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Bogging down at high RPM's (Mercruiser 4.3L/LX 205hp 262CID)

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bajaboater

New member
I have a 1989 Baja Islander 190 with a Mercruiser 4.3L/LX 205hp motor. The boat runs great at idle and well enough to get around the lake, however when I start opening up the throttle it will start to bog down on me and if I don't throttle down it will misfire and eventually stall on me. At first I thought it was just dirt in the fuel or maybe build up in the carb. I ran a bottle of Sea Foam along with 93 octane and it ran great all day, no bogging down while throttling up. Took it out a week later and back to same problem. So now I'm thinking it's something mechanically. The flame arrestor was rather dirty so I cleaned it up, however one of the hoses are lose. I don't know what problems that could cause, but I'm assuming something. The carb looks clean after taking the flame arrestor off so I don't think it's the carb. So now I'm thinking somewhere along the fuel system is not working properly. This motor does not have a fuel filter or seperator in it (maybe it does, but I looked everywhere and I don't see it). Could it be the carb fuel inlet filter causing the problems? If not, what else could I look into.

PS I'm a first time boat owner so I don't know my way around them real well yet.

Thanks
 
bajaboater said:
I have a 1989 Baja Islander 190 with a Mercruiser 4.3L/LX 205hp motor..... This motor does not have a fuel filter or seperator in it (maybe it does, but I looked everywhere and I don't see it). Could it be the carb fuel inlet filter causing the problems? If not, what else could I look into.

Thanks
Click to expand...

A fuel filter filter/seperator will be somewhere between the fuel pump inlet and the fuel tank. There are two types. Spin ons that look just like an oil filter and two part ones that have a water drain bowl (should be metal for this type engine, not plastic) stacked under a filter element. The whole thing is on a spin on style mount. There are also larger ones that are not spin ons but not likely on this small an engine.

Re: carb inlet filter. If you've never inspected/cleaned it, now is the time. I caution you strongly to only use the correct size quality open end wrenches on this, not pliers or vise grips. Loosten/remove, fuel line fitting, then unscrew the filter from the carb.

If you only have the carb inlet and not a filter separator now is the time to add one. I'd use the two piece one with a drainable water separator bowl. make sure you locate it where you can change the filter easily and drain the bowl. I should remind you that only metal bowls are USCG (and insurance company) legal on your type installation. Based on the age of your boat, I'd replace all hose style fuel lines from the tank back to the engine with current production marine approved ethanol proof lines if they are older than about 8 years, i.e., pre ethanol era. The linings in pre-ethanol era fuel lines are solvent, i.e. melt and end up in your carb bypassing even the best filters.
 
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You Have a fuel problem start by running from a gas can thus by passing tank then run from can on either side of filter see where it runs. Also crank it with fuel disconnected from carb to check that pump is pumping.
 
rl65028 said:
Also crank it with fuel disconnected from carb to check that pump is pumping.
Click to expand...

The only safe way to do this is to connect a fuel resistant hose to the fuel pump and then put the other end all the way down into the bottom of an empty 5 gal jerry can (to contain vapors). Otherwise you will dump fuel into the bilge.


BTW... I looked it up and your engine should have a mechanical fuel pump with a built in filter element (no water separator) mounted on the top of the pump itself in the "dome". These days, I'd still install a spinon filter/separator before the fuel pump.
Replace the existing filter element as a backup... you should never have to replace it.
 
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Got the carb inlet filter out. It was a mess, full of sand, old paper filter. The small gasket was basically non existent. Also, you are correct about the fuel filter. Took apart the fuel pump and found the filter with a rubber gasket. The filter is a stone filter. So, you recommend installing a water/fuel seperator? What is the difficulty level of this, what do I need, and are there any recommendations on the type.

Thanks for the replies.
 
Good work! Just a note here, a marine in-Carb filter is white plastic of some type (neoprene) I think, it won't deteriorate, it's not supposed to be paper.
 
MikDee said:
Good work! Just a note here, a marine in-Carb filter is white plastic of some type (neoprene) I think, it won't deteriorate, it's not supposed to be paper.
Click to expand...

You're right, MikDee. Looked like/felt like paper. I'm still going to replace it because of how bad of shape the gaskets were in. Any preferences for this filter?

Thanks
 
bajaboater said:
Got the carb inlet filter out. It was a mess, full of sand, old paper filter. The small gasket was basically non existent. Also, you are correct about the fuel filter. Took apart the fuel pump and found the filter with a rubber gasket. The filter is a stone filter. So, you recommend installing a water/fuel separator? What is the difficulty level of this, what do I need, and are there any recommendations on the type.

Thanks for the replies.
Click to expand...

Replace the "stone filter" if the carb filter is a mess, likely this filter is trash. You should never have to replace it again, ever if you install a separate filter.

Re: separate filter/separator

Two ways to go...

http://www.westmarine.com/buy/racor...-fuel-filter-water-separator-i-o-320r--484972

Gives you an easy way to check/drain water during season

http://www.westmarine.com/buy/sierr...rator-filter-replacement-element-kit--9399478

You have to remove filter and drain total contents ( fuel and water) into a safe container to use. Filters not designed for a high number of removal replacement cycles. Most folks just replace it whenever they check it, which gets expensive.

Links to West Marine above for reference only. Buy from your favorite supplier.


Level of difficulty.

Hardest past is finding a good place to physically locate it. Last time I installed one on one of my boats, I located it (mounted with two stainless "wood" screws and stainless washers) to a cross member in front of the engine, clear of moving parts. You need to find a place where you can drain the bowl ( if you go that way) or get a filter wrench on the filter body for the other way and remove/replace element. BTW. Spend the extra money and go to an auto parts store and buy a filter wrench that fits on the cap end of the filter body, not the strap ones if you go with the second choice. The "cap" ones are 3/8" drive and the handle you use is the same one you use for your wrench set. You will most likely be able to disconnect the fuel line from the inlet of the existing fuel pump and "swing" it over to the inlet of the filter/separator. You will need to fabricate a fuel line from the outlet of the filter/separator to the inlet of the fuel pump. Go to local marine supply store and buy enough USCG approved fuel line to reach from outlet of filter to inlet of the pump routed so as to clean all moving parts ( check diameter there are a couple of sizes), two hose barb to threaded male fittings ( again use correct size) and two stainless hose clamps plus two stainless screws and flat washers, the largest ones that will fit in the filter mount holes.
Reread my comments in post #2 about replacing the whole fuel line!

PS... since #2 choice filter and your oil filter are likely the same size, I'd pick up a 3/8 drive ratchet handle from an yard sale. Can often find a usable handle for $1.00. I keep mine on the boat, attached to a "cap" style wrench, all the time in a large ziploc freezer bag.
 
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