top speed issue

[poverty stricken II]

I am asking this for a friend who has 1988 4cyl 170 hp merc i/o.

The problem is that his boat as it gets up on a plane and winding up to full speed, the engine starts to chug like it is starving for fuel. The engine runs fine at idle. He had the fuel filters replaced (one looked like it had been dented by vaccumm pressure). This did not do anything to help in the problem. The marina he has it at is giving him the old Hey lets try this $300 idea, oh that didn't work lets try this $300 idea. If someone else has had this problem let me know and I will relay the information, to have him give that a try. I can not get to the boat to do my own trouble shooting, but from what he is telling me sounds like a fuel issue.

Is there a screen on the pump in the tank?

[ray koziatek]

there is a little one way check valve at the fuel tank ((first outside connection)..might be some crap in that ...ya could try to remove fuel line near or in engine compartment ,put in the barbs of one of those squeeze primer bulbs clamp till firm and squeeze it should squirt out about 2 oz each pump and refill pretty fast ,aslo on the outgoing end put about a 2 ft piece of clear tubing and direct into clear jar so ya can get a good look at fuel for dirt and water. I guess as a back yard mech,the next step might be a carb rebuild kit pretty cheep and easy to do BUT FIRST I WOULD CALL HANK (L&M) for his advise , could be centrifrical weights in distributar are stuck for timing advance,internal port or passage in carb pluged,restriction in exhaust,(little waterbackflow thingy stuck or broke and jammed in there., without tinckering with it my self those are just a couple things id look for.

[woody 184]

PS how does the boat run when it is hot... Does it still idle nice or does it stall even after a couple hours of running... Just wondering I had a similiar issue with my old Penn yan and i found the coil was bad... Problem was it presented like it was a fuel issue and I change the fuel filters several times on the rochester carb and the inline marine filter to no avail.... Dale

[HPORT]

99% of all fuel problems are electrical....Lucas

If you think the filter collapsed from the fuel pump pulling on it, you could very well have a fuel restriction before the filter?

When it's spiting and sputtering, whack the fuel bowl on the carburetor. Just make sure you are well balanced when you do it, if its a dirt in the bowl and you knock it loose, the boat will take off. ( been there)

If not fuel, see first statement.

John

[ray koziatek]

yup 1 good wack with a 12 lb sledge should do it..i would guess your needle valve was a tad laqured up and wasnt droppin out for proper fillin and your tap freed that up ..some area if the carb are very thin walled so id save the old hammer trick for tired brushes on a starter of alternator. like i said if all else fails give ol Hanky a call or Mark and the owner at Swartout marine in hammondsport are top notch, If I really hated you id recommend a place in campbell,or the west side of seneca channel..suppose i could look at it if it ant too far from my driveway.

[GAMBLER]

Is it starving for fuel or a plugs, distributer, coil or spark plug wire problem? All things to check. If your distributer has corrosion, it can make your engine do funny things. I got a bad tank of gas 4 seasons ago and had carb issues. Mine would run really rough at high speeds. It seemed like it was starving for fuel. Were the filters full of crap?

[mschott]

I had a similar issue with my little boat -had a 40 hp o/b -would run great up to almost 1/2 throttle anything after that the motor would bog out .i changed all filters cleaned gas tank new gas line you name it .Nothing helped last ditch effort i changed the spark plugs (4) runs like a top now .

[dcso]

i had a similar problem, but mine was that the alchohol in the fuel over time had turned the suppy line to almost sponge rubber, the hose and was collapsing on itself as the pump called for fuel after I replaced the fuel line I had no problems! but do check the the one way valve as Ray said. look for the simple things first. I had a 110 jonhson VRO that gave me me fits. If nothing else take the suggestions from this site, I took that VRO to a place just below Vest NY ( no no name) and it cost cost me $800 to fix nothing. I had to figure it out on on my own and the advice from ths site. Hank's advise is second to none.

Ted

[poverty stricken II]

Thanks for all the replies. The boat idle fine at all times however it chugged like it was starving for fuel when underway and picked its own time to start chucking (meaning 1/2 throttle to full throttle). It was a Ball Valve in the carb.

He was only getting gas from the marina for the last 3 years and didn't have a water/fuel separator.

The marina that was working (remove and replace and charging high prices troubleshooting) on his boat near sandy pond area, told him that boats are having fuel related issues because of the ethonal mixture in today's fuel. anyone heard of this? I told him it was another way to get him to buy the additives and my boat has never had a problem.

Thanks again you guys are great.

Tim

[ReelPower]

Start simple and check all aspects of fuel delivery, as fuel starvation is the most logical choice. A carb issue would probably affect the idle.

I double the advice to examine the check-valve at the fuel tank outlet. Sounds like your buddy has examined other possible fuel flow issues. This is an often-overlooked source of fuel starvation. A little crap can wedge in there and prevent the check ball from opening properly.

I had the same problem...it was the check valve. Simple and cheap fix. Vroooom!

[ray koziatek]

Psst: (reelpower) it was a ball valve in the carb.(read post)

Maybe the oll 12 lb sledge would of got it going...

Ive been running reg gas sence it was introduced in the pumps without a problem .Much has been discussed here over the years about it ..And if everything is good just run it as it is ..(no add.)...........Biggest concern is with fiberglass tanks being dissolved or attacked by the new stuff,older fuel lines , and the "non typical " gas lines (older or cheap) used on some outboard boats ,the quick dissconnect types ,seems to be of a lesser grade and little chunkies will find their way to the "carb jets" usually the High speed jets. At seasons end i would consider a good rebuild on the carb and proper ultrasonic cleaning if he didnt do it allready..some over the shelf cleaners will "attack" the factory coating in the carb soooo make shure ya get a book ,or a good mechanic to do the job....

[ReelPower]

Oh that post! Thanks Ray. Never heard of an ultrasonic carb cleaning before...sounds cool.

[Tim Bromund]

Thanks for all the replies. The boat idle fine at all times however it chugged like it was starving for fuel when underway and picked its own time to start chucking (meaning 1/2 throttle to full throttle). It was a Ball Valve in the carb.

He was only getting gas from the marina for the last 3 years and didn't have a water/fuel separator.

The marina that was working (remove and replace and charging high prices troubleshooting) on his boat near sandy pond area, told him that boats are having fuel related issues because of the ethonal mixture in today's fuel. anyone heard of this? I told him it was another way to get him to buy the additives and my boat has never had a problem.

Thanks again you guys are great.

Tim

No, ethanol is a real issue. Here's some info from the Boat US Website on it and how it affects boaters:

http://www.boatus.com/seaworthy/ethanol.asp

Tim

[Knotlost]

I had a very simluar issue, believe it or not a huge bumble bee got into the tank and was blocking the intake. I would examin the hoses, then the check valve at the tank like an early poster stated, then you need to see if something got in the tank, a vacumed filter is not to be ignored...