What do I check next?

[adimice]

A while back this post was asking about a 260hp 350 merc not being able to sustain high rpm 3000+. I've had the same problem. I got a new fuel pump new coil, spark plugs and wires. It runs great at low rpms but than quits completely. Then bluecollarboater said he had the same prob and it ended up being broken spring on the centrifigal weights in the distributor. I checked mine, they aren't broken, but one spring is much less hefty than the other, is this normal, is one a return spring and the other an advance spring. Can anyone help. Thanks

 

[Don S]

Re: What do I check next?

They do have different sized springs in the distributor. Mind giving us a year or better yet a serial number for your 350 Merc? Lots of different ignition systems used over the years.

 

[D Hickerson]

Re: What do I check next?

Mine was doing the same last year. My boat sat for to long and the carb got gummed up. I ended up sending the carb for rebuild from an online service. Great results and cost me about 150 bucks. I was doing the same thing you were doing...throwing good money at the boat with no results.

 

[adimice]

Re: What do I check next?

It appears to be a 1986-1990 350 4 bolt main, serial #5384702. Prestolite distributor JMS 65-189

 

[Don S]

Re: What do I check next?

What year is your boat? That serial number is not Mercruiser, and from 86-90 merc didn't use 4 bolt mains nor did they use points or electronic distributors with mechanical advance. So obviously the engine was changed, perhaps we can track down which distributor you have.

 

[adimice]

Re: What do I check next?

Hey Don, It's a prestolite distributor 855932 DU 780112B. The boat is an Albemarle 1983 it has a chey 5.7L . The painted over valve covers said mercruiser with that 5384702#. Someone on this site told me the block #14101148 was an 86-90 4 bolt etc. I really don't now what engine I have, it's got volvo penta stuff bolted on, like the thermostat housing. I thought the original volvo engine died and was replaced with a mercruiser, which is just another chey 5.7 350 , then someone put all the volvo stuff on a merc. I appreciate you help.

 

[Don S]

Re: What do I check next?

Ok, now we are getting somewhere. It's a Volvo distributor, someone replaced the block with a Mercruiser engine, but used the Volvo accessories. I'm going to do some looking and will post back.

 

[Don S]

Re: What do I check next?

To answer your original question, those springs are different, and it's normal. Different springs give different advance curves.
You should be setting your timing at 8? at 650 rpm, and then seeing 25? at 3000 rpm with probably a few more at wide open throttle, but 3000 should be the test rpm.

BUT, there are a lot of other things that can cause low wot rpm.

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

 

[adimice]

Re: What do I check next?

Hey, I didn't have low WOT, I had no T. The engine would shut down, no sputtering, no missing no coughing, just shut down. It would start again after a while, couple of minutes. I didn't think lack of proper advance would shut it down. That's why I changed the coil. I haven't been able to get to big water to run it with the new coil. When I heard about the broken spring, it got me to looking at other possible reasons for a shutdown. I run the outdrive in a good size tub , with a hose on all the time. It runs like a swiss watch in the tub.

 

[Don S]

Re: What do I check next?

Hey, I didn't have low WOT, I had no T. The engine would shut down, no sputtering, no missing no coughing, just shut down.

you forgot to mention that minor tidbit. All you said is it would not hold sustained rpm over 3000.

Sounds to me like you have fuel delivery problems. Do you get fuel from the accelerator pump holes when you operate the throttle with the engine not running?

 

[adimice]

Re: What do I check next?

Yes

 

[Bondo]

Re: What do I check next?

Hey, I didn't have low WOT, I had no T. The engine would shut down, no sputtering, no missing no coughing, just shut down. It would start again after a while, couple of minutes. I didn't think lack of proper advance would shut it down.

Ayuh,... I donno how those ole Volvos are wired, But,...
During the No start/ No run situation, You need to check for voltage At the coil's (+)....
My guess is, it ain't there....
It's gettin' lost between there, 'n the keyswitch...