Volvo 280 sterndrive on 2650-gctid825788

[rmitch]

Just launched the 2650 after she set in barn for over seven years. I did all the service items and ran her with a muff before launch, the engine, the ISUZU 4BDI started and ran well. On launch, had some issue with the drive kicking up in reverse, but after running up trim up and down the lock held. After careful warm I ran the engine up and we comfortably ran at 1700 rpm and 6 mph (GPS), which is approximately hull speed. When I ran the engine up to 3000, which is the engine rated speed, she came up to 9 mph. It easily went to 3000 and could have gone more but I was out of Tach and being careful of an engine that sat for seven years. I suspect the prop is pitched to fine. This engine is capable of 80-100 hp and should take this boat on plane. Boat weighs about 5500.

The 280 outdrive has a tag on it, 284 9029 D, the propeller is a 15 inch, 3 blade. and no numbers for pitch, (I removed and looked at the hub) does anyone know the sterndrive ratio that might help me start figure out what the boat should have in order to plane? I will not operate the boat in plane often but would like to know I could if needed.

[pmhinpc]

Being that it is a D after the serial number it is a 2.15 to 1 ratio.

[rmitch]

I just found under the zinc forward of the propeller a stamp saying 2.15. With two sources, I think that is what I have. According to Boatdiesel.com prop calculator, with a 2.15 ratio, I need to run the 16 in prop with a 23 pitch. Now I have a 16 with a 17 pitch so that explains running out of prop before I ran out of motor. Is it correct that the 2.15 ratio was used on diesels in order to stand the torque?

[2850Bounty]

"rmitch" post=825822 wrote:
I just found under the zinc forward of the propeller a stamp saying 2.15. With two sources, I think that is what I have. According to Boatdiesel.com prop calculator, with a 2.15 ratio, I need to run the 16 in prop with a 23 pitch. Now I have a 16 with a 17 pitch so that explains running out of prop before I ran out of motor. Is it correct that the 2.15 ratio was used on diesels in order to stand the torque?

[color]blue wrote:
In the standard AQ series s/p lower units, the 2.15:1 is of the greatest reduction.

In order to gain this reduction, the lower unit's "drive" gear is of the smallest diameter (between the 2.15:1, 1.89:1 and 1.61: 1 ratios)

This means less gear tooth contact at any given time....... of which equates to the weakest of the reduction gear options.

As the reduction is decreased (taller gear set), the "drive" gear become larger..... this means more gear tooth contact at any given time..... of which equates to a stronger gear set!

(ask a young kid who immediately went out and bought low reduction ring/pinion gears for their off-road rig.... only to learn that these break more easily)

So in theory, if you went to a 1.89:1, or even the 1.61:1 lower unit, you will be able to pitch down some and get away from the 23 pitch.

.[/color]

[rmitch]

I appreciate what you said about the gear loading and since we are going to use this boat on rivers, I need as much help there as I can get.

According to Boatdiesel prop calculator, if I had a 1.89 ratio then I would need a 16 in by 19 pitch, which is a lot closer to what I have, a 16x17, the prop shop says they can re-pitch what I have to a 19. Now, the question is how I change the ratio, according to the Clymer manual I have, I need to remove the sterndrive from the boat then remove the upper housing and split the intermediate from the lower, Is that correct? Are the ratio gears available?

[dmcb]

From what I can see your engine should be 2200/2400 rpms at wot.

You should gear and prop to reach that number.

Doug

[rmitch]

The engine I have is a Isuzu 4BDI, and according to tech sheets from the PO (QD-100 tech sheet) it makes intermittent 88 hp at 2800 rpm and continuous 78 hp at 2800 rpm. It reached 2800 easily and even 3000 easily under way and because some data sheets list it as 3000 WO and because we zipped right past 2800 with no load noticed on the engine I knew I had a prop pitch too "fine". I intend to prop it for 2800 (or close) Now, what to do is the question. I can tweak this prop to a 20 pitch but that is only half way there or I can try to change the ratio to 1.89 in which case my reworked prop will work fine.

[2850Bounty]

"rmitch" post=825985 wrote:
The engine I have is a Isuzu 4BDI, and according to tech sheets from the PO (QD-100 tech sheet) it makes intermittent 88 hp at 2800 rpm and continuous 78 hp at 2800 rpm. It reached 2800 easily and even 3000 easily under way and because some data sheets list it as 3000 WO and because we zipped right past 2800 with no load noticed on the engine I knew I had a prop pitch too "fine". I intend to prop it for 2800 (or close) Now, what to do is the question. I can tweak this prop to a 20 pitch but that is only half way there or I can try to change the ratio to 1.89 in which case my reworked prop will work fine.

[color]blue wrote:
It is difficult to pitch your way out of an incorrect over-all gear reduction. It seldom works.

Here's my suggestion:

1....... Do not purchase an expensive gear set and bearings with the intent of changing the over-all reduction. This is also Hypoid gear work that will need to be left to an experienced Pro!

2...... Instead, look on e-Bay for a 1.61:1 lower unit....... or...... look for a less-in-demand 1.89:1 ratio lower unit.

Be sure to ask the seller to include the tapered roller bearing "race" that should be sold with it !!!!!!!

3...... See your OEM work shop manual for an explanation re; the A and B dimension which will allow you adjust the (above the race) shim value prior to installing the replacement lower gear unit.

Be sure to replace all O-rings.

4...... add your 30W non-detergent oil, and go test it out!

Here is one from behind a V-6. The seller is not sure of the ratio.

You could ask the seller to pull the ring anode and look for the numbers!

It may be either a 1.89:1 or a 1.61:1

http://www.ebay.com/itm/Volvo-Penta-...FZylyo&vxp=mtr

Here is another one. Seller says that it's a 1.89:1 reduction from a V-6 application, of which may be right for you.

It is a C drive and will have the shorter vertical shaft. This means that you will need the long spline coupler..... and again, don't forget to ask the seller to include the tapered roller bearing race that should go with it !!!!!!.

http://www.ebay.com/itm/Volvo-Penta-...hXQpme&vxp=mtr

Use caution. Many of the sellers using e-Bay don't have a clue as to which Volvo Penta parts they are actually selling.

Good luck with the project! [/color]

[rmitch]

I ordered the 1.89 leg from freshwater volvo, (one of the links you gave me) he threw in the spline and the bearing race is attached to the prop. Hope I get it installed before the weather turns, we just had 6 in of snow, which all melted but tells you what is on the way.

[rmitch]

Bearing race is wired to prop shaft, the spline connector is the long connector as this is a short shaft unit as I understand it and I need it for my set up. The vendor understood exactly what I meant when I ask for the bearing race,(because I don't) and he said he had an long splice (connector) he would throw in. I will re-read the section on shimming but may have questions going forward. I thank you so much for all the help so far.

[rmitch]

Upon receiving and inspecting the the lower leg, the upper bearing race was slightly "watermarked" in one place, I can feel the edge of the discoloration with my fingernail, and the bearing rollers looked a dark grey. I am concerned that the bearings I can't see may be in a similar shape. Am I being overly concerned?

The leg was stamped with 1.89 so it is the correct ratio and the spline connector was attached.

[2850Bounty]

Am I being overly concerned?

No...... I too would be concerned!

.

[rmitch]

Last Oct I took the boat with the new (to me) 1.89 outdrive to Great Falls Volvo service shop. They removed the old leg(2.15 ratio) and installed the new (1.89 ratio), replaced bearings, adjusted pre load and pressure checked and serviced with hyd fluid. They said I needed a spacer, that what was on the old leg would not work. I am now trying to figure out what spacer I need. I have a picture of the new shaft. and I think it is a 275 due to the configuration with the hole in the end of the shaft for the locking bolt.

[Yendrabuilt]

My Volvo drive and prop combination uses the prop cone nut without the spacer and the spare nut I had came with the spacer pressed on it, so if you buy a new nut the seller may ask with or without spacer. That Isuzu is a great engine, I worked at an Isuzu truck dealer and one of the NPR trucks went to 480,000 miles the owner was disappointed he wanted to make 500K!

[rmitch]

Yendrabuilt, thanks for the response, I bought a short spacer online but the rear of the prop still stood off the zinc casting a good 1/4 + ". I machined off .220 from the inside of the spacer on the new spacer and that allowed the prop to slide further on the shaft so I now have full spline engagement (with some space to enable tightening) and the space between the prop (with line cutter) and the zinc casting is about 1/8, which visually looks better. This also allows a few more threads engagement on the prop cone nut which should be better. I don't know why I had this spacer problem, I had both spacers, long and short and the shortest was too long, but now it seems to be ok. So far I am very happy with the Isuzu.