erikgreen
Captain
- Joined
- Jan 8, 2007
- Messages
- 3,105
Hey all... it's time to get my 21 footer out on lake superior again, and I'm still working on correcting a couple things from last year. Without further ado, let me say the engine doesn't give me the speed I would have guessed it would after I put it in almost two years ago now - it was a reman marine 350, and I used the intake, carb, fuel pump, oil pan, pulleys, and power steering pump and cooler off my old 305.
It DOES make RPMs between 4400 and 4600 with the current prop, a 17 pitch. Speed is about 44 mph on the gps. When I put on a 4 blade 23 pitch prop, I get RPMs about 4100 and about the same speed.
Although I am getting the RPM I think I should, here's Don's list of things to check, with my actions noted, because it's a nice summary:
List of possible causes of low WOT (Wide Open Throttle) rpm.
In no particular order
Engine Won't Reach Operating RPM. Check
1. Fuel condition. Type and Octane possibly old fuel
Fuel replaced last year with tank cleaned out, fuel stored with preservative, looks and smells ok.
2. Propeller pitch or diameter, damaged blades
Tried a couple diff. props, getting results as above. Blades are in good shape on one, new on the 4 blade, although the lower unit has no skeg ATM.
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
Checked that the carb is getting a lot of fuel, will pull the pick-up and clean soon. Fuel flow meter shows about 9GPH at full throttle.
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
Standard oil pan from the 305 installed, no windage tray, 5 quarts of 10-30 installed and will be changed out soon.
5. Marine growth on hull and outdrive
Freshwater boat, it's clean.
6. Wrong gear ratio in outdrive
1.5:1, from the old v8 engine
7. Restricted carburetor air intake (clogged flame arrestor)
I can see daylight through it, but it could use a wipe-down, so I'll do that and thoroughly spray it clear with brake cleaner.
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
Shutters are good, checked last year. Manifolds are old style logs, going to check for occlusion and rust soon. I'd love to convert to center rise, but don't have the cash right now.
9. Poor cylinder compression Compression Test
I'll be doing a compression check soon as preventative maintenance, but I expect numbers in the 150s or better - engine is just broken in.
10. Carburetor defective, or wrong type.
Carb is a Rochester Q-jet, from the 305, which I had thought was supposed to be a 750 CFM. So it should be ok on the 350? It seems to function, and I do get the rpms, but it's hard to adjust so I'd love to replace it and my intake with an edelbrock set at some point. In the interest of full disclosure the choke doesn't work, it was a spring type that I bought an electrical re-fit for but haven't installed yet. Choke is therefore always open.
11. Fuel pump pressure and vacuum
Fuel pump delivers a steady stream of fuel to carb. I haven't found any vacuum leaks or problems around the carb base yet.
12. Boat overloaded, improperly loaded, or improperly trimmed.
With just me in it, I don't go faster than listed above. The boat is a heavy one, it's a 1981 Sea Ray 21 footer that I re-did floors and stringers in. There's no wet foam left, but I may have added a couple hundred pounds by overbuilding it to compensate for missing foam weight.
13. Engine Overheating
Temps seem ok, confirmed manifold (intake and exhaust) temps with an IR thermometer. Gauge reports ok temp too.
14. Engine timing and ignition system operation
I set the timing with a timing light after I installed a new distributor rotor last year. I don't remember the setting off the top of my head but I think it was 4 degrees BTDC... my timing light doesn't do advance, but I checked the distributor weights to make sure it can advance, and verified with the light that it does.
15. Remote control cables and linkage for proper travel to open throttle plates fully.
I had a potential issue with this last year so I verified full travel. The throttle plates open all the way, or at least to their stops.
Soooo.... the situation is that I get the rated RPMs on my dash tach (dash tach checked against new tach last year, and will be replaced soon with new gauge set) but I don't get the speed I would expect.
I honestly don't care what the speed is as long as I'm getting what the engine can deliver and not somehow missing power I've paid for
My next steps for this boat are to perform spring maintenance, including checking plugs and new plug wires and probably new water hoses, then replace the gauges in the dash, then taking it out for a test run.
Thoughts on directions to go in would be appreciated. I'll post my test run data here as soon as I have it. I'm planning on running using the 17 pitch 3 blade prop.
Erik
It DOES make RPMs between 4400 and 4600 with the current prop, a 17 pitch. Speed is about 44 mph on the gps. When I put on a 4 blade 23 pitch prop, I get RPMs about 4100 and about the same speed.
Although I am getting the RPM I think I should, here's Don's list of things to check, with my actions noted, because it's a nice summary:
List of possible causes of low WOT (Wide Open Throttle) rpm.
In no particular order
Engine Won't Reach Operating RPM. Check
1. Fuel condition. Type and Octane possibly old fuel
Fuel replaced last year with tank cleaned out, fuel stored with preservative, looks and smells ok.
2. Propeller pitch or diameter, damaged blades
Tried a couple diff. props, getting results as above. Blades are in good shape on one, new on the 4 blade, although the lower unit has no skeg ATM.
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
Checked that the carb is getting a lot of fuel, will pull the pick-up and clean soon. Fuel flow meter shows about 9GPH at full throttle.
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
Standard oil pan from the 305 installed, no windage tray, 5 quarts of 10-30 installed and will be changed out soon.
5. Marine growth on hull and outdrive
Freshwater boat, it's clean.
6. Wrong gear ratio in outdrive
1.5:1, from the old v8 engine
7. Restricted carburetor air intake (clogged flame arrestor)
I can see daylight through it, but it could use a wipe-down, so I'll do that and thoroughly spray it clear with brake cleaner.
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
Shutters are good, checked last year. Manifolds are old style logs, going to check for occlusion and rust soon. I'd love to convert to center rise, but don't have the cash right now.
9. Poor cylinder compression Compression Test
I'll be doing a compression check soon as preventative maintenance, but I expect numbers in the 150s or better - engine is just broken in.
10. Carburetor defective, or wrong type.
Carb is a Rochester Q-jet, from the 305, which I had thought was supposed to be a 750 CFM. So it should be ok on the 350? It seems to function, and I do get the rpms, but it's hard to adjust so I'd love to replace it and my intake with an edelbrock set at some point. In the interest of full disclosure the choke doesn't work, it was a spring type that I bought an electrical re-fit for but haven't installed yet. Choke is therefore always open.
11. Fuel pump pressure and vacuum
Fuel pump delivers a steady stream of fuel to carb. I haven't found any vacuum leaks or problems around the carb base yet.
12. Boat overloaded, improperly loaded, or improperly trimmed.
With just me in it, I don't go faster than listed above. The boat is a heavy one, it's a 1981 Sea Ray 21 footer that I re-did floors and stringers in. There's no wet foam left, but I may have added a couple hundred pounds by overbuilding it to compensate for missing foam weight.
13. Engine Overheating
Temps seem ok, confirmed manifold (intake and exhaust) temps with an IR thermometer. Gauge reports ok temp too.
14. Engine timing and ignition system operation
I set the timing with a timing light after I installed a new distributor rotor last year. I don't remember the setting off the top of my head but I think it was 4 degrees BTDC... my timing light doesn't do advance, but I checked the distributor weights to make sure it can advance, and verified with the light that it does.
15. Remote control cables and linkage for proper travel to open throttle plates fully.
I had a potential issue with this last year so I verified full travel. The throttle plates open all the way, or at least to their stops.
Soooo.... the situation is that I get the rated RPMs on my dash tach (dash tach checked against new tach last year, and will be replaced soon with new gauge set) but I don't get the speed I would expect.
I honestly don't care what the speed is as long as I'm getting what the engine can deliver and not somehow missing power I've paid for
My next steps for this boat are to perform spring maintenance, including checking plugs and new plug wires and probably new water hoses, then replace the gauges in the dash, then taking it out for a test run.
Thoughts on directions to go in would be appreciated. I'll post my test run data here as soon as I have it. I'm planning on running using the 17 pitch 3 blade prop.
Erik
