3GM30F Injector Questions

[Stretch]

The engine is a 1991 model that had 960 hours on it in 19 yrs. I put 300 on in 2 seasons and it was always a bear to start. Like Stem to Stern says, get used to it.It ran well otherwise. A few good tips from you all here helped alot, like full throttle and a little heat on the intake side ofthe block on cold mornings in the off season. Have had the injectors removed and rebuilt by NW Inj as they are likely the originals. One of the PO damaged the no3 and it likely has not been off since. The mechanic got it out and NW was able to save it. Pressure tested low on all injectors at idle. 330 or so.
My question,
I assume the gasket slippage is from the removal, not a bad owner install, would you concur?
Is that stain on the side of the injector blow by? Poor install?

Injjector No3 is strip and stain,
no2 stain,
no1 appears clean and firing well.

The picture start with the no3 2 pics , no2 2 pics and no 1 , 1 pic.

The engine made 3000rpm on the original gauge[suspect] when I purchased it, with a clean hull, however, I suspect I may be overpropped with a 16x13 3 blade on my H35.5.

Thanks for your comment
Stretch

 

[Warren Milberg]

Is your engine also hard to start after running it for a while, shutting down for some hours (like while you are day sailing), and then starting up to go home? Have you looked at the quality of your fuel and (1) ensured it is "fresh," (2) has no water or bugs in it, and (3) has a minimum cetane rating of at least 45? A lot of diesel fuel sold these days is only rated at 40 cetane and that could make starting more difficult. I assume you have good compression, clean primary and secondary fuel filters, and unobstructed air going into the engine....

 

[anchorclanker]

Are you saying compression was 330 PSI? 960 hours in 19 years, thats only 50 hours a year. Lack of use and poor service could have carboned up the rings. MMO may help, or run a can of Gunk Motor Flush in it just before an oil change (directions on the can). Then put some hard hours on it.

Over propped could be killing it though. And its not enough to just throttle back, too much prop has the engine working too hard across the whole range. I would check it out and correct it if thats a problem. You want the engine to reach full rated RPM, not be lugged down. Make sure your using a trusted tach

 

[rocksculpter]

I'd say you are overpropped, you should easily hit 3400RPM with that engine. Some folks would run at that as cruising speed. I have the 2gm20f, same injectors, on a 12,000 lb boat and running a 14 X 11. I had it repitched to that on recommendation of the Prop Shop in Lynwood, Wa.

I'm curious to find out how much it cost to refurbish your injectors. I've seen new ones at about $130, I can't verify that right now. New operating injector pressure is about 2800psi.

 

[Stretch]

wow what a difference!!!!

We primed and bled the fuel lines and she started right up I didn't need the full throttle like before. What a difference in idle quality, no smoke show on startup. It is startling how much better the performance is.
Before it would shake on the lowest idle rpm even warmed, like the engine mounts were marshmallow, and I would have to increase the throttle speed.It would restart the same day with one revolution, but I could not motor immediately as it would shake bog and stall on engaging forward. Same if I tried to leave the dock too early after anovernight stop, if it didn't warm up 10 min it would choke and stall out, black exhaust residue on gear engage and throttle up. Warm, it would be an angel, and shift fine. In some seaway, itwas starting to run poorly above 2200 rpm. The fuel tank was drained and new fuel installed this June. Filters new too.
The sea trial today on the new injectors was impressive to, with the engine revving quicker, the .engine rpm sweet spots wider and after 20 min, full throttle, with 3000 rpm indicated on the original 1991 gauge. The prop did not feel like it was bogging the engine. We made 6 knots at just over2000 rpm indicated and 6.8 wot. There was not black clouds from the 5 min burst at wot and just some minor steam in the exhaust from the cool 35 deg temps up here today. The temp maxed out at 160 deg and quickly returned to 125 after throttle down.
I was very happy with the results today and wondered why I didn't do this sooner. It was would have been easier onthe engine too. I suggest this to anyone who has experienced the same problems. I had been adding fuel stab cleaner from Racor per directions all year and noticed no benefit. Cleaning out the fuel tank made more difference.