is 50hp? Does that sound right? I know the previous owner said he changed motor from it's original.

It was just my girlfriend 120lbs and myself 195lbs and a six pack. max pounds on the boat tag says 600lb and for sure we were way under.

prop is 13 3/4 X 15

i dont have a tach and the manual says full power is from 5200-5800 rpm and best performance is on the upper end of 5200-5800.

plugs are champion

no other corroded wires as far as I can see...

just did a compression test and it looks like this: 100 100 95

 

[Huron Angler]

Re: I can run faster than my boat on water!!!

What year is the boat and was it stored outdoors ever? You may have engine issues(check compression...get a tach) OR you may have rotten plywood issues.

Or possibly both. If you can identify any issues with wetness in the transom or deck then folks on this site can let you know how to fix it.

Good luck and welcome to iboats desert boater

 

[Desertboater]

Re: I can run faster than my boat on water!!!

I believe the boat was stored outside but it seems pretty solid.. I know I have a soft spot on the deck towards the back of the boat. It's maybe 2ft x 1ft area that is soft but the rest of the floor is solid and it doesn't take in water.

How do you detemine rpms with a tach?? Sorry i know thats bad but im learning as a go...

compression is 100 100 95

 

[david_r]

Re: I can run faster than my boat on water!!!

you will not be able to determine the rpms without a tach....... a tach will run you about $60, but you need to make sure your rectifier isnt burned up. you can find the test by joe reeves in the frequently asked questions forum.

if you have a soft spot that is bad. my first fiberglass boat had a soft spot........ the more i dug the more rotten and water soaked foam i found. on the brown boat in my avatar i pulled out 6 outdoor leaf trash bags of water soaked foam... i weighed the bags and got almost #300 of wood and foam out of it....... you can find out how to tell about water intrusion in the boat repair and restoration forum.

if your boat is rated for a 50 and you have a 75 you should be able to scoot across the water........ how fst i cant tell you, but a 15 pitch prop sounds under-proped for a lighter boat.

without knowing your rpms it is hard to determine which prop you need....... and if that is the max mph you will achieve.

each boat manufacturer has different designs so each one will perform different.

does the eng stall or cut out or sound like its bogging?

bad fuel or water in the fuel will also effect the performance.

you can find the approximate weight of your boat on n.a.d.a.com and that may help us.

 

[F_R]

Re: I can run faster than my boat on water!!!

Your first order of business should be to find out if the motor is running on all three cylinders. Remove and ground each spark plug wire at a time, and see how much your speed changes each time. I'm betting it won't change at all with one of them grounded. That one is not firing when connected.

Once you find which one is just going along for the ride, the next order of business is to find out why. Can be the carburetor associated with that cylinder, or no/weak spark on that cylinder, a bad spark plug, or water getting into the cylinder. Not to mention a blown piston. Yes, it CAN have compression with a blown piston.

 

[Desertboater]

Re: I can run faster than my boat on water!!!

So would a bad rectifier cause one of the cylinders not to fire properly? The red wire on the rectifier is bad all the way thru.

I just don't think it's a water soaked issue because the engine would perform the same all the time. It wouldn't bogg down after ideling for 8-10 minutes.

I failed to mention that I pulled the plugs (new) and could see that they were fouled.

Fuel is good, I agree with you David I should be scooting with that 75hp Stinger..

Once the motor bogged on me I changed to new plugs but I opened them a bit more than .030. It started right up but when I opened it up it was still bogging for about 45 seconds and all of a sudden the motor reved up and took off again, plaining but top speed was again at 25mph. Took those plugs off and they looked alot better than the first set..


I don't know guys...

 

[kenmyfam]

Re: I can run faster than my boat on water!!!

Basic stuff to begin with.
Compression.
Spark.
Fuel delivery.
Spark plug condition (is one different from the others).
RPM at WOT (in the water only and not on the muffs).
You have found one bad wire already. How many more are there ?? and where??

 

[Knightgang]

Re: I can run faster than my boat on water!!!

Without RPM numbers, it is hard to say, but it sounds like part of the issue is you are under propped. I would also get that rectifier fixed ASAP.

 

[jeff_smith_0423]

Re: I can run faster than my boat on water!!!

A healthy looper should be compressing 120psi - so double check your compression with another gauge. I second the underpropping. Seems like you should be swinging a bigger wheel with that motor on that rig. Also - mid 80's Bayliners are notorious for rot and water logging. Check your flotation foam and make sure you're not dragging 500 lbs of water weight with you.

 

[Desertboater]

Re: I can run faster than my boat on water!!!

Well I just tore up the floor where I had the soft spot in back of the boat and i remove all the rotted plywood from the floor and checked the foam and it looks good. Thank GOD!!

Well on my way to Home Depot for supplies to replace that soft spot that I just removed.

I'll go ahead and order a new rectifier see if that makes any difference. 49.99 plus shipping, not bad. Hopefully that will make the difference.

kenmyfam after i put in the second set of plugs with the gap a little wider than .030, first plug looked a bit too black while the second and third looked good. Hmm.. What do you make of that??

 

[JB]

Re: I can run faster than my boat on water!!!

How long have you had this boat/motor? Has it ever performed differently for you?

 

[a70eliminator]

Re: I can run faster than my boat on water!!!

doublepost

 

[a70eliminator]

Re: I can run faster than my boat on water!!!

If it makes you feel any better my 16' MFG with an 80HP with just me a flat lake and a tailwind only gets up to about 32MPH. After 10mins of idling and you open the throttle and get bog than the engine is not in good tune.

 

[Desertboater]

Re: I can run faster than my boat on water!!!

I just bought this boat 2 months ago and no it hasn't performed for me any better. It's been doing this since day one. Start off ok then idle for a little while and bogs down. I've done a carb kit, changed plugs, checked and replaced some water pump parts, checked impeller, changed gear oil, now the rectifier.

It's a work in progress but I'm confident that with everyone's help we'll get this thing going good.

 

[bktheking]

Re: I can run faster than my boat on water!!!

25 mph with a 75 on a 15ft boat is crap, I agree, we get 23mph out of a 64 big twin 40 on a 14ft runabout, did you do all checks as suggested?

 

[Desertboater]

Re: I can run faster than my boat on water!!!

I checked compression and it's 100 100 95 and I did that without the engine being warm. I dont know if that makes a difference.

I need to check spark but I am a little confused as to how to do it but I'm sure I'll read here somewhere on how to do it.

What about timing guys? Would that cause the engine to perform badly as it has?

Could a bad rectifier cause the poor performance? It is part of the ingintion components right?

Anyway guys let do some research and find out what I need to check spark and I will come back and post.

Thanks guys..

 

[jeff_smith_0423]

Re: I can run faster than my boat on water!!!

If the timing is not advancing, you will not get full performance.

I don't think your rectifier is the problem - even if it's bad it should still run, just not charge the battery. However, if it's shorting something out elsewhere, maybe.

Still think you need to check your compression with another gauge. Doesn't matter, hot, cold, just recheck with a different gauge.

All you need to check spark underway is a helper to drive the boat and an inductive timing light. Connect to each spark plug wire while underway and watch the light.

 

[outlaw241]

Re: I can run faster than my boat on water!!!

make sure your nozzel washers are in good shape,if they are not it will suck air above the float level in the carb's at wot.i had same symptons an that was the problem,hope this helps