TOPIC: ok to love my 1500?

my resto on my '68 maritime is underway and the question of power will rise sooner or later... here's where i stand. i have a strong 1500 merc. '74 model. pros i love these motors mine is in great shape. all cowlings insulation and general stuff is perfect fires right up and has never left me... cons wiring is looking like a time bomb tilt and trim pump leaks down while driving and mainly the motor has not liked to run wot since ethanol has been added to gas. even when running "non ethanol" this motor will bog and run out of fuel at wot. runs great at 3/4 and below. dunno if i should consider a repower or try to remedy my woes...

sounds like it needs a thorough serviceing.
check timing and synch, clean and rebuild your carburetors, clean and install new fuel pump kits, plugs, make sure you compression is good and even maybe even do a leak down check to check the health of the cylinders
as far as the tilt and trim go back and be sure all the fittings asre snug. do be rough on them you will strip them. If they are snug then replace the hoses and there are o-rings under the manifold the hoses attach to on the pump.

Ditto what Jim said, but be REAL careful snuggin up those trim hoses on the pistons. Steel fittings going into aluminum are very easy to strip out. Trust me, been there, dun that.

Once you've rebuilt the carbs and fuel pumps, there is no need to worry about ethanol anymore as long as there are products like Marine Formula STA-BIL® Ethanol Treatment. You can't beat this stuff, and it is commonly available.

Best of luck to you!

Frank

already done the carbs and switched to an electric fuel pump with no change. i read somewhere that a bigger wot jet wld help? i will add that while i still have the problem with "ethanol free" id does improve considerably. wot is a real dog with 10% ethanol. also rebuilt the cylinders so i know my trim issues r pump related. grew up on these motors and have always run them. drove to ohio from sc to buy this on because of its condition about 7 yrs ago. had no problems the first 2 yrs. this engine was in storage for 13 yrs prior to my purchase. thanks for the interest and replies. seems like a great resource for old bout junkies like me

Depending on the electric fuel pump you have it may not be enough. The electric I run on my 1150 is not enough for the 1500 I run. You are further ahead with the double chamber pulse driven pump. It pumps on every pulse/push pull. If you have not already reduce your timing to 20 or 21 degrees, not the 23 on the sticker. Check your jet size, should be at lease .082.

Just my 2 cents.

thanks. pump was changed as a first attempt at remedy. no diff at all. pump rated at 90 gallons per hour 2-3psi. i read somewhere that main jets were often .081 and changing to .082 helps with this issue so u may be on the right track. this motor was in storage for quite a few years so no modern tricks have been applied. i have replaced all the fuel lines. got several other projects goin on with this boat but i will pull jets asap and check em. i also have not checked the timing so it will go on the list as well. i am a pretty fair shade tree so i hope i can resolve my beloved merc. anybody ever used a trim pump from a mercruiser? they seem plentiful and cheap.... thanks for the .02

You say wiring looks like a time bomb, this is a typical problem.
I'd fix it. The thunderbolt ign needs good connections. The higher the RPM the more amps that are needed through the wires. You may be limited by a corroded wire. New internal wire harnesses are available from Merc. If the outside one is junk they are hard to repair as wires are often too fragile to solder to. Look at ebay for a control with good cabling and if the stator wires are junk look to ebay for this.
The trigger wires have to be GOOD too, there are aftermarket avail or ebay again.
Take cap off dist and make sure center contact is good and there is not carbon tracking between the posts, clean the inside of the cap with Brake clean or other fast evaporating solvent. run the motor at night and look for arcing of the ignition wires.
Stock jets are 080. on a long shaft. If you are running it hard go to 082, these are availanble from Merc. Retard timing to 21 degrees...ONLY USE premium gas, it's CHEAP insurance against catastrophic detonation. Ethanol should not make a wit of difference if motor is right BUT, check for water in your ethanol fuel source. If you redid carbs and did not get the needle levers adjusted right then no matter what, your mixture will be wrong regardless of jet size, fuel height in the bowl is critical for correct fuel mixture adn these levers set it, re check if in doubt, there is a closed height and a drop height adjustment on the levers.
Make sure water pump is good, poor cooling will be an issue at higher RPM's as motor will start to run hot....very bad!
Squeeze bulb while running to boost fuel, if no difference that's not it.
Make sure you chioke plates are fully retracted.
If the pump is leaking at the seat where the hose nut connects, over tightening will not work. Make sure it's not at a hose crimp fitting. Hand thread the nuts to start, easy to cross thread if you force the first few turns with a wrench. Wiggle the steel tube while hand turning nut keep tube in straight to start the thread. Mercruiser does not have 4 hose connections.
Randy

At WOT the 1500 needs a minimum of 4.5 psi to keep the fuel bowl full. I determined this by using an inline pressure regulator and test and run, test and run etc. For example, my electric fuel pump, marine, 4 to 7 psi is just enough to run my 1150 and not enough to run the 1500.

Are you guys pulling from tanks located a great distance from the motor?


I have yet to have an issue with the stock fuel pumps on a merc as long as they are working well.

Conrad

thanks for the advice. performance is unchanged from stock fuel pump to electric so i am assuming its not pump related. the problem is however affected but not remedied by tank changes. the problem is more pronounced by those cheap attwood 6 gallon tanks from walmart. the ones with the flexible small pickup. i have a 24 gallon large tank with a 3/8 pickup that seems to help slightly. i have also run a small 3 gallon merc tank elevated for some gravity feed and the symptons were improved even more. i think it is most likely fuel related. the mercruiser pump has a manifold that splits to 4 lines under the outdrive. didnt know if i cld use that. i have not approached it from an electrical standpoint yet. i def notice some corrosion and cracked insulation on some wires. i will add that when u ram wot the motor does rev fine at first and then seems to run out of fuel after about 10 to 15 seconds when bowls empty i assume. been using it this way for quite a while i just dont run wot but i want my merc back! boat cruises about 35 mph without issue. thanks again for all the suggestions and mainly some encouragement to not give up on my tower of power!

The stock pumps are fine Conrad, in my case I am pushing 2000 pounds of boat,motor,fuel,3 batteries, full live wells, fishing gear, two people, food and liquid for a full day of tournament fishing, extra fuel and so on. Sometimes you just need a little more fuel. Thats why I experimented with the electric pump.
For you its easy...motor, boat, you, camera,fuel.

picked up some .082 jets. will address wiring and check timing. got some other boat projects goin so might be a couple weeks. i'd really like to get my trim wrkn properly. it works fine at low speeds but leaks down quickly above 20 mph. any ideas???

Power trim shouldn't be affected by speed. Sounds like air in the lines or something trim related. I'd bleed the system to make sure.

Frank

def in the pump. did this when i had an 80 hooked to the same pump and i have replaced seals in the cylinders. the motor will lift when under power but leaks down almost immediately. apparently these are very difficult to rebuild...

Bah! Good luck with it.


Frank

I do not see why a mercruiser trim pump would not work.Might need some slight mods in the lines,a trim pump is a trim pump,two cylinders that go in and out...........

just take the bottom off your pump and put it on a mercruiser pump they are the same except for the valve body.

thats what i think im gonna do. anyone tried thicker oil??

went to rejet today and i think my original 080 jets have been drilled. they seem to be slightly larger than the new 082s i just bought.