'90 90 hp Still having problems!

[bbfrs1]

My max rpm is about 4000. And it take more than 30 seconds to get there. It is on a 18' Capri. I know it is underpowered but I should still be getting around 5400 rpm. I have great blue spark, replaced fuel diaphram, checked all my hoses, replaced spark plugs, and my compression is all 128#. I had a mechanic go through the carbs and he said that they looked good. It seems like a fuel problem to me but I'm not sure. If anyone has any suggestions I would greatly appreciate it.

 

[pnwboat]

Re: '90 90 hp Still having problems!

What are the specs. on your propeller? Diameter and pitch?

 

[bbfrs1]

Re: '90 90 hp Still having problems!

Its a cupped 13x15 pitch

 

[john from md]

Re: '90 90 hp Still having problems!

A cupped 15 pitch prop will act like a 17 pitch prop. You still should be getting higher rpm.

You haven't said anything about timing or if you have decarbed the engine recently. Retarded timing will give less power as will sticking rings. Your compression is low so give it a good decarb and see what happens.

John

 

[Bigprairie1]

Re: '90 90 hp Still having problems!

What is the condition of the boat like? Any water in the bilge? Rebuilt floor....or poor floor condition?
If your boat has a lot of additional weight because of water in the bilge or absorbed water into the hull foam and wet/rotten stringers etc you might be trying to plane a 2000+lb boat instead of a 1400lb boat.
If the boat is usually trailered try to get a weight off a local scale the next time you are out and you can rule that out of the equation.
Note: I've got the exact same motor/boat set-up with very similar compression and with a 17pitch prop. It gets up and goes reasonably well for a 19 year old boat/motor.
(speed: high 30's to maybe 40mph, with revs at approx. 5400-5500rpm)
As John said, go through the timing procedure. As well, make sure your throttle/carbs are opening up fully. If they linkage is out of adjustment you might only be pushing 3/4 throttle (or less).
I believe the manual covers this procedure and check.
Good Luck.
BP

 

[bbfrs1]

Re: '90 90 hp Still having problems!

I did just decarb the motor. I took it out again today, and I have to snowly put it past gear or it will die. But if floor it, it will die as well. It really likes half throttle. The boat is in great condition, the hull is great. While on the water for 4 hours the bilge will barely pump out any water. What is best way to check the linecage, when I tried to check it all the carbs looked the same as far as wings open. Sorry for lack of better term. And also my mechanic said the timing was good, but now I don't know how reliable he is. There is no good Force mechanic in Idaho that I can find

 

[roscoe24]

Re: '90 90 hp Still having problems!

I'm no boat whiz. my certified force mechanic told me these motors should be pushing about 160 lbs of compression mine pushes about 125# runs descent but not like it did when it was overhauled 8 years ago

 

[bbfrs1]

Re: '90 90 hp Still having problems!

It basically boils down to a timing or carb problem. I took it out today and should have used 10 gal. of fuel and only used 3 gal. I just don't think it is getting the fuel it needs. I have never been around an outboard of this size but my 20hp will be at wot in 5 seconds no matter what the load is. My 90hp Force should do the same. But I could be wrong.

 

[john from md]

Re: '90 90 hp Still having problems!

bbfrs1,

Since you have tried a few things and have not isolated the problem, try this method. With the engine running at idle, using a glove of some sort, pull off one plug wire at a time to see how it affects the running of the engine. When you put the wire back on , wait a minute or two before pulling the next wire. If you pull one off and the engine doesn't loose power, that is the cylinder that is causing your problem.

You don't need a mechanic to do this, just follow my instructions. Let us know what your find. Be patient troubleshooting from a computer key board takes time.

John

 

[roscoe]

Re: '90 90 hp Still having problems!

what do the plugs look like?

Where are you located? Idaho ! at what elevation? Where did you get the boat from.
Elevation makes a big difference. If the previous owner had the carbs rejetted, you may have the wrong jets in the carbs.

Or, if it has the factory jetting, you will need to rejet for elevation.

What happens if you bump the choke, or hold it in for 1 second bursts? Does it die?

 

[bbfrs1]

Re: '90 90 hp Still having problems!

I'm about 4800ft. The boat has always been in Idaho but the elevation was is about 2500ft where it came from. When I push in the choke it dies immediatly. The plugs are brand new and I just decarbed so they are still silver.

John, I will try the plug test tomorrow and let you know how it goes.. Thanks everybody.

 

[roscoe]

Re: '90 90 hp Still having problems!

Factory main carb jets were good to 2500'.

2500-5000' used .072 in the top carb, and .070 in the middle and bottom carbs.

5000-7500' used .070 in the top carb, and .068 in the bottom two carbs.

 

[john from md]

Re: '90 90 hp Still having problems!

If you don't know what jets you have in the carb you can get a mirror and look at the bottom plug if it is a bottom jet type or pull the bowl off one and look at the side jet. All the jets have the size stamped on them.

John

 

[ezez]

Re: '90 90 hp Still having problems!

I'm about 4800ft. The boat has always been in Idaho but the elevation was is about 2500ft where it came from. When I push in the choke it dies immediatly. The plugs are brand new and I just decarbed so they are still silver.

John, I will try the plug test tomorrow and let you know how it goes.. Thanks everybody.

I run my 1991 Force 90HP up at Cascade, ID (4800 ft) without any issues. I believe my jets are the standard size...The upper and bottom carbs have a .076 main jet screw and the middle carb has a .074 main jet screw.

I'm not an expert but I would recheck your fuel pump diaphram and fuel lines. I know you said you replaced the diaphram but something doesn't seem correct. After that I would work your way into the carbs checking the jet sizes, etc. If you have the ability to check the timing advance do that as well but I doubt that is your issue. Regardless ensure the carbs are all synced together and with the timing advance. After ruling out the fuel issues than you need to start considering the ignition system.

 

[bbfrs1]

Re: '90 90 hp Still having problems!

I just tried the spark plug test. When I pulled a wire off it would die but definately made it run worse. All three wires did the same thing. I pulled the air intake to check if the carbs were the same. I shifted into gear and they would go just past open flat, all at the same time. The trigger would advance as far as it would go. I tried moving it with my thumb and it wouldn't move.
The vaccuum line in the bottom of the air intake was completely plugged.. Would this run my timing advance like on a truck. I cleaned it out. And will wait to see what everybody thinks before I go any further.

Also, where in the heck are the fuel filters on this boat. The only one I can find is on the fuel pump and its just a screen. I would imagine the sending unit would have one.

 

[bbfrs1]

Re: '90 90 hp Still having problems!

my jets are all .070.

 

[john from md]

Re: '90 90 hp Still having problems!

The plugged recirculation line would allow the lower cylinder to get too much fuel. This will cause the engine to bog. A hole in the fuel diaphram will do the same thing.

John

 

[pnwboat]

Re: '90 90 hp Still having problems!

Timing advance is done by mechanical linkage. No vacuum involved like an automobile.

The vacuum line that you are referring to, does it go between the bottom of the cover that goes over the carbs? If so, this just sucks off any fuel/oil residue that collects in the bottom of the cover.

The only fuel filter is the screen in the fuel pump. It's a good idea to install a cheap inline filter between the pump and carbs for added insurance.

Do you have the small fuel pump that kind of looks like it's shaped like a figure eight? If so, there are three check valves inside that sometimes get sticky limiting the amount of fuel. Cheap easy fix.

Several additional things to check if fuel is flowing properly.

Does your primer bulb get hard after squeezing 3 or 4 times? If so, then needle valves in carbs are working properly. If not, then either bad needle valve, or float set too low.

When you give it the gas, does the primer bulb go flat? if so, then there is blockage in the fuel pickup in the tank, or your fuel tank vent line is plugged up.

Does squeezing the primer bulb when at WOT help at all?

 

[bbfrs1]

Re: '90 90 hp Still having problems!

My fuel filter was plugged. I could barely blow through it. There was also dirt in the bottom of the top carb bowl. Is it difficult to clean the jets out. I'm thinking they might be plugged now.

While at wot squeezing the bulb didn't help. And it doesn't go flat when i get into it. I already checked those things. It usually takes 4-5 times to prime the bulb. I have to replace the little fuel line at the bottom of the pump, so I couldn't prime it again.

 

[john from md]

Re: '90 90 hp Still having problems!

If you are careful, you can clean the main jet with a paperclip. For the interal passeges of the carb, if you don't have an air source, use carb cleaner in a can.

John